mirror of
https://github.com/KhronosGroup/SPIRV-Tools
synced 2024-12-01 23:40:04 +00:00
d35a78db57
Fixes #4960 * Switches to using enum classes with an underlying type to avoid undefined behaviour
1040 lines
45 KiB
C++
1040 lines
45 KiB
C++
// Copyright (c) 2020 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include "source/fuzz/transformation_flatten_conditional_branch.h"
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#include "source/fuzz/fuzzer_util.h"
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#include "source/fuzz/instruction_descriptor.h"
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namespace spvtools {
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namespace fuzz {
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TransformationFlattenConditionalBranch::TransformationFlattenConditionalBranch(
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protobufs::TransformationFlattenConditionalBranch message)
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: message_(std::move(message)) {}
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TransformationFlattenConditionalBranch::TransformationFlattenConditionalBranch(
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uint32_t header_block_id, bool true_branch_first,
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uint32_t fresh_id_for_bvec2_selector, uint32_t fresh_id_for_bvec3_selector,
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uint32_t fresh_id_for_bvec4_selector,
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const std::vector<protobufs::SideEffectWrapperInfo>&
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side_effect_wrappers_info) {
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message_.set_header_block_id(header_block_id);
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message_.set_true_branch_first(true_branch_first);
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message_.set_fresh_id_for_bvec2_selector(fresh_id_for_bvec2_selector);
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message_.set_fresh_id_for_bvec3_selector(fresh_id_for_bvec3_selector);
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message_.set_fresh_id_for_bvec4_selector(fresh_id_for_bvec4_selector);
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for (auto const& side_effect_wrapper_info : side_effect_wrappers_info) {
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*message_.add_side_effect_wrapper_info() = side_effect_wrapper_info;
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}
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}
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bool TransformationFlattenConditionalBranch::IsApplicable(
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opt::IRContext* ir_context,
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const TransformationContext& transformation_context) const {
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auto header_block =
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fuzzerutil::MaybeFindBlock(ir_context, message_.header_block_id());
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// The block must have been found and it must be a selection header.
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if (!header_block || !header_block->GetMergeInst() ||
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header_block->GetMergeInst()->opcode() != spv::Op::OpSelectionMerge) {
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return false;
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}
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// The header block must end with an OpBranchConditional instruction.
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if (header_block->terminator()->opcode() != spv::Op::OpBranchConditional) {
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return false;
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}
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// The branch condition cannot be irrelevant: we will make reference to it
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// multiple times and we need to be guaranteed that these references will
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// yield the same result; if they are replaced by other ids that will not
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// work.
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if (transformation_context.GetFactManager()->IdIsIrrelevant(
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header_block->terminator()->GetSingleWordInOperand(0))) {
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return false;
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}
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std::set<uint32_t> used_fresh_ids;
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// If ids have been provided to be used as vector guards for OpSelect
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// instructions then they must be fresh.
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for (uint32_t fresh_id_for_bvec_selector :
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{message_.fresh_id_for_bvec2_selector(),
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message_.fresh_id_for_bvec3_selector(),
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message_.fresh_id_for_bvec4_selector()}) {
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if (fresh_id_for_bvec_selector != 0) {
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if (!CheckIdIsFreshAndNotUsedByThisTransformation(
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fresh_id_for_bvec_selector, ir_context, &used_fresh_ids)) {
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return false;
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}
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}
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}
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// Use a set to keep track of the instructions that require fresh ids.
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std::set<opt::Instruction*> instructions_that_need_ids;
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// Check that, if there are enough ids, the conditional can be flattened and,
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// if so, add all the problematic instructions that need to be enclosed inside
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// conditionals to |instructions_that_need_ids|.
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if (!GetProblematicInstructionsIfConditionalCanBeFlattened(
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ir_context, header_block, transformation_context,
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&instructions_that_need_ids)) {
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return false;
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}
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// Get the mapping from instructions to the fresh ids needed to enclose them
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// inside conditionals.
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auto insts_to_wrapper_info = GetInstructionsToWrapperInfo(ir_context);
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{
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// Check the ids in the map.
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for (const auto& inst_to_info : insts_to_wrapper_info) {
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// Check the fresh ids needed for all of the instructions that need to be
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// enclosed inside a conditional.
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for (uint32_t id : {inst_to_info.second.merge_block_id(),
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inst_to_info.second.execute_block_id()}) {
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if (!id || !CheckIdIsFreshAndNotUsedByThisTransformation(
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id, ir_context, &used_fresh_ids)) {
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return false;
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}
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}
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// Check the other ids needed, if the instruction needs a placeholder.
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if (InstructionNeedsPlaceholder(ir_context, *inst_to_info.first)) {
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// Check the fresh ids.
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for (uint32_t id : {inst_to_info.second.actual_result_id(),
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inst_to_info.second.alternative_block_id(),
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inst_to_info.second.placeholder_result_id()}) {
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if (!id || !CheckIdIsFreshAndNotUsedByThisTransformation(
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id, ir_context, &used_fresh_ids)) {
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return false;
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}
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}
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// Check that the placeholder value id exists, has the right type and is
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// available to use at this point.
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auto value_def = ir_context->get_def_use_mgr()->GetDef(
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inst_to_info.second.value_to_copy_id());
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if (!value_def ||
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value_def->type_id() != inst_to_info.first->type_id() ||
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!fuzzerutil::IdIsAvailableBeforeInstruction(
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ir_context, inst_to_info.first,
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inst_to_info.second.value_to_copy_id())) {
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return false;
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}
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}
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}
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}
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// If some instructions that require ids are not in the map, the
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// transformation needs overflow ids to be applicable.
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for (auto instruction : instructions_that_need_ids) {
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if (insts_to_wrapper_info.count(instruction) == 0 &&
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!transformation_context.GetOverflowIdSource()->HasOverflowIds()) {
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return false;
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}
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}
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if (OpSelectArgumentsAreRestricted(ir_context)) {
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// OpPhi instructions at the convergence block for the selection are handled
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// by turning them into OpSelect instructions. As the SPIR-V version in use
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// has restrictions on the arguments that OpSelect can take, we must check
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// that any OpPhi instructions are compatible with these restrictions.
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uint32_t convergence_block_id =
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FindConvergenceBlock(ir_context, *header_block);
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// Consider every OpPhi instruction at the convergence block.
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if (!ir_context->cfg()
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->block(convergence_block_id)
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->WhileEachPhiInst([this,
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ir_context](opt::Instruction* inst) -> bool {
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// Decide whether the OpPhi can be handled based on its result
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// type.
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opt::Instruction* phi_result_type =
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ir_context->get_def_use_mgr()->GetDef(inst->type_id());
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switch (phi_result_type->opcode()) {
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case spv::Op::OpTypeBool:
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case spv::Op::OpTypeInt:
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case spv::Op::OpTypeFloat:
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case spv::Op::OpTypePointer:
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// Fine: OpSelect can work directly on scalar and pointer
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// types.
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return true;
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case spv::Op::OpTypeVector: {
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// In its restricted form, OpSelect can only select between
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// vectors if the condition of the select is a boolean
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// boolean vector. We thus require the appropriate boolean
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// vector type to be present.
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uint32_t bool_type_id =
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fuzzerutil::MaybeGetBoolType(ir_context);
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if (!bool_type_id) {
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return false;
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}
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uint32_t dimension =
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phi_result_type->GetSingleWordInOperand(1);
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if (fuzzerutil::MaybeGetVectorType(ir_context, bool_type_id,
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dimension) == 0) {
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// The required boolean vector type is not present.
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return false;
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}
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// The transformation needs to be equipped with a fresh id
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// in which to store the vectorized version of the selection
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// construct's condition.
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switch (dimension) {
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case 2:
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return message_.fresh_id_for_bvec2_selector() != 0;
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case 3:
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return message_.fresh_id_for_bvec3_selector() != 0;
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default:
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assert(dimension == 4 && "Invalid vector dimension.");
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return message_.fresh_id_for_bvec4_selector() != 0;
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}
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}
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default:
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return false;
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}
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})) {
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return false;
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}
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}
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// All checks were passed.
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return true;
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}
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void TransformationFlattenConditionalBranch::Apply(
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opt::IRContext* ir_context,
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TransformationContext* transformation_context) const {
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// branch = 1 corresponds to the true branch, branch = 2 corresponds to the
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// false branch. If the true branch is to be laid out first, we need to visit
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// the false branch first, because each branch is moved to right after the
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// header while it is visited.
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std::vector<uint32_t> branches = {2, 1};
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if (!message_.true_branch_first()) {
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// Similarly, we need to visit the true branch first, if we want it to be
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// laid out after the false branch.
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branches = {1, 2};
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}
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auto header_block = ir_context->cfg()->block(message_.header_block_id());
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// Get the ids of the starting blocks of the first and last branches to be
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// laid out. The first branch is the true branch iff
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// |message_.true_branch_first| is true.
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auto branch_instruction = header_block->terminator();
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uint32_t first_block_first_branch_id =
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branch_instruction->GetSingleWordInOperand(branches[1]);
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uint32_t first_block_last_branch_id =
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branch_instruction->GetSingleWordInOperand(branches[0]);
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uint32_t convergence_block_id =
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FindConvergenceBlock(ir_context, *header_block);
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// If the OpBranchConditional instruction in the header branches to the same
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// block for both values of the condition, this is the convergence block (the
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// flow does not actually diverge) and the OpPhi instructions in it are still
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// valid, so we do not need to make any changes.
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if (first_block_first_branch_id != first_block_last_branch_id) {
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RewriteOpPhiInstructionsAtConvergenceBlock(
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*header_block, convergence_block_id, ir_context);
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}
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// Get the mapping from instructions to fresh ids.
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auto insts_to_info = GetInstructionsToWrapperInfo(ir_context);
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// Get a reference to the last block in the first branch that will be laid out
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// (this depends on |message_.true_branch_first|). The last block is the block
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// in the branch just before flow converges (it might not exist).
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opt::BasicBlock* last_block_first_branch = nullptr;
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// Keep track of blocks and ids for which we should later add dead block and
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// irrelevant id facts. We wait until we have finished applying the
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// transformation before adding these facts, so that the fact manager has
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// access to the fully up-to-date module.
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std::vector<uint32_t> dead_blocks;
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std::vector<uint32_t> irrelevant_ids;
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// Adjust the conditional branches by enclosing problematic instructions
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// within conditionals and get references to the last block in each branch.
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for (uint32_t branch : branches) {
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auto current_block = header_block;
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// Get the id of the first block in this branch.
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uint32_t next_block_id = branch_instruction->GetSingleWordInOperand(branch);
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// Consider all blocks in the branch until the convergence block is reached.
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while (next_block_id != convergence_block_id) {
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// Move the next block to right after the current one.
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current_block->GetParent()->MoveBasicBlockToAfter(next_block_id,
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current_block);
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// Move forward in the branch.
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current_block = ir_context->cfg()->block(next_block_id);
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// Find all the instructions in the current block which need to be
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// enclosed inside conditionals.
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std::vector<opt::Instruction*> problematic_instructions;
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current_block->ForEachInst(
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[&problematic_instructions](opt::Instruction* instruction) {
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if (instruction->opcode() != spv::Op::OpLabel &&
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instruction->opcode() != spv::Op::OpBranch &&
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!fuzzerutil::InstructionHasNoSideEffects(*instruction)) {
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problematic_instructions.push_back(instruction);
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}
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});
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uint32_t condition_id =
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header_block->terminator()->GetSingleWordInOperand(0);
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// Enclose all of the problematic instructions in conditionals, with the
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// same condition as the selection construct being flattened.
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for (auto instruction : problematic_instructions) {
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// Get the info needed by this instruction to wrap it inside a
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// conditional.
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protobufs::SideEffectWrapperInfo wrapper_info;
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if (insts_to_info.count(instruction) != 0) {
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// Get the fresh ids from the map, if present.
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wrapper_info = insts_to_info[instruction];
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} else {
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// If we could not get it from the map, use overflow ids. We don't
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// need to set |wrapper_info.instruction|, as it will not be used.
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wrapper_info.set_merge_block_id(
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transformation_context->GetOverflowIdSource()
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->GetNextOverflowId());
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wrapper_info.set_execute_block_id(
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transformation_context->GetOverflowIdSource()
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->GetNextOverflowId());
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if (InstructionNeedsPlaceholder(ir_context, *instruction)) {
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// Ge the fresh ids from the overflow ids.
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wrapper_info.set_actual_result_id(
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transformation_context->GetOverflowIdSource()
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->GetNextOverflowId());
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wrapper_info.set_alternative_block_id(
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transformation_context->GetOverflowIdSource()
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->GetNextOverflowId());
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wrapper_info.set_placeholder_result_id(
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transformation_context->GetOverflowIdSource()
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->GetNextOverflowId());
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// Try to find a zero constant. It does not matter whether it is
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// relevant or irrelevant.
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for (bool is_irrelevant : {true, false}) {
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wrapper_info.set_value_to_copy_id(
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fuzzerutil::MaybeGetZeroConstant(
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ir_context, *transformation_context,
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instruction->type_id(), is_irrelevant));
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if (wrapper_info.value_to_copy_id()) {
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break;
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}
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}
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}
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}
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// Enclose the instruction in a conditional and get the merge block
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// generated by this operation (this is where all the following
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// instructions will be).
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current_block = EncloseInstructionInConditional(
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ir_context, *transformation_context, current_block, instruction,
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wrapper_info, condition_id, branch == 1, &dead_blocks,
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&irrelevant_ids);
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}
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next_block_id = current_block->terminator()->GetSingleWordInOperand(0);
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// If the next block is the convergence block and this the branch that
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// will be laid out right after the header, record this as the last block
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// in the first branch.
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if (next_block_id == convergence_block_id && branch == branches[1]) {
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last_block_first_branch = current_block;
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}
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}
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}
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// The current header should unconditionally branch to the starting block in
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// the first branch to be laid out, if such a branch exists (i.e. the header
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// does not branch directly to the convergence block), and to the starting
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// block in the last branch to be laid out otherwise.
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uint32_t after_header = first_block_first_branch_id != convergence_block_id
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? first_block_first_branch_id
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: first_block_last_branch_id;
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// Kill the merge instruction and the branch instruction in the current
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// header.
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auto merge_inst = header_block->GetMergeInst();
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ir_context->KillInst(branch_instruction);
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ir_context->KillInst(merge_inst);
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// Add a new, unconditional, branch instruction from the current header to
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// |after_header|.
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header_block->AddInstruction(MakeUnique<opt::Instruction>(
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ir_context, spv::Op::OpBranch, 0, 0,
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opt::Instruction::OperandList{{SPV_OPERAND_TYPE_ID, {after_header}}}));
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// If the first branch to be laid out exists, change the branch instruction so
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// that the last block in such branch unconditionally branches to the first
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// block in the other branch (or the convergence block if there is no other
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// branch) and change the OpPhi instructions in the last branch accordingly
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// (the predecessor changed).
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if (last_block_first_branch) {
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last_block_first_branch->terminator()->SetInOperand(
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0, {first_block_last_branch_id});
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// Change the OpPhi instructions of the last branch (if there is another
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// branch) so that the predecessor is now the last block of the first
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// branch. The block must have a single predecessor, so the operand
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// specifying the predecessor is always in the same position.
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if (first_block_last_branch_id != convergence_block_id) {
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ir_context->get_instr_block(first_block_last_branch_id)
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->ForEachPhiInst(
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[&last_block_first_branch](opt::Instruction* phi_inst) {
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// The operand specifying the predecessor is the second input
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// operand.
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phi_inst->SetInOperand(1, {last_block_first_branch->id()});
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});
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}
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}
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// Invalidate all analyses
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ir_context->InvalidateAnalysesExceptFor(opt::IRContext::kAnalysisNone);
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// Now that we have finished adding blocks and ids to the module and
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// invalidated existing analyses, update the fact manager regarding dead
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// blocks and irrelevant ids.
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for (auto dead_block : dead_blocks) {
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transformation_context->GetFactManager()->AddFactBlockIsDead(dead_block);
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}
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for (auto irrelevant_id : irrelevant_ids) {
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transformation_context->GetFactManager()->AddFactIdIsIrrelevant(
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irrelevant_id);
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}
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}
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protobufs::Transformation TransformationFlattenConditionalBranch::ToMessage()
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const {
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protobufs::Transformation result;
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*result.mutable_flatten_conditional_branch() = message_;
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return result;
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}
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bool TransformationFlattenConditionalBranch::
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GetProblematicInstructionsIfConditionalCanBeFlattened(
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opt::IRContext* ir_context, opt::BasicBlock* header,
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const TransformationContext& transformation_context,
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std::set<opt::Instruction*>* instructions_that_need_ids) {
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uint32_t merge_block_id = header->MergeBlockIdIfAny();
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assert(merge_block_id &&
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header->GetMergeInst()->opcode() == spv::Op::OpSelectionMerge &&
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header->terminator()->opcode() == spv::Op::OpBranchConditional &&
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"|header| must be the header of a conditional.");
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// |header| must be reachable.
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if (!ir_context->IsReachable(*header)) {
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return false;
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}
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auto enclosing_function = header->GetParent();
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auto dominator_analysis =
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ir_context->GetDominatorAnalysis(enclosing_function);
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auto postdominator_analysis =
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ir_context->GetPostDominatorAnalysis(enclosing_function);
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// Check that the header and the merge block describe a single-entry,
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// single-exit region.
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if (!dominator_analysis->Dominates(header->id(), merge_block_id) ||
|
|
!postdominator_analysis->Dominates(merge_block_id, header->id())) {
|
|
return false;
|
|
}
|
|
|
|
// Traverse the CFG starting from the header and check that, for all the
|
|
// blocks that can be reached by the header before the flow converges:
|
|
// - they don't contain merge, barrier or OpSampledImage instructions
|
|
// - they branch unconditionally to another block
|
|
// Add any side-effecting instruction, requiring fresh ids, to
|
|
// |instructions_that_need_ids|
|
|
std::queue<uint32_t> to_check;
|
|
header->ForEachSuccessorLabel(
|
|
[&to_check](uint32_t label) { to_check.push(label); });
|
|
|
|
auto* structured_cfg = ir_context->GetStructuredCFGAnalysis();
|
|
while (!to_check.empty()) {
|
|
uint32_t block_id = to_check.front();
|
|
to_check.pop();
|
|
|
|
if (structured_cfg->ContainingConstruct(block_id) != header->id() &&
|
|
block_id != merge_block_id) {
|
|
// This block can be reached from the |header| but doesn't belong to its
|
|
// selection construct. This might be a continue target of some loop -
|
|
// we can't flatten the |header|.
|
|
return false;
|
|
}
|
|
|
|
// If the block post-dominates the header, this is where flow converges, and
|
|
// we don't need to check this branch any further, because the
|
|
// transformation will only change the part of the graph where flow is
|
|
// divergent.
|
|
if (postdominator_analysis->Dominates(block_id, header->id())) {
|
|
continue;
|
|
}
|
|
|
|
if (!transformation_context.GetFactManager()->BlockIsDead(header->id()) &&
|
|
transformation_context.GetFactManager()->BlockIsDead(block_id)) {
|
|
// The |header| is not dead but the |block_id| is. Since |block_id|
|
|
// doesn't postdominate the |header|, CFG hasn't converged yet. Thus, we
|
|
// don't flatten the construct to prevent |block_id| from becoming
|
|
// executable.
|
|
return false;
|
|
}
|
|
|
|
auto block = ir_context->cfg()->block(block_id);
|
|
|
|
// The block must not have a merge instruction, because inner constructs are
|
|
// not allowed.
|
|
if (block->GetMergeInst()) {
|
|
return false;
|
|
}
|
|
|
|
// The terminator instruction for the block must be OpBranch.
|
|
if (block->terminator()->opcode() != spv::Op::OpBranch) {
|
|
return false;
|
|
}
|
|
|
|
// The base objects for all data descriptors involved in synonym facts.
|
|
std::unordered_set<uint32_t> synonym_base_objects;
|
|
for (auto* synonym :
|
|
transformation_context.GetFactManager()->GetAllSynonyms()) {
|
|
synonym_base_objects.insert(synonym->object());
|
|
}
|
|
|
|
// Check all of the instructions in the block.
|
|
bool all_instructions_compatible = block->WhileEachInst(
|
|
[ir_context, instructions_that_need_ids,
|
|
&synonym_base_objects](opt::Instruction* instruction) {
|
|
// We can ignore OpLabel instructions.
|
|
if (instruction->opcode() == spv::Op::OpLabel) {
|
|
return true;
|
|
}
|
|
|
|
// If the instruction is the base object of some synonym then we
|
|
// conservatively bail out: if a synonym ends up depending on an
|
|
// instruction that needs to be enclosed in a side-effect wrapper then
|
|
// it might no longer hold after we flatten the conditional.
|
|
if (instruction->result_id() &&
|
|
synonym_base_objects.count(instruction->result_id())) {
|
|
return false;
|
|
}
|
|
|
|
// If the instruction is a branch, it must be an unconditional branch.
|
|
if (instruction->IsBranch()) {
|
|
return instruction->opcode() == spv::Op::OpBranch;
|
|
}
|
|
|
|
// We cannot go ahead if we encounter an instruction that cannot be
|
|
// handled.
|
|
if (!InstructionCanBeHandled(ir_context, *instruction)) {
|
|
return false;
|
|
}
|
|
|
|
// If the instruction has side effects, add it to the
|
|
// |instructions_that_need_ids| set.
|
|
if (!fuzzerutil::InstructionHasNoSideEffects(*instruction)) {
|
|
instructions_that_need_ids->emplace(instruction);
|
|
}
|
|
|
|
return true;
|
|
});
|
|
|
|
if (!all_instructions_compatible) {
|
|
return false;
|
|
}
|
|
|
|
// Add the successor of this block to the list of blocks that need to be
|
|
// checked.
|
|
to_check.push(block->terminator()->GetSingleWordInOperand(0));
|
|
}
|
|
|
|
// All the blocks are compatible with the transformation and this is indeed a
|
|
// single-entry, single-exit region.
|
|
return true;
|
|
}
|
|
|
|
bool TransformationFlattenConditionalBranch::InstructionNeedsPlaceholder(
|
|
opt::IRContext* ir_context, const opt::Instruction& instruction) {
|
|
assert(!fuzzerutil::InstructionHasNoSideEffects(instruction) &&
|
|
InstructionCanBeHandled(ir_context, instruction) &&
|
|
"The instruction must have side effects and it must be possible to "
|
|
"enclose it inside a conditional.");
|
|
|
|
if (instruction.HasResultId()) {
|
|
// We need a placeholder iff the type is not Void.
|
|
auto type = ir_context->get_type_mgr()->GetType(instruction.type_id());
|
|
return type && !type->AsVoid();
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
std::unordered_map<opt::Instruction*, protobufs::SideEffectWrapperInfo>
|
|
TransformationFlattenConditionalBranch::GetInstructionsToWrapperInfo(
|
|
opt::IRContext* ir_context) const {
|
|
std::unordered_map<opt::Instruction*, protobufs::SideEffectWrapperInfo>
|
|
instructions_to_ids;
|
|
for (const auto& wrapper_info : message_.side_effect_wrapper_info()) {
|
|
auto instruction = FindInstruction(wrapper_info.instruction(), ir_context);
|
|
if (instruction) {
|
|
instructions_to_ids.emplace(instruction, wrapper_info);
|
|
}
|
|
}
|
|
|
|
return instructions_to_ids;
|
|
}
|
|
|
|
opt::BasicBlock*
|
|
TransformationFlattenConditionalBranch::EncloseInstructionInConditional(
|
|
opt::IRContext* ir_context,
|
|
const TransformationContext& transformation_context, opt::BasicBlock* block,
|
|
opt::Instruction* instruction,
|
|
const protobufs::SideEffectWrapperInfo& wrapper_info, uint32_t condition_id,
|
|
bool exec_if_cond_true, std::vector<uint32_t>* dead_blocks,
|
|
std::vector<uint32_t>* irrelevant_ids) {
|
|
// Get the next instruction (it will be useful for splitting).
|
|
auto next_instruction = instruction->NextNode();
|
|
|
|
// Update the module id bound.
|
|
for (uint32_t id :
|
|
{wrapper_info.merge_block_id(), wrapper_info.execute_block_id()}) {
|
|
fuzzerutil::UpdateModuleIdBound(ir_context, id);
|
|
}
|
|
|
|
// Create the block where the instruction is executed by splitting the
|
|
// original block.
|
|
auto execute_block = block->SplitBasicBlock(
|
|
ir_context, wrapper_info.execute_block_id(),
|
|
fuzzerutil::GetIteratorForInstruction(block, instruction));
|
|
|
|
// Create the merge block for the conditional that we are about to create by
|
|
// splitting execute_block (this will leave |instruction| as the only
|
|
// instruction in |execute_block|).
|
|
auto merge_block = execute_block->SplitBasicBlock(
|
|
ir_context, wrapper_info.merge_block_id(),
|
|
fuzzerutil::GetIteratorForInstruction(execute_block, next_instruction));
|
|
|
|
// Propagate the fact that the block is dead to the newly-created blocks.
|
|
if (transformation_context.GetFactManager()->BlockIsDead(block->id())) {
|
|
dead_blocks->emplace_back(execute_block->id());
|
|
dead_blocks->emplace_back(merge_block->id());
|
|
}
|
|
|
|
// Initially, consider the merge block as the alternative block to branch to
|
|
// if the instruction should not be executed.
|
|
auto alternative_block = merge_block;
|
|
|
|
// Add an unconditional branch from |execute_block| to |merge_block|.
|
|
execute_block->AddInstruction(MakeUnique<opt::Instruction>(
|
|
ir_context, spv::Op::OpBranch, 0, 0,
|
|
opt::Instruction::OperandList{
|
|
{SPV_OPERAND_TYPE_ID, {merge_block->id()}}}));
|
|
|
|
// If the instruction requires a placeholder, it means that it has a result id
|
|
// and its result needs to be able to be used later on, and we need to:
|
|
// - add an additional block |ids.alternative_block_id| where a placeholder
|
|
// result id (using fresh id |ids.placeholder_result_id|) is obtained either
|
|
// by using OpCopyObject and copying |ids.value_to_copy_id| or, if such id
|
|
// was not given and a suitable constant was not found, by using OpUndef.
|
|
// - mark |ids.placeholder_result_id| as irrelevant
|
|
// - change the result id of the instruction to a fresh id
|
|
// (|ids.actual_result_id|).
|
|
// - add an OpPhi instruction, which will have the original result id of the
|
|
// instruction, in the merge block.
|
|
if (InstructionNeedsPlaceholder(ir_context, *instruction)) {
|
|
// Update the module id bound with the additional ids.
|
|
for (uint32_t id :
|
|
{wrapper_info.actual_result_id(), wrapper_info.alternative_block_id(),
|
|
wrapper_info.placeholder_result_id()}) {
|
|
fuzzerutil::UpdateModuleIdBound(ir_context, id);
|
|
}
|
|
|
|
// Create a new block using |fresh_ids.alternative_block_id| for its label.
|
|
auto alternative_block_temp = MakeUnique<opt::BasicBlock>(
|
|
MakeUnique<opt::Instruction>(ir_context, spv::Op::OpLabel, 0,
|
|
wrapper_info.alternative_block_id(),
|
|
opt::Instruction::OperandList{}));
|
|
|
|
// Keep the original result id of the instruction in a variable.
|
|
uint32_t original_result_id = instruction->result_id();
|
|
|
|
// Set the result id of the instruction to be |ids.actual_result_id|.
|
|
instruction->SetResultId(wrapper_info.actual_result_id());
|
|
|
|
// Add a placeholder instruction, with the same type as the original
|
|
// instruction and id |ids.placeholder_result_id|, to the new block.
|
|
if (wrapper_info.value_to_copy_id()) {
|
|
// If there is an available id to copy from, the placeholder instruction
|
|
// will be %placeholder_result_id = OpCopyObject %type %value_to_copy_id
|
|
alternative_block_temp->AddInstruction(MakeUnique<opt::Instruction>(
|
|
ir_context, spv::Op::OpCopyObject, instruction->type_id(),
|
|
wrapper_info.placeholder_result_id(),
|
|
opt::Instruction::OperandList{
|
|
{SPV_OPERAND_TYPE_ID, {wrapper_info.value_to_copy_id()}}}));
|
|
} else {
|
|
// If there is no such id, use an OpUndef instruction.
|
|
alternative_block_temp->AddInstruction(MakeUnique<opt::Instruction>(
|
|
ir_context, spv::Op::OpUndef, instruction->type_id(),
|
|
wrapper_info.placeholder_result_id(),
|
|
opt::Instruction::OperandList{}));
|
|
}
|
|
|
|
// Mark |ids.placeholder_result_id| as irrelevant.
|
|
irrelevant_ids->emplace_back(wrapper_info.placeholder_result_id());
|
|
|
|
// Add an unconditional branch from the new block to the merge block.
|
|
alternative_block_temp->AddInstruction(MakeUnique<opt::Instruction>(
|
|
ir_context, spv::Op::OpBranch, 0, 0,
|
|
opt::Instruction::OperandList{
|
|
{SPV_OPERAND_TYPE_ID, {merge_block->id()}}}));
|
|
|
|
// Insert the block before the merge block.
|
|
alternative_block = block->GetParent()->InsertBasicBlockBefore(
|
|
std::move(alternative_block_temp), merge_block);
|
|
|
|
// Using the original instruction result id, add an OpPhi instruction to the
|
|
// merge block, which will either take the value of the result of the
|
|
// instruction or the placeholder value defined in the alternative block.
|
|
merge_block->begin().InsertBefore(MakeUnique<opt::Instruction>(
|
|
ir_context, spv::Op::OpPhi, instruction->type_id(), original_result_id,
|
|
opt::Instruction::OperandList{
|
|
{SPV_OPERAND_TYPE_ID, {instruction->result_id()}},
|
|
{SPV_OPERAND_TYPE_ID, {execute_block->id()}},
|
|
{SPV_OPERAND_TYPE_ID, {wrapper_info.placeholder_result_id()}},
|
|
{SPV_OPERAND_TYPE_ID, {alternative_block->id()}}}));
|
|
|
|
// Propagate the fact that the block is dead to the new block.
|
|
if (transformation_context.GetFactManager()->BlockIsDead(block->id())) {
|
|
dead_blocks->emplace_back(alternative_block->id());
|
|
}
|
|
}
|
|
|
|
// Depending on whether the instruction should be executed in the if branch or
|
|
// in the else branch, get the corresponding ids.
|
|
auto if_block_id = (exec_if_cond_true ? execute_block : alternative_block)
|
|
->GetLabel()
|
|
->result_id();
|
|
auto else_block_id = (exec_if_cond_true ? alternative_block : execute_block)
|
|
->GetLabel()
|
|
->result_id();
|
|
|
|
// Add an OpSelectionMerge instruction to the block.
|
|
block->AddInstruction(MakeUnique<opt::Instruction>(
|
|
ir_context, spv::Op::OpSelectionMerge, 0, 0,
|
|
opt::Instruction::OperandList{
|
|
{SPV_OPERAND_TYPE_ID, {merge_block->id()}},
|
|
{SPV_OPERAND_TYPE_SELECTION_CONTROL,
|
|
{uint32_t(spv::SelectionControlMask::MaskNone)}}}));
|
|
|
|
// Add an OpBranchConditional, to the block, using |condition_id| as the
|
|
// condition and branching to |if_block_id| if the condition is true and to
|
|
// |else_block_id| if the condition is false.
|
|
block->AddInstruction(MakeUnique<opt::Instruction>(
|
|
ir_context, spv::Op::OpBranchConditional, 0, 0,
|
|
opt::Instruction::OperandList{{SPV_OPERAND_TYPE_ID, {condition_id}},
|
|
{SPV_OPERAND_TYPE_ID, {if_block_id}},
|
|
{SPV_OPERAND_TYPE_ID, {else_block_id}}}));
|
|
|
|
return merge_block;
|
|
}
|
|
|
|
bool TransformationFlattenConditionalBranch::InstructionCanBeHandled(
|
|
opt::IRContext* ir_context, const opt::Instruction& instruction) {
|
|
// We can handle all instructions with no side effects.
|
|
if (fuzzerutil::InstructionHasNoSideEffects(instruction)) {
|
|
return true;
|
|
}
|
|
|
|
// We cannot handle barrier instructions, while we should be able to handle
|
|
// all other instructions by enclosing them inside a conditional.
|
|
if (instruction.opcode() == spv::Op::OpControlBarrier ||
|
|
instruction.opcode() == spv::Op::OpMemoryBarrier ||
|
|
instruction.opcode() == spv::Op::OpNamedBarrierInitialize ||
|
|
instruction.opcode() == spv::Op::OpMemoryNamedBarrier ||
|
|
instruction.opcode() == spv::Op::OpTypeNamedBarrier) {
|
|
return false;
|
|
}
|
|
|
|
// We cannot handle OpSampledImage instructions, as they need to be in the
|
|
// same block as their use.
|
|
if (instruction.opcode() == spv::Op::OpSampledImage) {
|
|
return false;
|
|
}
|
|
|
|
// We cannot handle a sampled image load, because we re-work loads using
|
|
// conditional branches and OpPhi instructions, and the result type of OpPhi
|
|
// cannot be OpTypeSampledImage.
|
|
if (instruction.opcode() == spv::Op::OpLoad &&
|
|
ir_context->get_def_use_mgr()->GetDef(instruction.type_id())->opcode() ==
|
|
spv::Op::OpTypeSampledImage) {
|
|
return false;
|
|
}
|
|
|
|
// We cannot handle instructions with an id which return a void type, if the
|
|
// result id is used in the module (e.g. a function call to a function that
|
|
// returns nothing).
|
|
if (instruction.HasResultId()) {
|
|
auto type = ir_context->get_type_mgr()->GetType(instruction.type_id());
|
|
assert(type && "The type should be found in the module");
|
|
|
|
if (type->AsVoid() &&
|
|
!ir_context->get_def_use_mgr()->WhileEachUse(
|
|
instruction.result_id(),
|
|
[](opt::Instruction* use_inst, uint32_t use_index) {
|
|
// Return false if the id is used as an input operand.
|
|
return use_index <
|
|
use_inst->NumOperands() - use_inst->NumInOperands();
|
|
})) {
|
|
return false;
|
|
}
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
std::unordered_set<uint32_t>
|
|
TransformationFlattenConditionalBranch::GetFreshIds() const {
|
|
std::unordered_set<uint32_t> result = {
|
|
message_.fresh_id_for_bvec2_selector(),
|
|
message_.fresh_id_for_bvec3_selector(),
|
|
message_.fresh_id_for_bvec4_selector()};
|
|
for (auto& side_effect_wrapper_info : message_.side_effect_wrapper_info()) {
|
|
result.insert(side_effect_wrapper_info.merge_block_id());
|
|
result.insert(side_effect_wrapper_info.execute_block_id());
|
|
result.insert(side_effect_wrapper_info.actual_result_id());
|
|
result.insert(side_effect_wrapper_info.alternative_block_id());
|
|
result.insert(side_effect_wrapper_info.placeholder_result_id());
|
|
}
|
|
return result;
|
|
}
|
|
|
|
uint32_t TransformationFlattenConditionalBranch::FindConvergenceBlock(
|
|
opt::IRContext* ir_context, const opt::BasicBlock& header_block) {
|
|
uint32_t result = header_block.terminator()->GetSingleWordInOperand(1);
|
|
auto postdominator_analysis =
|
|
ir_context->GetPostDominatorAnalysis(header_block.GetParent());
|
|
while (!postdominator_analysis->Dominates(result, header_block.id())) {
|
|
auto current_block = ir_context->get_instr_block(result);
|
|
// If the transformation is applicable, the terminator is OpBranch.
|
|
result = current_block->terminator()->GetSingleWordInOperand(0);
|
|
}
|
|
return result;
|
|
}
|
|
|
|
bool TransformationFlattenConditionalBranch::OpSelectArgumentsAreRestricted(
|
|
opt::IRContext* ir_context) {
|
|
switch (ir_context->grammar().target_env()) {
|
|
case SPV_ENV_UNIVERSAL_1_0:
|
|
case SPV_ENV_UNIVERSAL_1_1:
|
|
case SPV_ENV_UNIVERSAL_1_2:
|
|
case SPV_ENV_UNIVERSAL_1_3:
|
|
case SPV_ENV_VULKAN_1_0:
|
|
case SPV_ENV_VULKAN_1_1: {
|
|
return true;
|
|
}
|
|
default:
|
|
return false;
|
|
}
|
|
}
|
|
|
|
void TransformationFlattenConditionalBranch::AddBooleanVectorConstructorToBlock(
|
|
uint32_t fresh_id, uint32_t dimension,
|
|
const opt::Operand& branch_condition_operand, opt::IRContext* ir_context,
|
|
opt::BasicBlock* block) {
|
|
opt::Instruction::OperandList in_operands;
|
|
for (uint32_t i = 0; i < dimension; i++) {
|
|
in_operands.emplace_back(branch_condition_operand);
|
|
}
|
|
block->begin()->InsertBefore(MakeUnique<opt::Instruction>(
|
|
ir_context, spv::Op::OpCompositeConstruct,
|
|
fuzzerutil::MaybeGetVectorType(
|
|
ir_context, fuzzerutil::MaybeGetBoolType(ir_context), dimension),
|
|
fresh_id, in_operands));
|
|
fuzzerutil::UpdateModuleIdBound(ir_context, fresh_id);
|
|
}
|
|
|
|
void TransformationFlattenConditionalBranch::
|
|
RewriteOpPhiInstructionsAtConvergenceBlock(
|
|
const opt::BasicBlock& header_block, uint32_t convergence_block_id,
|
|
opt::IRContext* ir_context) const {
|
|
const opt::Instruction& branch_instruction = *header_block.terminator();
|
|
|
|
const opt::Operand& branch_condition_operand =
|
|
branch_instruction.GetInOperand(0);
|
|
|
|
// If we encounter OpPhi instructions on vector types then we may need to
|
|
// introduce vector versions of the selection construct's condition to use
|
|
// in corresponding OpSelect instructions. These booleans track whether we
|
|
// need to introduce such boolean vectors.
|
|
bool require_2d_boolean_vector = false;
|
|
bool require_3d_boolean_vector = false;
|
|
bool require_4d_boolean_vector = false;
|
|
|
|
// Consider every OpPhi instruction at the convergence block.
|
|
opt::BasicBlock* convergence_block =
|
|
ir_context->get_instr_block(convergence_block_id);
|
|
convergence_block->ForEachPhiInst(
|
|
[this, &branch_condition_operand, branch_instruction,
|
|
convergence_block_id, &header_block, ir_context,
|
|
&require_2d_boolean_vector, &require_3d_boolean_vector,
|
|
&require_4d_boolean_vector](opt::Instruction* phi_inst) {
|
|
assert(phi_inst->NumInOperands() == 4 &&
|
|
"We are going to replace an OpPhi with an OpSelect. This "
|
|
"only makes sense if the block has two distinct "
|
|
"predecessors.");
|
|
// We are going to replace the OpPhi with an OpSelect. By default,
|
|
// the condition for the OpSelect will be the branch condition's
|
|
// operand. However, if the OpPhi has vector result type we may need
|
|
// to use a boolean vector as the condition instead.
|
|
opt::Operand selector_operand = branch_condition_operand;
|
|
opt::Instruction* type_inst =
|
|
ir_context->get_def_use_mgr()->GetDef(phi_inst->type_id());
|
|
if (type_inst->opcode() == spv::Op::OpTypeVector) {
|
|
uint32_t dimension = type_inst->GetSingleWordInOperand(1);
|
|
switch (dimension) {
|
|
case 2:
|
|
// The OpPhi's result type is a 2D vector. If a fresh id for a
|
|
// bvec2 selector was provided then we should use it as the
|
|
// OpSelect's condition, and note the fact that we will need to
|
|
// add an instruction to bring this bvec2 into existence.
|
|
if (message_.fresh_id_for_bvec2_selector() != 0) {
|
|
selector_operand = {SPV_OPERAND_TYPE_ID,
|
|
{message_.fresh_id_for_bvec2_selector()}};
|
|
require_2d_boolean_vector = true;
|
|
}
|
|
break;
|
|
case 3:
|
|
// Similar to the 2D case.
|
|
if (message_.fresh_id_for_bvec3_selector() != 0) {
|
|
selector_operand = {SPV_OPERAND_TYPE_ID,
|
|
{message_.fresh_id_for_bvec3_selector()}};
|
|
require_3d_boolean_vector = true;
|
|
}
|
|
break;
|
|
case 4:
|
|
// Similar to the 2D case.
|
|
if (message_.fresh_id_for_bvec4_selector() != 0) {
|
|
selector_operand = {SPV_OPERAND_TYPE_ID,
|
|
{message_.fresh_id_for_bvec4_selector()}};
|
|
require_4d_boolean_vector = true;
|
|
}
|
|
break;
|
|
default:
|
|
assert(dimension == 4 && "Invalid vector dimension.");
|
|
break;
|
|
}
|
|
}
|
|
std::vector<opt::Operand> operands;
|
|
operands.emplace_back(selector_operand);
|
|
|
|
uint32_t branch_instruction_true_block_id =
|
|
branch_instruction.GetSingleWordInOperand(1);
|
|
uint32_t branch_instruction_false_block_id =
|
|
branch_instruction.GetSingleWordInOperand(2);
|
|
|
|
// The OpPhi takes values from two distinct predecessors. One
|
|
// predecessor is associated with the "true" path of the conditional
|
|
// we are flattening, the other with the "false" path, but these
|
|
// predecessors can appear in either order as operands to the OpPhi
|
|
// instruction. We determine in which order the OpPhi inputs should
|
|
// appear as OpSelect arguments by first checking whether the
|
|
// convergence block is a direct successor of the selection header, and
|
|
// otherwise checking dominance of the true and false immediate
|
|
// successors of the header block.
|
|
if (branch_instruction_true_block_id == convergence_block_id) {
|
|
// The branch instruction's true block is the convergence block. This
|
|
// means that the OpPhi's value associated with the branch
|
|
// instruction's block should the "true" result of the OpSelect.
|
|
assert(branch_instruction_false_block_id != convergence_block_id &&
|
|
"Control should not reach here if both branches target the "
|
|
"convergence block.");
|
|
if (phi_inst->GetSingleWordInOperand(1) ==
|
|
message_.header_block_id()) {
|
|
operands.emplace_back(phi_inst->GetInOperand(0));
|
|
operands.emplace_back(phi_inst->GetInOperand(2));
|
|
} else {
|
|
assert(phi_inst->GetSingleWordInOperand(3) ==
|
|
message_.header_block_id() &&
|
|
"Since the convergence block has the header block as one of "
|
|
"two predecessors, if it is not handled by the first pair "
|
|
"of operands of this OpPhi instruction it should be handled "
|
|
"by the second pair.");
|
|
operands.emplace_back(phi_inst->GetInOperand(2));
|
|
operands.emplace_back(phi_inst->GetInOperand(0));
|
|
}
|
|
} else if (branch_instruction_false_block_id == convergence_block_id) {
|
|
// The branch instruction's false block is the convergence block. This
|
|
// means that the OpPhi's value associated with the branch
|
|
// instruction's block should the "false" result of the OpSelect.
|
|
if (phi_inst->GetSingleWordInOperand(1) ==
|
|
message_.header_block_id()) {
|
|
operands.emplace_back(phi_inst->GetInOperand(2));
|
|
operands.emplace_back(phi_inst->GetInOperand(0));
|
|
} else {
|
|
assert(phi_inst->GetSingleWordInOperand(3) ==
|
|
message_.header_block_id() &&
|
|
"Since the convergence block has the header block as one of "
|
|
"two predecessors, if it is not handled by the first pair "
|
|
"of operands of this OpPhi instruction it should be handled "
|
|
"by the second pair.");
|
|
operands.emplace_back(phi_inst->GetInOperand(0));
|
|
operands.emplace_back(phi_inst->GetInOperand(2));
|
|
}
|
|
} else if (ir_context->GetDominatorAnalysis(header_block.GetParent())
|
|
->Dominates(branch_instruction_true_block_id,
|
|
phi_inst->GetSingleWordInOperand(1))) {
|
|
// The "true" branch of the conditional is handled first in the
|
|
// OpPhi's operands; we thus provide operands to OpSelect in the same
|
|
// order that they appear in the OpPhi.
|
|
operands.emplace_back(phi_inst->GetInOperand(0));
|
|
operands.emplace_back(phi_inst->GetInOperand(2));
|
|
} else {
|
|
// The "false" branch of the conditional is handled first in the
|
|
// OpPhi's operands; we thus provide operands to OpSelect in reverse
|
|
// of the order that they appear in the OpPhi.
|
|
operands.emplace_back(phi_inst->GetInOperand(2));
|
|
operands.emplace_back(phi_inst->GetInOperand(0));
|
|
}
|
|
phi_inst->SetOpcode(spv::Op::OpSelect);
|
|
phi_inst->SetInOperands(std::move(operands));
|
|
});
|
|
|
|
// Add boolean vector instructions to the start of the block as required.
|
|
if (require_2d_boolean_vector) {
|
|
AddBooleanVectorConstructorToBlock(message_.fresh_id_for_bvec2_selector(),
|
|
2, branch_condition_operand, ir_context,
|
|
convergence_block);
|
|
}
|
|
if (require_3d_boolean_vector) {
|
|
AddBooleanVectorConstructorToBlock(message_.fresh_id_for_bvec3_selector(),
|
|
3, branch_condition_operand, ir_context,
|
|
convergence_block);
|
|
}
|
|
if (require_4d_boolean_vector) {
|
|
AddBooleanVectorConstructorToBlock(message_.fresh_id_for_bvec4_selector(),
|
|
4, branch_condition_operand, ir_context,
|
|
convergence_block);
|
|
}
|
|
}
|
|
|
|
} // namespace fuzz
|
|
} // namespace spvtools
|