SPIRV-Tools/source/fuzz/transformation_access_chain.cpp
Alastair Donaldson d0c73fcee1
spirv-fuzz: Optimize transformations (#4216)
Avoids blanket invalidation of analyses in several transformations,
instead updating the def-use manager and instruction to block mapping.
2021-03-26 10:22:06 +00:00

435 lines
17 KiB
C++

// Copyright (c) 2020 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include "source/fuzz/transformation_access_chain.h"
#include <vector>
#include "source/fuzz/fuzzer_util.h"
#include "source/fuzz/instruction_descriptor.h"
namespace spvtools {
namespace fuzz {
TransformationAccessChain::TransformationAccessChain(
protobufs::TransformationAccessChain message)
: message_(std::move(message)) {}
TransformationAccessChain::TransformationAccessChain(
uint32_t fresh_id, uint32_t pointer_id,
const std::vector<uint32_t>& index_id,
const protobufs::InstructionDescriptor& instruction_to_insert_before,
const std::vector<std::pair<uint32_t, uint32_t>>& fresh_ids_for_clamping) {
message_.set_fresh_id(fresh_id);
message_.set_pointer_id(pointer_id);
for (auto id : index_id) {
message_.add_index_id(id);
}
*message_.mutable_instruction_to_insert_before() =
instruction_to_insert_before;
for (auto clamping_ids_pair : fresh_ids_for_clamping) {
protobufs::UInt32Pair pair;
pair.set_first(clamping_ids_pair.first);
pair.set_second(clamping_ids_pair.second);
*message_.add_fresh_ids_for_clamping() = pair;
}
}
bool TransformationAccessChain::IsApplicable(
opt::IRContext* ir_context, const TransformationContext& /*unused*/) const {
// Keep track of the fresh ids used to make sure that they are distinct.
std::set<uint32_t> fresh_ids_used;
// The result id must be fresh.
if (!CheckIdIsFreshAndNotUsedByThisTransformation(
message_.fresh_id(), ir_context, &fresh_ids_used)) {
return false;
}
// The pointer id must exist and have a type.
auto pointer = ir_context->get_def_use_mgr()->GetDef(message_.pointer_id());
if (!pointer || !pointer->type_id()) {
return false;
}
// The type must indeed be a pointer.
auto pointer_type = ir_context->get_def_use_mgr()->GetDef(pointer->type_id());
if (pointer_type->opcode() != SpvOpTypePointer) {
return false;
}
// The described instruction to insert before must exist and be a suitable
// point where an OpAccessChain instruction could be inserted.
auto instruction_to_insert_before =
FindInstruction(message_.instruction_to_insert_before(), ir_context);
if (!instruction_to_insert_before) {
return false;
}
if (!fuzzerutil::CanInsertOpcodeBeforeInstruction(
SpvOpAccessChain, instruction_to_insert_before)) {
return false;
}
// Do not allow making an access chain from a null or undefined pointer, as
// we do not want to allow accessing such pointers. This might be acceptable
// in dead blocks, but we conservatively avoid it.
switch (pointer->opcode()) {
case SpvOpConstantNull:
case SpvOpUndef:
assert(
false &&
"Access chains should not be created from null/undefined pointers");
return false;
default:
break;
}
// The pointer on which the access chain is to be based needs to be available
// (according to dominance rules) at the insertion point.
if (!fuzzerutil::IdIsAvailableBeforeInstruction(
ir_context, instruction_to_insert_before, message_.pointer_id())) {
return false;
}
// We now need to use the given indices to walk the type structure of the
// base type of the pointer, making sure that (a) the indices correspond to
// integers, and (b) these integer values are in-bounds.
// Start from the base type of the pointer.
uint32_t subobject_type_id = pointer_type->GetSingleWordInOperand(1);
int id_pairs_used = 0;
// Consider the given index ids in turn.
for (auto index_id : message_.index_id()) {
// The index value will correspond to the value of the index if the object
// is a struct, otherwise the value 0 will be used.
uint32_t index_value;
// Check whether the object is a struct.
if (ir_context->get_def_use_mgr()->GetDef(subobject_type_id)->opcode() ==
SpvOpTypeStruct) {
// It is a struct: we need to retrieve the integer value.
bool successful;
std::tie(successful, index_value) =
GetIndexValue(ir_context, index_id, subobject_type_id);
if (!successful) {
return false;
}
} else {
// It is not a struct: the index will need clamping.
if (message_.fresh_ids_for_clamping().size() <= id_pairs_used) {
// We don't have enough ids
return false;
}
// Get two new ids to use and update the amount used.
protobufs::UInt32Pair fresh_ids =
message_.fresh_ids_for_clamping()[id_pairs_used++];
// Valid ids need to have been given
if (fresh_ids.first() == 0 || fresh_ids.second() == 0) {
return false;
}
// Check that the ids are actually fresh and not already used by this
// transformation.
if (!CheckIdIsFreshAndNotUsedByThisTransformation(
fresh_ids.first(), ir_context, &fresh_ids_used) ||
!CheckIdIsFreshAndNotUsedByThisTransformation(
fresh_ids.second(), ir_context, &fresh_ids_used)) {
return false;
}
if (!ValidIndexToComposite(ir_context, index_id, subobject_type_id)) {
return false;
}
// Perform the clamping using the fresh ids at our disposal.
auto index_instruction = ir_context->get_def_use_mgr()->GetDef(index_id);
uint32_t bound = fuzzerutil::GetBoundForCompositeIndex(
*ir_context->get_def_use_mgr()->GetDef(subobject_type_id),
ir_context);
// The module must have an integer constant of value bound-1 of the same
// type as the index.
if (!fuzzerutil::MaybeGetIntegerConstantFromValueAndType(
ir_context, bound - 1, index_instruction->type_id())) {
return false;
}
// The module must have the definition of bool type to make a comparison.
if (!fuzzerutil::MaybeGetBoolType(ir_context)) {
return false;
}
// The index is not necessarily a constant, so we may not know its value.
// We can use index 0 because the components of a non-struct composite
// all have the same type, and index 0 is always in bounds.
index_value = 0;
}
// Try to walk down the type using this index. This will yield 0 if the
// type is not a composite or the index is out of bounds, and the id of
// the next type otherwise.
subobject_type_id = fuzzerutil::WalkOneCompositeTypeIndex(
ir_context, subobject_type_id, index_value);
if (!subobject_type_id) {
// Either the type was not a composite (so that too many indices were
// provided), or the index was out of bounds.
return false;
}
}
// At this point, |subobject_type_id| is the type of the value targeted by
// the new access chain. The result type of the access chain should be a
// pointer to this type, with the same storage class as for the original
// pointer. Such a pointer type needs to exist in the module.
//
// We do not use the type manager to look up this type, due to problems
// associated with pointers to isomorphic structs being regarded as the same.
return fuzzerutil::MaybeGetPointerType(
ir_context, subobject_type_id,
static_cast<SpvStorageClass>(
pointer_type->GetSingleWordInOperand(0))) != 0;
}
void TransformationAccessChain::Apply(
opt::IRContext* ir_context,
TransformationContext* transformation_context) const {
// The operands to the access chain are the pointer followed by the indices.
// The result type of the access chain is determined by where the indices
// lead. We thus push the pointer to a sequence of operands, and then follow
// the indices, pushing each to the operand list and tracking the type
// obtained by following it. Ultimately this yields the type of the
// component reached by following all the indices, and the result type is
// a pointer to this component type.
opt::Instruction::OperandList operands;
// Add the pointer id itself.
operands.push_back({SPV_OPERAND_TYPE_ID, {message_.pointer_id()}});
// Start walking the indices, starting with the pointer's base type.
auto pointer_type = ir_context->get_def_use_mgr()->GetDef(
ir_context->get_def_use_mgr()->GetDef(message_.pointer_id())->type_id());
uint32_t subobject_type_id = pointer_type->GetSingleWordInOperand(1);
uint32_t id_pairs_used = 0;
opt::Instruction* instruction_to_insert_before =
FindInstruction(message_.instruction_to_insert_before(), ir_context);
opt::BasicBlock* enclosing_block =
ir_context->get_instr_block(instruction_to_insert_before);
// Go through the index ids in turn.
for (auto index_id : message_.index_id()) {
uint32_t index_value;
// Actual id to be used in the instruction: the original id
// or the clamped one.
uint32_t new_index_id;
// Check whether the object is a struct.
if (ir_context->get_def_use_mgr()->GetDef(subobject_type_id)->opcode() ==
SpvOpTypeStruct) {
// It is a struct: we need to retrieve the integer value.
index_value =
GetIndexValue(ir_context, index_id, subobject_type_id).second;
new_index_id = index_id;
} else {
// It is not a struct: the index will need clamping.
// Get two new ids to use and update the amount used.
protobufs::UInt32Pair fresh_ids =
message_.fresh_ids_for_clamping()[id_pairs_used++];
// Perform the clamping using the fresh ids at our disposal.
// The module will not be changed if |add_clamping_instructions| is not
// set.
auto index_instruction = ir_context->get_def_use_mgr()->GetDef(index_id);
uint32_t bound = fuzzerutil::GetBoundForCompositeIndex(
*ir_context->get_def_use_mgr()->GetDef(subobject_type_id),
ir_context);
auto bound_minus_one_id =
fuzzerutil::MaybeGetIntegerConstantFromValueAndType(
ir_context, bound - 1, index_instruction->type_id());
assert(bound_minus_one_id &&
"A constant of value bound - 1 and the same type as the index "
"must exist as a precondition.");
uint32_t bool_type_id = fuzzerutil::MaybeGetBoolType(ir_context);
assert(bool_type_id &&
"An OpTypeBool instruction must exist as a precondition.");
auto int_type_inst =
ir_context->get_def_use_mgr()->GetDef(index_instruction->type_id());
// Clamp the integer and add the corresponding instructions in the module
// if |add_clamping_instructions| is set.
// Compare the index with the bound via an instruction of the form:
// %fresh_ids.first = OpULessThanEqual %bool %int_id %bound_minus_one.
fuzzerutil::UpdateModuleIdBound(ir_context, fresh_ids.first());
auto comparison_instruction = MakeUnique<opt::Instruction>(
ir_context, SpvOpULessThanEqual, bool_type_id, fresh_ids.first(),
opt::Instruction::OperandList(
{{SPV_OPERAND_TYPE_ID, {index_instruction->result_id()}},
{SPV_OPERAND_TYPE_ID, {bound_minus_one_id}}}));
auto comparison_instruction_ptr = comparison_instruction.get();
instruction_to_insert_before->InsertBefore(
std::move(comparison_instruction));
ir_context->get_def_use_mgr()->AnalyzeInstDefUse(
comparison_instruction_ptr);
ir_context->set_instr_block(comparison_instruction_ptr, enclosing_block);
// Select the index if in-bounds, otherwise one less than the bound:
// %fresh_ids.second = OpSelect %int_type %fresh_ids.first %int_id
// %bound_minus_one
fuzzerutil::UpdateModuleIdBound(ir_context, fresh_ids.second());
auto select_instruction = MakeUnique<opt::Instruction>(
ir_context, SpvOpSelect, int_type_inst->result_id(),
fresh_ids.second(),
opt::Instruction::OperandList(
{{SPV_OPERAND_TYPE_ID, {fresh_ids.first()}},
{SPV_OPERAND_TYPE_ID, {index_instruction->result_id()}},
{SPV_OPERAND_TYPE_ID, {bound_minus_one_id}}}));
auto select_instruction_ptr = select_instruction.get();
instruction_to_insert_before->InsertBefore(std::move(select_instruction));
ir_context->get_def_use_mgr()->AnalyzeInstDefUse(select_instruction_ptr);
ir_context->set_instr_block(select_instruction_ptr, enclosing_block);
new_index_id = fresh_ids.second();
index_value = 0;
}
// Add the correct index id to the operands.
operands.push_back({SPV_OPERAND_TYPE_ID, {new_index_id}});
// Walk to the next type in the composite object using this index.
subobject_type_id = fuzzerutil::WalkOneCompositeTypeIndex(
ir_context, subobject_type_id, index_value);
}
// The access chain's result type is a pointer to the composite component
// that was reached after following all indices. The storage class is that
// of the original pointer.
uint32_t result_type = fuzzerutil::MaybeGetPointerType(
ir_context, subobject_type_id,
static_cast<SpvStorageClass>(pointer_type->GetSingleWordInOperand(0)));
// Add the access chain instruction to the module, and update the module's
// id bound.
fuzzerutil::UpdateModuleIdBound(ir_context, message_.fresh_id());
auto access_chain_instruction = MakeUnique<opt::Instruction>(
ir_context, SpvOpAccessChain, result_type, message_.fresh_id(), operands);
auto access_chain_instruction_ptr = access_chain_instruction.get();
instruction_to_insert_before->InsertBefore(
std::move(access_chain_instruction));
ir_context->get_def_use_mgr()->AnalyzeInstDefUse(
access_chain_instruction_ptr);
ir_context->set_instr_block(access_chain_instruction_ptr, enclosing_block);
// If the base pointer's pointee value was irrelevant, the same is true of
// the pointee value of the result of this access chain.
if (transformation_context->GetFactManager()->PointeeValueIsIrrelevant(
message_.pointer_id())) {
transformation_context->GetFactManager()->AddFactValueOfPointeeIsIrrelevant(
message_.fresh_id());
}
}
protobufs::Transformation TransformationAccessChain::ToMessage() const {
protobufs::Transformation result;
*result.mutable_access_chain() = message_;
return result;
}
std::pair<bool, uint32_t> TransformationAccessChain::GetIndexValue(
opt::IRContext* ir_context, uint32_t index_id,
uint32_t object_type_id) const {
if (!ValidIndexToComposite(ir_context, index_id, object_type_id)) {
return {false, 0};
}
auto index_instruction = ir_context->get_def_use_mgr()->GetDef(index_id);
uint32_t bound = fuzzerutil::GetBoundForCompositeIndex(
*ir_context->get_def_use_mgr()->GetDef(object_type_id), ir_context);
// The index must be a constant
if (!spvOpcodeIsConstant(index_instruction->opcode())) {
return {false, 0};
}
// The index must be in bounds.
uint32_t value = index_instruction->GetSingleWordInOperand(0);
if (value >= bound) {
return {false, 0};
}
return {true, value};
}
bool TransformationAccessChain::ValidIndexToComposite(
opt::IRContext* ir_context, uint32_t index_id, uint32_t object_type_id) {
auto object_type_def = ir_context->get_def_use_mgr()->GetDef(object_type_id);
// The object being indexed must be a composite.
if (!spvOpcodeIsComposite(object_type_def->opcode())) {
return false;
}
// Get the defining instruction of the index.
auto index_instruction = ir_context->get_def_use_mgr()->GetDef(index_id);
if (!index_instruction) {
return false;
}
// The index type must be 32-bit integer.
auto index_type =
ir_context->get_def_use_mgr()->GetDef(index_instruction->type_id());
if (index_type->opcode() != SpvOpTypeInt ||
index_type->GetSingleWordInOperand(0) != 32) {
return false;
}
// If the object being traversed is a struct, the id must correspond to an
// in-bound constant.
if (object_type_def->opcode() == SpvOpTypeStruct) {
if (!spvOpcodeIsConstant(index_instruction->opcode())) {
return false;
}
}
return true;
}
std::unordered_set<uint32_t> TransformationAccessChain::GetFreshIds() const {
std::unordered_set<uint32_t> result = {message_.fresh_id()};
for (auto& fresh_ids_for_clamping : message_.fresh_ids_for_clamping()) {
result.insert(fresh_ids_for_clamping.first());
result.insert(fresh_ids_for_clamping.second());
}
return result;
}
} // namespace fuzz
} // namespace spvtools