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spirv-fuzz: Fix bugs in TransformationFlattenConditionalBranch (#4006)

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Fixes #4005.
Fixes #3993.
This commit is contained in:
Vasyl Teliman 2020-11-03 17:03:08 +02:00 committed by GitHub
parent 5735576f87
commit aa6035f1c6
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GPG Key ID: 4AEE18F83AFDEB23
4 changed files with 197 additions and 72 deletions
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5
source/fuzz/fuzzer_pass_flatten_conditional_branches.cpp
View File

@ -71,7 +71,8 @@ void FuzzerPassFlattenConditionalBranches::Apply() {
// Do not consider this header if the conditional cannot be flattened.
if (!TransformationFlattenConditionalBranch::
GetProblematicInstructionsIfConditionalCanBeFlattened(
GetIRContext(), header, &instructions_that_need_ids)) {
GetIRContext(), header, *GetTransformationContext(),
&instructions_that_need_ids)) {
continue;
}
@ -214,7 +215,7 @@ void FuzzerPassFlattenConditionalBranches::Apply() {
}
}
wrappers_info.emplace_back(wrapper_info);
wrappers_info.push_back(std::move(wrapper_info));
}
// Apply the transformation, evenly choosing whether to lay out the true

161
source/fuzz/transformation_flatten_conditional_branch.cpp
View File

@ -82,65 +82,6 @@ bool TransformationFlattenConditionalBranch::IsApplicable(
}
}
if (OpSelectArgumentsAreRestricted(ir_context)) {
// OpPhi instructions at the convergence block for the selection are handled
// by turning them into OpSelect instructions. As the SPIR-V version in use
// has restrictions on the arguments that OpSelect can take, we must check
// that any OpPhi instructions are compatible with these restrictions.
uint32_t convergence_block_id =
FindConvergenceBlock(ir_context, *header_block);
// Consider every OpPhi instruction at the convergence block.
if (!ir_context->cfg()
->block(convergence_block_id)
->WhileEachPhiInst([this,
ir_context](opt::Instruction* inst) -> bool {
// Decide whether the OpPhi can be handled based on its result
// type.
opt::Instruction* phi_result_type =
ir_context->get_def_use_mgr()->GetDef(inst->type_id());
switch (phi_result_type->opcode()) {
case SpvOpTypeBool:
case SpvOpTypeInt:
case SpvOpTypeFloat:
case SpvOpTypePointer:
// Fine: OpSelect can work directly on scalar and pointer
// types.
return true;
case SpvOpTypeVector: {
// In its restricted form, OpSelect can only select between
// vectors if the condition of the select is a boolean
// boolean vector. We thus require the appropriate boolean
// vector type to be present.
uint32_t bool_type_id =
fuzzerutil::MaybeGetBoolType(ir_context);
uint32_t dimension =
phi_result_type->GetSingleWordInOperand(1);
if (fuzzerutil::MaybeGetVectorType(ir_context, bool_type_id,
dimension) == 0) {
// The required boolean vector type is not present.
return false;
}
// The transformation needs to be equipped with a fresh id
// in which to store the vectorized version of the selection
// construct's condition.
switch (dimension) {
case 2:
return message_.fresh_id_for_bvec2_selector() != 0;
case 3:
return message_.fresh_id_for_bvec3_selector() != 0;
default:
assert(dimension == 4 && "Invalid vector dimension.");
return message_.fresh_id_for_bvec4_selector() != 0;
}
}
default:
return false;
}
})) {
return false;
}
}
// Use a set to keep track of the instructions that require fresh ids.
std::set<opt::Instruction*> instructions_that_need_ids;
@ -148,7 +89,8 @@ bool TransformationFlattenConditionalBranch::IsApplicable(
// if so, add all the problematic instructions that need to be enclosed inside
// conditionals to |instructions_that_need_ids|.
if (!GetProblematicInstructionsIfConditionalCanBeFlattened(
ir_context, header_block, &instructions_that_need_ids)) {
ir_context, header_block, transformation_context,
&instructions_that_need_ids)) {
return false;
}
@ -205,6 +147,69 @@ bool TransformationFlattenConditionalBranch::IsApplicable(
}
}
if (OpSelectArgumentsAreRestricted(ir_context)) {
// OpPhi instructions at the convergence block for the selection are handled
// by turning them into OpSelect instructions. As the SPIR-V version in use
// has restrictions on the arguments that OpSelect can take, we must check
// that any OpPhi instructions are compatible with these restrictions.
uint32_t convergence_block_id =
FindConvergenceBlock(ir_context, *header_block);
// Consider every OpPhi instruction at the convergence block.
if (!ir_context->cfg()
->block(convergence_block_id)
->WhileEachPhiInst([this,
ir_context](opt::Instruction* inst) -> bool {
// Decide whether the OpPhi can be handled based on its result
// type.
opt::Instruction* phi_result_type =
ir_context->get_def_use_mgr()->GetDef(inst->type_id());
switch (phi_result_type->opcode()) {
case SpvOpTypeBool:
case SpvOpTypeInt:
case SpvOpTypeFloat:
case SpvOpTypePointer:
// Fine: OpSelect can work directly on scalar and pointer
// types.
return true;
case SpvOpTypeVector: {
// In its restricted form, OpSelect can only select between
// vectors if the condition of the select is a boolean
// boolean vector. We thus require the appropriate boolean
// vector type to be present.
uint32_t bool_type_id =
fuzzerutil::MaybeGetBoolType(ir_context);
if (!bool_type_id) {
return false;
}
uint32_t dimension =
phi_result_type->GetSingleWordInOperand(1);
if (fuzzerutil::MaybeGetVectorType(ir_context, bool_type_id,
dimension) == 0) {
// The required boolean vector type is not present.
return false;
}
// The transformation needs to be equipped with a fresh id
// in which to store the vectorized version of the selection
// construct's condition.
switch (dimension) {
case 2:
return message_.fresh_id_for_bvec2_selector() != 0;
case 3:
return message_.fresh_id_for_bvec3_selector() != 0;
default:
assert(dimension == 4 && "Invalid vector dimension.");
return message_.fresh_id_for_bvec4_selector() != 0;
}
}
default:
return false;
}
})) {
return false;
}
}
// All checks were passed.
return true;
}
@ -428,6 +433,7 @@ protobufs::Transformation TransformationFlattenConditionalBranch::ToMessage()
bool TransformationFlattenConditionalBranch::
GetProblematicInstructionsIfConditionalCanBeFlattened(
opt::IRContext* ir_context, opt::BasicBlock* header,
const TransformationContext& transformation_context,
std::set<opt::Instruction*>* instructions_that_need_ids) {
uint32_t merge_block_id = header->MergeBlockIdIfAny();
assert(merge_block_id &&
@ -441,6 +447,11 @@ bool TransformationFlattenConditionalBranch::
auto postdominator_analysis =
ir_context->GetPostDominatorAnalysis(enclosing_function);
// |header| must be reachable.
if (!dominator_analysis->IsReachable(header)) {
return false;
}
// Check that the header and the merge block describe a single-entry,
// single-exit region.
if (!dominator_analysis->Dominates(header->id(), merge_block_id) ||
@ -454,13 +465,22 @@ bool TransformationFlattenConditionalBranch::
// - they branch unconditionally to another block
// Add any side-effecting instruction, requiring fresh ids, to
// |instructions_that_need_ids|
std::list<uint32_t> to_check;
std::queue<uint32_t> to_check;
header->ForEachSuccessorLabel(
[&to_check](uint32_t label) { to_check.push_back(label); });
[&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_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
@ -470,6 +490,15 @@ bool TransformationFlattenConditionalBranch::
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
@ -518,7 +547,7 @@ bool TransformationFlattenConditionalBranch::
// Add the successor of this block to the list of blocks that need to be
// checked.
to_check.push_back(block->terminator()->GetSingleWordInOperand(0));
to_check.push(block->terminator()->GetSingleWordInOperand(0));
}
// All the blocks are compatible with the transformation and this is indeed a
@ -564,7 +593,7 @@ TransformationFlattenConditionalBranch::EncloseInstructionInConditional(
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) const {
std::vector<uint32_t>* irrelevant_ids) {
// Get the next instruction (it will be useful for splitting).
auto next_instruction = instruction->NextNode();
@ -810,7 +839,7 @@ bool TransformationFlattenConditionalBranch::OpSelectArgumentsAreRestricted(
void TransformationFlattenConditionalBranch::AddBooleanVectorConstructorToBlock(
uint32_t fresh_id, uint32_t dimension,
const opt::Operand& branch_condition_operand, opt::IRContext* ir_context,
opt::BasicBlock* block) const {
opt::BasicBlock* block) {
opt::Instruction::OperandList in_operands;
for (uint32_t i = 0; i < dimension; i++) {
in_operands.emplace_back(branch_condition_operand);

9
source/fuzz/transformation_flatten_conditional_branch.h
View File

@ -72,6 +72,7 @@ class TransformationFlattenConditionalBranch : public Transformation {
// instructions are OpSelectionMerge and OpBranchConditional.
static bool GetProblematicInstructionsIfConditionalCanBeFlattened(
opt::IRContext* ir_context, opt::BasicBlock* header,
const TransformationContext& transformation_context,
std::set<opt::Instruction*>* instructions_that_need_ids);
// Returns true iff the given instruction needs a placeholder to be enclosed
@ -117,14 +118,14 @@ class TransformationFlattenConditionalBranch : public Transformation {
// |dead_blocks| and |irrelevant_ids| are used to record the ids of blocks
// and instructions for which dead block and irrelevant id facts should
// ultimately be created.
opt::BasicBlock* EncloseInstructionInConditional(
static opt::BasicBlock* 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) const;
std::vector<uint32_t>* irrelevant_ids);
// Turns every OpPhi instruction of |convergence_block| -- the convergence
// block for |header_block| (both in |ir_context|) into an OpSelect
@ -137,10 +138,10 @@ class TransformationFlattenConditionalBranch : public Transformation {
// |ir_context|, with result id given by |fresh_id|. The instruction will
// make a |dimension|-dimensional boolean vector with
// |branch_condition_operand| at every component.
void AddBooleanVectorConstructorToBlock(
static void AddBooleanVectorConstructorToBlock(
uint32_t fresh_id, uint32_t dimension,
const opt::Operand& branch_condition_operand, opt::IRContext* ir_context,
opt::BasicBlock* block) const;
opt::BasicBlock* block);
// Returns true if the given instruction either has no side effects or it can
// be handled by being enclosed in a conditional.

94
test/fuzz/transformation_flatten_conditional_branch_test.cpp
View File

@ -2041,6 +2041,100 @@ TEST(TransformationFlattenConditionalBranchTest,
ASSERT_TRUE(IsEqual(env, expected, context.get()));
}
TEST(TransformationFlattenConditionalBranchTest, ContainsDeadBlocksTest) {
std::string shader = R"(
OpCapability Shader
%1 = OpExtInstImport "GLSL.std.450"
OpMemoryModel Logical GLSL450
OpEntryPoint Fragment %4 "main"
OpExecutionMode %4 OriginUpperLeft
OpSource ESSL 320
OpName %4 "main"
%2 = OpTypeVoid
%3 = OpTypeFunction %2
%6 = OpTypeBool
%7 = OpConstantFalse %6
%4 = OpFunction %2 None %3
%5 = OpLabel
OpSelectionMerge %9 None
OpBranchConditional %7 %8 %9
%8 = OpLabel
%10 = OpCopyObject %6 %7
OpBranch %9
%9 = OpLabel
%11 = OpPhi %6 %10 %8 %7 %5
%12 = OpPhi %6 %7 %5 %10 %8
OpReturn
OpFunctionEnd
)";
const auto env = SPV_ENV_UNIVERSAL_1_3;
const auto consumer = nullptr;
const auto context = BuildModule(env, consumer, shader, kFuzzAssembleOption);
spvtools::ValidatorOptions validator_options;
ASSERT_TRUE(fuzzerutil::IsValidAndWellFormed(context.get(), validator_options,
kConsoleMessageConsumer));
TransformationContext transformation_context(
MakeUnique<FactManager>(context.get()), validator_options);
TransformationFlattenConditionalBranch transformation(5, true, 0, 0, 0, {});
ASSERT_TRUE(
transformation.IsApplicable(context.get(), transformation_context));
transformation_context.GetFactManager()->AddFactBlockIsDead(8);
ASSERT_FALSE(
transformation.IsApplicable(context.get(), transformation_context));
}
TEST(TransformationFlattenConditionalBranchTest, ContainsContinueBlockTest) {
std::string shader = R"(
OpCapability Shader
%1 = OpExtInstImport "GLSL.std.450"
OpMemoryModel Logical GLSL450
OpEntryPoint Fragment %4 "main"
OpExecutionMode %4 OriginUpperLeft
OpSource ESSL 320
OpName %4 "main"
%2 = OpTypeVoid
%3 = OpTypeFunction %2
%6 = OpTypeBool
%7 = OpConstantFalse %6
%4 = OpFunction %2 None %3
%12 = OpLabel
OpBranch %13
%13 = OpLabel
OpLoopMerge %15 %14 None
OpBranchConditional %7 %5 %15
%5 = OpLabel
OpSelectionMerge %11 None
OpBranchConditional %7 %9 %10
%9 = OpLabel
OpBranch %11
%10 = OpLabel
OpBranch %14
%11 = OpLabel
OpBranch %14
%14 = OpLabel
OpBranch %13
%15 = OpLabel
OpReturn
OpFunctionEnd
)";
const auto env = SPV_ENV_UNIVERSAL_1_3;
const auto consumer = nullptr;
const auto context = BuildModule(env, consumer, shader, kFuzzAssembleOption);
spvtools::ValidatorOptions validator_options;
ASSERT_TRUE(fuzzerutil::IsValidAndWellFormed(context.get(), validator_options,
kConsoleMessageConsumer));
TransformationContext transformation_context(
MakeUnique<FactManager>(context.get()), validator_options);
ASSERT_FALSE(TransformationFlattenConditionalBranch(5, true, 0, 0, 0, {})
.IsApplicable(context.get(), transformation_context));
}
} // namespace
} // namespace fuzz
} // namespace spvtools