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// Copyright (c) 2019 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/fuzzer_util.h"
namespace spvtools {
namespace fuzz {
namespace fuzzerutil {
bool IsFreshId(opt::IRContext* context, uint32_t id) {
return !context->get_def_use_mgr()->GetDef(id);
}
void UpdateModuleIdBound(opt::IRContext* context, uint32_t id) {
// TODO(https://github.com/KhronosGroup/SPIRV-Tools/issues/2541) consider the
// case where the maximum id bound is reached.
context->module()->SetIdBound(
std::max(context->module()->id_bound(), id + 1));
}
opt::BasicBlock* MaybeFindBlock(opt::IRContext* context,
uint32_t maybe_block_id) {
auto inst = context->get_def_use_mgr()->GetDef(maybe_block_id);
if (inst == nullptr) {
// No instruction defining this id was found.
return nullptr;
}
if (inst->opcode() != SpvOpLabel) {
// The instruction defining the id is not a label, so it cannot be a block
// id.
return nullptr;
}
return context->cfg()->block(maybe_block_id);
}
bool PhiIdsOkForNewEdge(
opt::IRContext* context, opt::BasicBlock* bb_from, opt::BasicBlock* bb_to,
const google::protobuf::RepeatedField<google::protobuf::uint32>& phi_ids) {
if (bb_from->IsSuccessor(bb_to)) {
// There is already an edge from |from_block| to |to_block|, so there is
// no need to extend OpPhi instructions. Do not allow phi ids to be
// present. This might turn out to be too strict; perhaps it would be OK
// just to ignore the ids in this case.
return phi_ids.empty();
}
// The edge would add a previously non-existent edge from |from_block| to
// |to_block|, so we go through the given phi ids and check that they exactly
// match the OpPhi instructions in |to_block|.
uint32_t phi_index = 0;
// An explicit loop, rather than applying a lambda to each OpPhi in |bb_to|,
// makes sense here because we need to increment |phi_index| for each OpPhi
// instruction.
for (auto& inst : *bb_to) {
if (inst.opcode() != SpvOpPhi) {
// The OpPhi instructions all occur at the start of the block; if we find
// a non-OpPhi then we have seen them all.
break;
}
if (phi_index == static_cast<uint32_t>(phi_ids.size())) {
// Not enough phi ids have been provided to account for the OpPhi
// instructions.
return false;
}
// Look for an instruction defining the next phi id.
opt::Instruction* phi_extension =
context->get_def_use_mgr()->GetDef(phi_ids[phi_index]);
if (!phi_extension) {
// The id given to extend this OpPhi does not exist.
return false;
}
if (phi_extension->type_id() != inst.type_id()) {
// The instruction given to extend this OpPhi either does not have a type
// or its type does not match that of the OpPhi.
return false;
}
if (context->get_instr_block(phi_extension)) {
// The instruction defining the phi id has an associated block (i.e., it
// is not a global value). Check whether its definition dominates the
// exit of |from_block|.
auto dominator_analysis =
context->GetDominatorAnalysis(bb_from->GetParent());
if (!dominator_analysis->Dominates(phi_extension,
bb_from->terminator())) {
// The given id is no good as its definition does not dominate the exit
// of |from_block|
return false;
}
}
phi_index++;
}
// Return false if not all of the ids for extending OpPhi instructions are
// needed. This might turn out to be stricter than necessary; perhaps it would
// be OK just to not use the ids in this case.
return phi_index == static_cast<uint32_t>(phi_ids.size());
}
void AddUnreachableEdgeAndUpdateOpPhis(
opt::IRContext* context, opt::BasicBlock* bb_from, opt::BasicBlock* bb_to,
bool condition_value,
const google::protobuf::RepeatedField<google::protobuf::uint32>& phi_ids) {
assert(PhiIdsOkForNewEdge(context, bb_from, bb_to, phi_ids) &&
"Precondition on phi_ids is not satisfied");
assert(bb_from->terminator()->opcode() == SpvOpBranch &&
"Precondition on terminator of bb_from is not satisfied");
// Get the id of the boolean constant to be used as the condition.
opt::analysis::Bool bool_type;
opt::analysis::BoolConstant bool_constant(
context->get_type_mgr()->GetRegisteredType(&bool_type)->AsBool(),
condition_value);
uint32_t bool_id = context->get_constant_mgr()->FindDeclaredConstant(
&bool_constant, context->get_type_mgr()->GetId(&bool_type));
const bool from_to_edge_already_exists = bb_from->IsSuccessor(bb_to);
auto successor = bb_from->terminator()->GetSingleWordInOperand(0);
// Add the dead branch, by turning OpBranch into OpBranchConditional, and
// ordering the targets depending on whether the given boolean corresponds to
// true or false.
bb_from->terminator()->SetOpcode(SpvOpBranchConditional);
bb_from->terminator()->SetInOperands(
{{SPV_OPERAND_TYPE_ID, {bool_id}},
{SPV_OPERAND_TYPE_ID, {condition_value ? successor : bb_to->id()}},
{SPV_OPERAND_TYPE_ID, {condition_value ? bb_to->id() : successor}}});
// Update OpPhi instructions in the target block if this branch adds a
// previously non-existent edge from source to target.
if (!from_to_edge_already_exists) {
uint32_t phi_index = 0;
for (auto& inst : *bb_to) {
if (inst.opcode() != SpvOpPhi) {
break;
}
assert(phi_index < static_cast<uint32_t>(phi_ids.size()) &&
"There should be exactly one phi id per OpPhi instruction.");
inst.AddOperand({SPV_OPERAND_TYPE_ID, {phi_ids[phi_index]}});
inst.AddOperand({SPV_OPERAND_TYPE_ID, {bb_from->id()}});
phi_index++;
}
assert(phi_index == static_cast<uint32_t>(phi_ids.size()) &&
"There should be exactly one phi id per OpPhi instruction.");
}
}
bool BlockIsInLoopContinueConstruct(opt::IRContext* context, uint32_t block_id,
uint32_t maybe_loop_header_id) {
// We deem a block to be part of a loop's continue construct if the loop's
// continue target dominates the block.
auto containing_construct_block = context->cfg()->block(maybe_loop_header_id);
if (containing_construct_block->IsLoopHeader()) {
auto continue_target = containing_construct_block->ContinueBlockId();
if (context->GetDominatorAnalysis(containing_construct_block->GetParent())
->Dominates(continue_target, block_id)) {
return true;
}
}
return false;
}
opt::BasicBlock::iterator GetIteratorForInstruction(
opt::BasicBlock* block, const opt::Instruction* inst) {
for (auto inst_it = block->begin(); inst_it != block->end(); ++inst_it) {
if (inst == &*inst_it) {
return inst_it;
}
}
return block->end();
}
bool NewEdgeRespectsUseDefDominance(opt::IRContext* context,
opt::BasicBlock* bb_from,
opt::BasicBlock* bb_to) {
assert(bb_from->terminator()->opcode() == SpvOpBranch);
// If there is *already* an edge from |bb_from| to |bb_to|, then adding
// another edge is fine from a dominance point of view.
if (bb_from->terminator()->GetSingleWordInOperand(0) == bb_to->id()) {
return true;
}
// TODO(https://github.com/KhronosGroup/SPIRV-Tools/issues/2919): the
// solution below to determining whether a new edge respects dominance
// rules is incomplete. Test
// TransformationAddDeadContinueTest::DISABLED_Miscellaneous6 exposes the
// problem. In practice, this limitation does not bite too often, and the
// worst it does is leads to SPIR-V that spirv-val rejects.
// Let us assume that the module being manipulated is valid according to the
// rules of the SPIR-V language.
//
// Suppose that some block Y is dominated by |bb_to| (which includes the case
// where Y = |bb_to|).
//
// Suppose that Y uses an id i that is defined in some other block X.
//
// Because the module is valid, X must dominate Y. We are concerned about
// whether an edge from |bb_from| to |bb_to| could *stop* X from dominating
// Y.
//
// Because |bb_to| dominates Y, a new edge from |bb_from| to |bb_to| can
// only affect whether X dominates Y if X dominates |bb_to|.
//
// So let us assume that X does dominate |bb_to|, so that we have:
//
// (X defines i) dominates |bb_to| dominates (Y uses i)
//
// The new edge from |bb_from| to |bb_to| will stop the definition of i in X
// from dominating the use of i in Y exactly when the new edge will stop X
// from dominating |bb_to|.
//
// Now, the block X that we are worried about cannot dominate |bb_from|,
// because in that case X would still dominate |bb_to| after we add an edge
// from |bb_from| to |bb_to|.
//
// Also, it cannot be that X = |bb_to|, because nothing can stop a block
// from dominating itself.
//
// So we are looking for a block X such that:
//
// - X strictly dominates |bb_to|
// - X does not dominate |bb_from|
// - X defines an id i
// - i is used in some block Y
// - |bb_to| dominates Y
// Walk the dominator tree backwards, starting from the immediate dominator
// of |bb_to|. We can stop when we find a block that also dominates
// |bb_from|.
auto dominator_analysis = context->GetDominatorAnalysis(bb_from->GetParent());
for (auto dominator = dominator_analysis->ImmediateDominator(bb_to);
dominator != nullptr &&
!dominator_analysis->Dominates(dominator, bb_from);
dominator = dominator_analysis->ImmediateDominator(dominator)) {
// |dominator| is a candidate for block X in the above description.
// We now look through the instructions for a candidate instruction i.
for (auto& inst : *dominator) {
// Consider all the uses of this instruction.
if (!context->get_def_use_mgr()->WhileEachUse(
&inst,
[bb_to, context, dominator_analysis](
opt::Instruction* user, uint32_t operand_index) -> bool {
// If this use is in an OpPhi, we need to check that dominance
// of the relevant *parent* block is not spoiled. Otherwise we
// need to check that dominance of the block containing the use
// is not spoiled.
opt::BasicBlock* use_block_or_phi_parent =
user->opcode() == SpvOpPhi
? context->cfg()->block(
user->GetSingleWordOperand(operand_index + 1))
: context->get_instr_block(user);
// There might not be any relevant block, e.g. if the use is in
// a decoration; in this case the new edge is unproblematic.
if (use_block_or_phi_parent == nullptr) {
return true;
}
// With reference to the above discussion,
// |use_block_or_phi_parent| is a candidate for the block Y.
// If |bb_to| dominates this block, the new edge would be
// problematic.
return !dominator_analysis->Dominates(bb_to,
use_block_or_phi_parent);
})) {
return false;
}
}
}
return true;
}
bool BlockIsReachableInItsFunction(opt::IRContext* context,
opt::BasicBlock* bb) {
auto enclosing_function = bb->GetParent();
return context->GetDominatorAnalysis(enclosing_function)
->Dominates(enclosing_function->entry().get(), bb);
}
bool CanInsertOpcodeBeforeInstruction(
SpvOp opcode, const opt::BasicBlock::iterator& instruction_in_block) {
if (instruction_in_block->PreviousNode() &&
(instruction_in_block->PreviousNode()->opcode() == SpvOpLoopMerge ||
instruction_in_block->PreviousNode()->opcode() == SpvOpSelectionMerge)) {
// We cannot insert directly after a merge instruction.
return false;
}
if (opcode != SpvOpVariable &&
instruction_in_block->opcode() == SpvOpVariable) {
// We cannot insert a non-OpVariable instruction directly before a
// variable; variables in a function must be contiguous in the entry block.
return false;
}
// We cannot insert a non-OpPhi instruction directly before an OpPhi, because
// OpPhi instructions need to be contiguous at the start of a block.
return opcode == SpvOpPhi || instruction_in_block->opcode() != SpvOpPhi;
}
bool CanMakeSynonymOf(opt::IRContext* ir_context, opt::Instruction* inst) {
if (!inst->HasResultId()) {
// We can only make a synonym of an instruction that generates an id.
return false;
}
if (!inst->type_id()) {
// We can only make a synonym of an instruction that has a type.
return false;
}
// We do not make synonyms of objects that have decorations: if the synonym is
// not decorated analogously, using the original object vs. its synonymous
// form may not be equivalent.
return ir_context->get_decoration_mgr()
->GetDecorationsFor(inst->result_id(), true)
.empty();
}
bool IsCompositeType(const opt::analysis::Type* type) {
return type && (type->AsArray() || type->AsMatrix() || type->AsStruct() ||
type->AsVector());
}
std::vector<uint32_t> RepeatedFieldToVector(
const google::protobuf::RepeatedField<uint32_t>& repeated_field) {
std::vector<uint32_t> result;
for (auto i : repeated_field) {
result.push_back(i);
}
return result;
}
uint32_t WalkCompositeTypeIndices(
opt::IRContext* context, uint32_t base_object_type_id,
const google::protobuf::RepeatedField<google::protobuf::uint32>& indices) {
uint32_t sub_object_type_id = base_object_type_id;
for (auto index : indices) {
auto should_be_composite_type =
context->get_def_use_mgr()->GetDef(sub_object_type_id);
assert(should_be_composite_type && "The type should exist.");
if (SpvOpTypeArray == should_be_composite_type->opcode()) {
auto array_length = GetArraySize(*should_be_composite_type, context);
if (array_length == 0 || index >= array_length) {
return 0;
}
sub_object_type_id = should_be_composite_type->GetSingleWordInOperand(0);
} else if (SpvOpTypeMatrix == should_be_composite_type->opcode()) {
auto matrix_column_count =
should_be_composite_type->GetSingleWordInOperand(1);
if (index >= matrix_column_count) {
return 0;
}
sub_object_type_id = should_be_composite_type->GetSingleWordInOperand(0);
} else if (SpvOpTypeStruct == should_be_composite_type->opcode()) {
if (index >= GetNumberOfStructMembers(*should_be_composite_type)) {
return 0;
}
sub_object_type_id =
should_be_composite_type->GetSingleWordInOperand(index);
} else if (SpvOpTypeVector == should_be_composite_type->opcode()) {
auto vector_length = should_be_composite_type->GetSingleWordInOperand(1);
if (index >= vector_length) {
return 0;
}
sub_object_type_id = should_be_composite_type->GetSingleWordInOperand(0);
} else {
return 0;
}
}
return sub_object_type_id;
}
uint32_t GetNumberOfStructMembers(
const opt::Instruction& struct_type_instruction) {
assert(struct_type_instruction.opcode() == SpvOpTypeStruct &&
"An OpTypeStruct instruction is required here.");
return struct_type_instruction.NumInOperands();
}
uint32_t GetArraySize(const opt::Instruction& array_type_instruction,
opt::IRContext* context) {
auto array_length_constant =
context->get_constant_mgr()
->GetConstantFromInst(context->get_def_use_mgr()->GetDef(
array_type_instruction.GetSingleWordInOperand(1)))
->AsIntConstant();
if (array_length_constant->words().size() != 1) {
return 0;
}
return array_length_constant->GetU32();
}
} // namespace fuzzerutil
} // namespace fuzz
} // namespace spvtools