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// 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
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
#include "source/fuzz/transformation.h"
namespace spvtools {
namespace fuzz {
class TransformationFlattenConditionalBranch : public Transformation {
explicit TransformationFlattenConditionalBranch(
protobufs::TransformationFlattenConditionalBranch message);
uint32_t header_block_id, bool true_branch_first,
uint32_t fresh_id_for_bvec2_selector,
uint32_t fresh_id_for_bvec3_selector,
uint32_t fresh_id_for_bvec4_selector,
const std::vector<protobufs::SideEffectWrapperInfo>&
// - |message_.header_block_id| must be the label id of a reachable selection
// header, which ends with an OpBranchConditional instruction.
// - The condition of the OpBranchConditional instruction must not be an
// irrelevant id.
// - The header block and the merge block must describe a single-entry,
// single-exit region.
// - The region must not contain barrier or OpSampledImage instructions.
// - The region must not contain selection or loop constructs.
// - The region must not define ids that are the base objects for existing
// synonym facts.
// - For each instruction that requires additional fresh ids, then:
// - if the instruction is mapped to the required ids for enclosing it by
// |message_.side_effect_wrapper_info|, these must be valid (the
// fresh ids must be non-zero, fresh and distinct);
// - if there is no such mapping, the transformation context must have
// overflow ids available.
bool IsApplicable(
opt::IRContext* ir_context,
const TransformationContext& transformation_context) const override;
// Flattens the selection construct with header |message_.header_block_id|,
// changing any OpPhi in the block where the flow converges to OpSelect and
// enclosing any instruction with side effects in conditionals so that
// they are only executed when they should.
void Apply(opt::IRContext* ir_context,
TransformationContext* transformation_context) const override;
std::unordered_set<uint32_t> GetFreshIds() const override;
protobufs::Transformation ToMessage() const override;
// Returns true if the conditional headed by |header| can be flattened,
// according to the conditions of the IsApplicable method, assuming that
// enough fresh ids would be provided. In this case, it fills the
// |instructions_that_need_ids| set with all the instructions that would
// require fresh ids.
// Returns false otherwise.
// Assumes that |header| is the header of a conditional, so its last two
// 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
// inside a conditional. So, it returns:
// - true if the instruction has a non-void result id,
// - false if the instruction does not have a result id or has a void result
// id.
// Assumes that the instruction has side effects, requiring it to be enclosed
// inside a conditional, and that it can be enclosed inside a conditional
// keeping the module valid. Assumes that, if the instruction has a void
// result type, its result id is not used in the module.
static bool InstructionNeedsPlaceholder(opt::IRContext* ir_context,
const opt::Instruction& instruction);
// Returns true if and only if the SPIR-V version is such that the arguments
// to OpSelect are restricted to only scalars, pointers (if the appropriate
// capability is enabled) and component-wise vectors.
static bool OpSelectArgumentsAreRestricted(opt::IRContext* ir_context);
// Find the first block where flow converges (it is not necessarily the merge
// block) by walking the true branch until reaching a block that post-
// dominates the header.
// This is necessary because a potential common set of blocks at the end of
// the construct should not be duplicated.
static uint32_t FindConvergenceBlock(opt::IRContext* ir_context,
const opt::BasicBlock& header_block);
// Returns an unordered_map mapping instructions to the info required to
// enclose them inside a conditional. It maps the instructions to the
// corresponding entry in |message_.side_effect_wrapper_info|.
std::unordered_map<opt::Instruction*, protobufs::SideEffectWrapperInfo>
GetInstructionsToWrapperInfo(opt::IRContext* ir_context) const;
// Splits the given block, adding a new selection construct so that the given
// instruction is only executed if the boolean value of |condition_id| matches
// the value of |exec_if_cond_true|.
// Assumes that all parameters are consistent.
// 2 fresh ids are required if the instruction does not have a result id (the
// first two ids in |wrapper_info| must be valid fresh ids), 5 otherwise.
// Returns the merge block created.
// |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.
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);
// Turns every OpPhi instruction of |convergence_block| -- the convergence
// block for |header_block| (both in |ir_context|) into an OpSelect
// instruction.
void RewriteOpPhiInstructionsAtConvergenceBlock(
const opt::BasicBlock& header_block, uint32_t convergence_block_id,
opt::IRContext* ir_context) const;
// Adds an OpCompositeExtract instruction to the start of |block| in
// |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.
static void AddBooleanVectorConstructorToBlock(
uint32_t fresh_id, uint32_t dimension,
const opt::Operand& branch_condition_operand, opt::IRContext* ir_context,
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.
static bool InstructionCanBeHandled(opt::IRContext* ir_context,
const opt::Instruction& instruction);
protobufs::TransformationFlattenConditionalBranch message_;
} // namespace fuzz
} // namespace spvtools