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// Copyright (c) 2017 Google Inc.
//
// 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.
#ifndef LIBSPIRV_UTIL_FOLD_H_
#define LIBSPIRV_UTIL_FOLD_H_
#include <cstdint>
#include <vector>
#include "const_folding_rules.h"
#include "constants.h"
#include "def_use_manager.h"
#include "folding_rules.h"
namespace spvtools {
namespace opt {
class InstructionFolder {
public:
// Returns the result of folding a scalar instruction with the given |opcode|
// and |operands|. Each entry in |operands| is a pointer to an
// analysis::Constant instance, which should've been created with the constant
// manager (See IRContext::get_constant_mgr).
//
// It is an error to call this function with an opcode that does not pass the
// IsFoldableOpcode test. If any error occurs during folding, the folder will
// fail with a call to assert.
uint32_t FoldScalars(
SpvOp opcode,
const std::vector<const analysis::Constant*>& operands) const;
// Returns the result of performing an operation with the given |opcode| over
// constant vectors with |num_dims| dimensions. Each entry in |operands| is a
// pointer to an analysis::Constant instance, which should've been created
// with the constant manager (See IRContext::get_constant_mgr).
//
// This function iterates through the given vector type constant operands and
// calculates the result for each element of the result vector to return.
// Vectors with longer than 32-bit scalar components are not accepted in this
// function.
//
// It is an error to call this function with an opcode that does not pass the
// IsFoldableOpcode test. If any error occurs during folding, the folder will
// fail with a call to assert.
std::vector<uint32_t> FoldVectors(
SpvOp opcode, uint32_t num_dims,
const std::vector<const analysis::Constant*>& operands) const;
// Returns true if |opcode| represents an operation handled by FoldScalars or
// FoldVectors.
bool IsFoldableOpcode(SpvOp opcode) const;
// Returns true if |cst| is supported by FoldScalars and FoldVectors.
bool IsFoldableConstant(const analysis::Constant* cst) const;
// Returns true if |FoldInstructionToConstant| could fold an instruction whose
// result type is |type_inst|.
bool IsFoldableType(opt::Instruction* type_inst) const;
// Tries to fold |inst| to a single constant, when the input ids to |inst|
// have been substituted using |id_map|. Returns a pointer to the OpConstant*
// instruction if successful. If necessary, a new constant instruction is
// created and placed in the global values section.
//
// |id_map| is a function that takes one result id and returns another. It
// can be used for things like CCP where it is known that some ids contain a
// constant, but the instruction itself has not been updated yet. This can
// map those ids to the appropriate constants.
opt::Instruction* FoldInstructionToConstant(
opt::Instruction* inst, std::function<uint32_t(uint32_t)> id_map) const;
// Returns true if |inst| can be folded into a simpler instruction.
// If |inst| can be simplified, |inst| is overwritten with the simplified
// instruction reusing the same result id.
//
// If |inst| is simplified, it is possible that the resulting code in invalid
// because the instruction is in a bad location. Callers of this function
// have to handle the following cases:
//
// 1) An OpPhi becomes and OpCopyObject - If there are OpPhi instruction after
// |inst| in a basic block then this is invalid. The caller must fix this
// up.
bool FoldInstruction(opt::Instruction* inst) const;
// Return true if this opcode has a const folding rule associtated with it.
bool HasConstFoldingRule(SpvOp opcode) const {
return GetConstantFoldingRules().HasFoldingRule(opcode);
}
private:
// Returns a reference to the ConstnatFoldingRules instance.
const ConstantFoldingRules& GetConstantFoldingRules() const {
return const_folding_rules;
}
// Returns a reference to the FoldingRules instance.
const FoldingRules& GetFoldingRules() const { return folding_rules; }
// Returns the single-word result from performing the given unary operation on
// the operand value which is passed in as a 32-bit word.
uint32_t UnaryOperate(SpvOp opcode, uint32_t operand) const;
// Returns the single-word result from performing the given binary operation
// on the operand values which are passed in as two 32-bit word.
uint32_t BinaryOperate(SpvOp opcode, uint32_t a, uint32_t b) const;
// Returns the single-word result from performing the given ternary operation
// on the operand values which are passed in as three 32-bit word.
uint32_t TernaryOperate(SpvOp opcode, uint32_t a, uint32_t b,
uint32_t c) const;
// Returns the single-word result from performing the given operation on the
// operand words. This only works with 32-bit operations and uses boolean
// convention that 0u is false, and anything else is boolean true.
// TODO(qining): Support operands other than 32-bit wide.
uint32_t OperateWords(SpvOp opcode,
const std::vector<uint32_t>& operand_words) const;
bool FoldInstructionInternal(opt::Instruction* inst) const;
// Returns true if |inst| is a binary operation that takes two integers as
// parameters and folds to a constant that can be represented as an unsigned
// 32-bit value when the ids have been replaced by |id_map|. If |inst| can be
// folded, the resulting value is returned in |*result|. Valid result types
// for the instruction are any integer (signed or unsigned) with 32-bits or
// less, or a boolean value.
bool FoldBinaryIntegerOpToConstant(
Instruction* inst, const std::function<uint32_t(uint32_t)>& id_map,
uint32_t* result) const;
// Returns true if |inst| is a binary operation on two boolean values, and
// folds
// to a constant boolean value when the ids have been replaced using |id_map|.
// If |inst| can be folded, the result value is returned in |*result|.
bool FoldBinaryBooleanOpToConstant(
Instruction* inst, const std::function<uint32_t(uint32_t)>& id_map,
uint32_t* result) const;
// Returns true if |inst| can be folded to an constant when the ids have been
// substituted using id_map. If it can, the value is returned in |result|. If
// not, |result| is unchanged. It is assumed that not all operands are
// constant. Those cases are handled by |FoldScalar|.
bool FoldIntegerOpToConstant(Instruction* inst,
const std::function<uint32_t(uint32_t)>& id_map,
uint32_t* result) const;
// Folding rules used by |FoldInstructionToConstant| and |FoldInstruction|.
ConstantFoldingRules const_folding_rules;
// Folding rules used by |FoldInstruction|.
FoldingRules folding_rules;
};
} // namespace opt
} // namespace spvtools
#endif // LIBSPIRV_UTIL_FOLD_H_
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