SPIRV-Tools/source/opt/const_folding_rules.cpp
Alan Baker 802cf053c7 Merge arithmetic with non-trivial constant operands
Adding basis of arithmetic merging

* Refactored constant collection in ConstantManager
* New rules:
 * consecutive negates
 * negate of arithmetic op with a constant
 * consecutive muls
 * reciprocal of div

* Removed IRContext::CanFoldFloatingPoint
 * replaced by Instruction::IsFloatingPointFoldingAllowed
* Fixed some bad tests
* added some header comments

Added PerformIntegerOperation

* minor fixes to constants and tests
* fixed IntMultiplyBy1 to work with 64 bit ints
* added tests for integer mul merging

Adding test for vector integer multiply merging

Adding support for merging integer add and sub through negate

* Added tests

Adding rules to merge mult with preceding divide

* Has a couple tests, but needs more
* Added more comments

Fixed bug in integer division folding

* Will no longer merge through integer division if there would be a
remainder in the division
* Added a bunch more tests

Adding rules to merge divide and multiply through divide

* Improved comments
* Added tests

Adding rules to handle mul or div of a negation

* Added tests

Changes for review

* Early exit if no constants are involved in more functions
* fixed some comments
* removed unused declaration
* clarified some logic

Adding new rules for add and subtract

* Fold adds of adds, subtracts or negates
* Fold subtracts of adds, subtracts or negates
* Added tests
2018-02-27 13:02:13 -05:00

312 lines
14 KiB
C++

// Copyright (c) 2018 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 "const_folding_rules.h"
namespace spvtools {
namespace opt {
namespace {
const uint32_t kExtractCompositeIdInIdx = 0;
// Folds an OpcompositeExtract where input is a composite constant.
ConstantFoldingRule FoldExtractWithConstants() {
return [](ir::Instruction* inst,
const std::vector<const analysis::Constant*>& constants)
-> const analysis::Constant* {
const analysis::Constant* c = constants[kExtractCompositeIdInIdx];
if (c == nullptr) {
return nullptr;
}
for (uint32_t i = 1; i < inst->NumInOperands(); ++i) {
uint32_t element_index = inst->GetSingleWordInOperand(i);
if (c->AsNullConstant()) {
// Return Null for the return type.
ir::IRContext* context = inst->context();
analysis::ConstantManager* const_mgr = context->get_constant_mgr();
analysis::TypeManager* type_mgr = context->get_type_mgr();
return const_mgr->GetConstant(type_mgr->GetType(inst->type_id()), {});
}
auto cc = c->AsCompositeConstant();
assert(cc != nullptr);
auto components = cc->GetComponents();
c = components[element_index];
}
return c;
};
}
ConstantFoldingRule FoldCompositeWithConstants() {
// Folds an OpCompositeConstruct where all of the inputs are constants to a
// constant. A new constant is created if necessary.
return [](ir::Instruction* inst,
const std::vector<const analysis::Constant*>& constants)
-> const analysis::Constant* {
ir::IRContext* context = inst->context();
analysis::ConstantManager* const_mgr = context->get_constant_mgr();
analysis::TypeManager* type_mgr = context->get_type_mgr();
const analysis::Type* new_type = type_mgr->GetType(inst->type_id());
std::vector<uint32_t> ids;
for (const analysis::Constant* element_const : constants) {
if (element_const == nullptr) {
return nullptr;
}
uint32_t element_id = const_mgr->FindDeclaredConstant(element_const);
if (element_id == 0) {
return nullptr;
}
ids.push_back(element_id);
}
return const_mgr->GetConstant(new_type, ids);
};
}
// The interface for a function that returns the result of applying a scalar
// floating-point binary operation on |a| and |b|. The type of the return value
// will be |type|. The input constants must also be of type |type|.
using FloatScalarFoldingRule = std::function<const analysis::Constant*(
const analysis::Type* result_type, const analysis::Constant* a,
const analysis::Constant* b, analysis::ConstantManager*)>;
// Returns an std::vector containing the elements of |constant|. The type of
// |constant| must be |Vector|.
std::vector<const analysis::Constant*> GetVectorComponents(
const analysis::Constant* constant, analysis::ConstantManager* const_mgr) {
std::vector<const analysis::Constant*> components;
const analysis::VectorConstant* a = constant->AsVectorConstant();
const analysis::Vector* vector_type = constant->type()->AsVector();
assert(vector_type != nullptr);
if (a != nullptr) {
for (uint32_t i = 0; i < vector_type->element_count(); ++i) {
components.push_back(a->GetComponents()[i]);
}
} else {
const analysis::Type* element_type = vector_type->element_type();
const analysis::Constant* element_null_const =
const_mgr->GetConstant(element_type, {});
for (uint32_t i = 0; i < vector_type->element_count(); ++i) {
components.push_back(element_null_const);
}
}
return components;
}
// Returns a |ConstantFoldingRule| that folds floating point scalars using
// |scalar_rule| and vectors of floating point by applying |scalar_rule| to the
// elements of the vector. The |ConstantFoldingRule| that is returned assumes
// that |constants| contains 2 entries. If they are not |nullptr|, then their
// type is either |Float| or a |Vector| whose element type is |Float|.
ConstantFoldingRule FoldFloatingPointOp(FloatScalarFoldingRule scalar_rule) {
return [scalar_rule](ir::Instruction* inst,
const std::vector<const analysis::Constant*>& constants)
-> const analysis::Constant* {
ir::IRContext* context = inst->context();
analysis::ConstantManager* const_mgr = context->get_constant_mgr();
analysis::TypeManager* type_mgr = context->get_type_mgr();
const analysis::Type* result_type = type_mgr->GetType(inst->type_id());
const analysis::Vector* vector_type = result_type->AsVector();
if (!inst->IsFloatingPointFoldingAllowed()) {
return nullptr;
}
if (constants[0] == nullptr || constants[1] == nullptr) {
return nullptr;
}
if (vector_type != nullptr) {
std::vector<const analysis::Constant*> a_components;
std::vector<const analysis::Constant*> b_components;
std::vector<const analysis::Constant*> results_components;
a_components = GetVectorComponents(constants[0], const_mgr);
b_components = GetVectorComponents(constants[1], const_mgr);
// Fold each component of the vector.
for (uint32_t i = 0; i < a_components.size(); ++i) {
results_components.push_back(scalar_rule(vector_type->element_type(),
a_components[i],
b_components[i], const_mgr));
if (results_components[i] == nullptr) {
return nullptr;
}
}
// Build the constant object and return it.
std::vector<uint32_t> ids;
for (const analysis::Constant* member : results_components) {
ids.push_back(const_mgr->GetDefiningInstruction(member)->result_id());
}
return const_mgr->GetConstant(vector_type, ids);
} else {
return scalar_rule(result_type, constants[0], constants[1], const_mgr);
}
};
}
// This macro defines a |FloatScalarFoldingRule| that applies |op|. The
// operator |op| must work for both float and double, and use syntax "f1 op f2".
#define FOLD_FPARITH_OP(op) \
[](const analysis::Type* result_type, const analysis::Constant* a, \
const analysis::Constant* b, \
analysis::ConstantManager* const_mgr) -> const analysis::Constant* { \
assert(result_type != nullptr && a != nullptr && b != nullptr); \
assert(result_type == a->type() && result_type == b->type()); \
const analysis::Float* float_type = result_type->AsFloat(); \
assert(float_type != nullptr); \
if (float_type->width() == 32) { \
float fa = a->GetFloat(); \
float fb = b->GetFloat(); \
spvutils::FloatProxy<float> result(fa op fb); \
std::vector<uint32_t> words = result.GetWords(); \
return const_mgr->GetConstant(result_type, words); \
} else if (float_type->width() == 64) { \
double fa = a->GetDouble(); \
double fb = b->GetDouble(); \
spvutils::FloatProxy<double> result(fa op fb); \
std::vector<uint32_t> words = result.GetWords(); \
return const_mgr->GetConstant(result_type, words); \
} \
return nullptr; \
}
// Define the folding rules for subtraction, addition, multiplication, and
// division for floating point values.
ConstantFoldingRule FoldFSub() {
return FoldFloatingPointOp(FOLD_FPARITH_OP(-));
}
ConstantFoldingRule FoldFAdd() {
return FoldFloatingPointOp(FOLD_FPARITH_OP(+));
}
ConstantFoldingRule FoldFMul() {
return FoldFloatingPointOp(FOLD_FPARITH_OP(*));
}
ConstantFoldingRule FoldFDiv() {
return FoldFloatingPointOp(FOLD_FPARITH_OP(/));
}
bool CompareFloatingPoint(bool op_result, bool op_unordered,
bool need_ordered) {
if (need_ordered) {
// operands are ordered and Operand 1 is |op| Operand 2
return !op_unordered && op_result;
} else {
// operands are unordered or Operand 1 is |op| Operand 2
return op_unordered || op_result;
}
}
// This macro defines a |FloatScalarFoldingRule| that applies |op|. The
// operator |op| must work for both float and double, and use syntax "f1 op f2".
#define FOLD_FPCMP_OP(op, ord) \
[](const analysis::Type* result_type, const analysis::Constant* a, \
const analysis::Constant* b, \
analysis::ConstantManager* const_mgr) -> const analysis::Constant* { \
assert(result_type != nullptr && a != nullptr && b != nullptr); \
assert(result_type->AsBool()); \
assert(a->type() == b->type()); \
const analysis::Float* float_type = a->type()->AsFloat(); \
assert(float_type != nullptr); \
if (float_type->width() == 32) { \
float fa = a->GetFloat(); \
float fb = b->GetFloat(); \
bool result = CompareFloatingPoint( \
fa op fb, std::isnan(fa) || std::isnan(fb), ord); \
std::vector<uint32_t> words = {uint32_t(result)}; \
return const_mgr->GetConstant(result_type, words); \
} else if (float_type->width() == 64) { \
double fa = a->GetDouble(); \
double fb = b->GetDouble(); \
bool result = CompareFloatingPoint( \
fa op fb, std::isnan(fa) || std::isnan(fb), ord); \
std::vector<uint32_t> words = {uint32_t(result)}; \
return const_mgr->GetConstant(result_type, words); \
} \
return nullptr; \
}
// Define the folding rules for ordered and unordered comparison for floating
// point values.
ConstantFoldingRule FoldFOrdEqual() {
return FoldFloatingPointOp(FOLD_FPCMP_OP(==, true));
}
ConstantFoldingRule FoldFUnordEqual() {
return FoldFloatingPointOp(FOLD_FPCMP_OP(==, false));
}
ConstantFoldingRule FoldFOrdNotEqual() {
return FoldFloatingPointOp(FOLD_FPCMP_OP(!=, true));
}
ConstantFoldingRule FoldFUnordNotEqual() {
return FoldFloatingPointOp(FOLD_FPCMP_OP(!=, false));
}
ConstantFoldingRule FoldFOrdLessThan() {
return FoldFloatingPointOp(FOLD_FPCMP_OP(<, true));
}
ConstantFoldingRule FoldFUnordLessThan() {
return FoldFloatingPointOp(FOLD_FPCMP_OP(<, false));
}
ConstantFoldingRule FoldFOrdGreaterThan() {
return FoldFloatingPointOp(FOLD_FPCMP_OP(>, true));
}
ConstantFoldingRule FoldFUnordGreaterThan() {
return FoldFloatingPointOp(FOLD_FPCMP_OP(>, false));
}
ConstantFoldingRule FoldFOrdLessThanEqual() {
return FoldFloatingPointOp(FOLD_FPCMP_OP(<=, true));
}
ConstantFoldingRule FoldFUnordLessThanEqual() {
return FoldFloatingPointOp(FOLD_FPCMP_OP(<=, false));
}
ConstantFoldingRule FoldFOrdGreaterThanEqual() {
return FoldFloatingPointOp(FOLD_FPCMP_OP(>=, true));
}
ConstantFoldingRule FoldFUnordGreaterThanEqual() {
return FoldFloatingPointOp(FOLD_FPCMP_OP(>=, false));
}
} // namespace
spvtools::opt::ConstantFoldingRules::ConstantFoldingRules() {
// Add all folding rules to the list for the opcodes to which they apply.
// Note that the order in which rules are added to the list matters. If a rule
// applies to the instruction, the rest of the rules will not be attempted.
// Take that into consideration.
rules_[SpvOpCompositeConstruct].push_back(FoldCompositeWithConstants());
rules_[SpvOpCompositeExtract].push_back(FoldExtractWithConstants());
rules_[SpvOpFAdd].push_back(FoldFAdd());
rules_[SpvOpFDiv].push_back(FoldFDiv());
rules_[SpvOpFMul].push_back(FoldFMul());
rules_[SpvOpFSub].push_back(FoldFSub());
rules_[SpvOpFOrdEqual].push_back(FoldFOrdEqual());
rules_[SpvOpFUnordEqual].push_back(FoldFUnordEqual());
rules_[SpvOpFOrdNotEqual].push_back(FoldFOrdNotEqual());
rules_[SpvOpFUnordNotEqual].push_back(FoldFUnordNotEqual());
rules_[SpvOpFOrdLessThan].push_back(FoldFOrdLessThan());
rules_[SpvOpFUnordLessThan].push_back(FoldFUnordLessThan());
rules_[SpvOpFOrdGreaterThan].push_back(FoldFOrdGreaterThan());
rules_[SpvOpFUnordGreaterThan].push_back(FoldFUnordGreaterThan());
rules_[SpvOpFOrdLessThanEqual].push_back(FoldFOrdLessThanEqual());
rules_[SpvOpFUnordLessThanEqual].push_back(FoldFUnordLessThanEqual());
rules_[SpvOpFOrdGreaterThanEqual].push_back(FoldFOrdGreaterThanEqual());
rules_[SpvOpFUnordGreaterThanEqual].push_back(FoldFUnordGreaterThanEqual());
}
} // namespace opt
} // namespace spvtools