1 // Copyright (c) 2017 Google Inc. 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // http://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 15 #ifndef SOURCE_OPT_FOLD_H_ 16 #define SOURCE_OPT_FOLD_H_ 17 18 #include <cstdint> 19 #include <vector> 20 21 #include "source/opt/const_folding_rules.h" 22 #include "source/opt/constants.h" 23 #include "source/opt/def_use_manager.h" 24 #include "source/opt/folding_rules.h" 25 26 namespace spvtools { 27 namespace opt { 28 29 class InstructionFolder { 30 public: InstructionFolder(IRContext * context)31 explicit InstructionFolder(IRContext* context) 32 : context_(context), 33 const_folding_rules_(new ConstantFoldingRules(context)), 34 folding_rules_(new FoldingRules(context)) { 35 folding_rules_->AddFoldingRules(); 36 const_folding_rules_->AddFoldingRules(); 37 } 38 InstructionFolder(IRContext * context,std::unique_ptr<FoldingRules> && folding_rules,std::unique_ptr<ConstantFoldingRules> && constant_folding_rules)39 explicit InstructionFolder( 40 IRContext* context, std::unique_ptr<FoldingRules>&& folding_rules, 41 std::unique_ptr<ConstantFoldingRules>&& constant_folding_rules) 42 : context_(context), 43 const_folding_rules_(std::move(constant_folding_rules)), 44 folding_rules_(std::move(folding_rules)) { 45 folding_rules_->AddFoldingRules(); 46 const_folding_rules_->AddFoldingRules(); 47 } 48 49 // Returns the result of folding a scalar instruction with the given |opcode| 50 // and |operands|. Each entry in |operands| is a pointer to an 51 // analysis::Constant instance, which should've been created with the constant 52 // manager (See IRContext::get_constant_mgr). 53 // 54 // It is an error to call this function with an opcode that does not pass the 55 // IsFoldableOpcode test. If any error occurs during folding, the folder will 56 // fail with a call to assert. 57 uint32_t FoldScalars( 58 SpvOp opcode, 59 const std::vector<const analysis::Constant*>& operands) const; 60 61 // Returns the result of performing an operation with the given |opcode| over 62 // constant vectors with |num_dims| dimensions. Each entry in |operands| is a 63 // pointer to an analysis::Constant instance, which should've been created 64 // with the constant manager (See IRContext::get_constant_mgr). 65 // 66 // This function iterates through the given vector type constant operands and 67 // calculates the result for each element of the result vector to return. 68 // Vectors with longer than 32-bit scalar components are not accepted in this 69 // function. 70 // 71 // It is an error to call this function with an opcode that does not pass the 72 // IsFoldableOpcode test. If any error occurs during folding, the folder will 73 // fail with a call to assert. 74 std::vector<uint32_t> FoldVectors( 75 SpvOp opcode, uint32_t num_dims, 76 const std::vector<const analysis::Constant*>& operands) const; 77 78 // Returns true if |opcode| represents an operation handled by FoldScalars or 79 // FoldVectors. 80 bool IsFoldableOpcode(SpvOp opcode) const; 81 82 // Returns true if |cst| is supported by FoldScalars and FoldVectors. 83 bool IsFoldableConstant(const analysis::Constant* cst) const; 84 85 // Returns true if |FoldInstructionToConstant| could fold an instruction whose 86 // result type is |type_inst|. 87 bool IsFoldableType(Instruction* type_inst) const; 88 89 // Tries to fold |inst| to a single constant, when the input ids to |inst| 90 // have been substituted using |id_map|. Returns a pointer to the OpConstant* 91 // instruction if successful. If necessary, a new constant instruction is 92 // created and placed in the global values section. 93 // 94 // |id_map| is a function that takes one result id and returns another. It 95 // can be used for things like CCP where it is known that some ids contain a 96 // constant, but the instruction itself has not been updated yet. This can 97 // map those ids to the appropriate constants. 98 Instruction* FoldInstructionToConstant( 99 Instruction* inst, std::function<uint32_t(uint32_t)> id_map) const; 100 // Returns true if |inst| can be folded into a simpler instruction. 101 // If |inst| can be simplified, |inst| is overwritten with the simplified 102 // instruction reusing the same result id. 103 // 104 // If |inst| is simplified, it is possible that the resulting code in invalid 105 // because the instruction is in a bad location. Callers of this function 106 // have to handle the following cases: 107 // 108 // 1) An OpPhi becomes and OpCopyObject - If there are OpPhi instruction after 109 // |inst| in a basic block then this is invalid. The caller must fix this 110 // up. 111 bool FoldInstruction(Instruction* inst) const; 112 113 // Return true if this opcode has a const folding rule associtated with it. HasConstFoldingRule(const Instruction * inst)114 bool HasConstFoldingRule(const Instruction* inst) const { 115 return GetConstantFoldingRules().HasFoldingRule(inst); 116 } 117 118 private: 119 // Returns a reference to the ConstnatFoldingRules instance. GetConstantFoldingRules()120 const ConstantFoldingRules& GetConstantFoldingRules() const { 121 return *const_folding_rules_; 122 } 123 124 // Returns a reference to the FoldingRules instance. GetFoldingRules()125 const FoldingRules& GetFoldingRules() const { return *folding_rules_; } 126 127 // Returns the single-word result from performing the given unary operation on 128 // the operand value which is passed in as a 32-bit word. 129 uint32_t UnaryOperate(SpvOp opcode, uint32_t operand) const; 130 131 // Returns the single-word result from performing the given binary operation 132 // on the operand values which are passed in as two 32-bit word. 133 uint32_t BinaryOperate(SpvOp opcode, uint32_t a, uint32_t b) const; 134 135 // Returns the single-word result from performing the given ternary operation 136 // on the operand values which are passed in as three 32-bit word. 137 uint32_t TernaryOperate(SpvOp opcode, uint32_t a, uint32_t b, 138 uint32_t c) const; 139 140 // Returns the single-word result from performing the given operation on the 141 // operand words. This only works with 32-bit operations and uses boolean 142 // convention that 0u is false, and anything else is boolean true. 143 // TODO(qining): Support operands other than 32-bit wide. 144 uint32_t OperateWords(SpvOp opcode, 145 const std::vector<uint32_t>& operand_words) const; 146 147 bool FoldInstructionInternal(Instruction* inst) const; 148 149 // Returns true if |inst| is a binary operation that takes two integers as 150 // parameters and folds to a constant that can be represented as an unsigned 151 // 32-bit value when the ids have been replaced by |id_map|. If |inst| can be 152 // folded, the resulting value is returned in |*result|. Valid result types 153 // for the instruction are any integer (signed or unsigned) with 32-bits or 154 // less, or a boolean value. 155 bool FoldBinaryIntegerOpToConstant( 156 Instruction* inst, const std::function<uint32_t(uint32_t)>& id_map, 157 uint32_t* result) const; 158 159 // Returns true if |inst| is a binary operation on two boolean values, and 160 // folds 161 // to a constant boolean value when the ids have been replaced using |id_map|. 162 // If |inst| can be folded, the result value is returned in |*result|. 163 bool FoldBinaryBooleanOpToConstant( 164 Instruction* inst, const std::function<uint32_t(uint32_t)>& id_map, 165 uint32_t* result) const; 166 167 // Returns true if |inst| can be folded to an constant when the ids have been 168 // substituted using id_map. If it can, the value is returned in |result|. If 169 // not, |result| is unchanged. It is assumed that not all operands are 170 // constant. Those cases are handled by |FoldScalar|. 171 bool FoldIntegerOpToConstant(Instruction* inst, 172 const std::function<uint32_t(uint32_t)>& id_map, 173 uint32_t* result) const; 174 175 IRContext* context_; 176 177 // Folding rules used by |FoldInstructionToConstant| and |FoldInstruction|. 178 std::unique_ptr<ConstantFoldingRules> const_folding_rules_; 179 180 // Folding rules used by |FoldInstruction|. 181 std::unique_ptr<FoldingRules> folding_rules_; 182 }; 183 184 } // namespace opt 185 } // namespace spvtools 186 187 #endif // SOURCE_OPT_FOLD_H_ 188