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) : context_(context) {} 32 33 // Returns the result of folding a scalar instruction with the given |opcode| 34 // and |operands|. Each entry in |operands| is a pointer to an 35 // analysis::Constant instance, which should've been created with the constant 36 // manager (See IRContext::get_constant_mgr). 37 // 38 // It is an error to call this function with an opcode that does not pass the 39 // IsFoldableOpcode test. If any error occurs during folding, the folder will 40 // fail with a call to assert. 41 uint32_t FoldScalars( 42 SpvOp opcode, 43 const std::vector<const analysis::Constant*>& operands) const; 44 45 // Returns the result of performing an operation with the given |opcode| over 46 // constant vectors with |num_dims| dimensions. Each entry in |operands| is a 47 // pointer to an analysis::Constant instance, which should've been created 48 // with the constant manager (See IRContext::get_constant_mgr). 49 // 50 // This function iterates through the given vector type constant operands and 51 // calculates the result for each element of the result vector to return. 52 // Vectors with longer than 32-bit scalar components are not accepted in this 53 // function. 54 // 55 // It is an error to call this function with an opcode that does not pass the 56 // IsFoldableOpcode test. If any error occurs during folding, the folder will 57 // fail with a call to assert. 58 std::vector<uint32_t> FoldVectors( 59 SpvOp opcode, uint32_t num_dims, 60 const std::vector<const analysis::Constant*>& operands) const; 61 62 // Returns true if |opcode| represents an operation handled by FoldScalars or 63 // FoldVectors. 64 bool IsFoldableOpcode(SpvOp opcode) const; 65 66 // Returns true if |cst| is supported by FoldScalars and FoldVectors. 67 bool IsFoldableConstant(const analysis::Constant* cst) const; 68 69 // Returns true if |FoldInstructionToConstant| could fold an instruction whose 70 // result type is |type_inst|. 71 bool IsFoldableType(Instruction* type_inst) const; 72 73 // Tries to fold |inst| to a single constant, when the input ids to |inst| 74 // have been substituted using |id_map|. Returns a pointer to the OpConstant* 75 // instruction if successful. If necessary, a new constant instruction is 76 // created and placed in the global values section. 77 // 78 // |id_map| is a function that takes one result id and returns another. It 79 // can be used for things like CCP where it is known that some ids contain a 80 // constant, but the instruction itself has not been updated yet. This can 81 // map those ids to the appropriate constants. 82 Instruction* FoldInstructionToConstant( 83 Instruction* inst, std::function<uint32_t(uint32_t)> id_map) const; 84 // Returns true if |inst| can be folded into a simpler instruction. 85 // If |inst| can be simplified, |inst| is overwritten with the simplified 86 // instruction reusing the same result id. 87 // 88 // If |inst| is simplified, it is possible that the resulting code in invalid 89 // because the instruction is in a bad location. Callers of this function 90 // have to handle the following cases: 91 // 92 // 1) An OpPhi becomes and OpCopyObject - If there are OpPhi instruction after 93 // |inst| in a basic block then this is invalid. The caller must fix this 94 // up. 95 bool FoldInstruction(Instruction* inst) const; 96 97 // Return true if this opcode has a const folding rule associtated with it. HasConstFoldingRule(SpvOp opcode)98 bool HasConstFoldingRule(SpvOp opcode) const { 99 return GetConstantFoldingRules().HasFoldingRule(opcode); 100 } 101 102 private: 103 // Returns a reference to the ConstnatFoldingRules instance. GetConstantFoldingRules()104 const ConstantFoldingRules& GetConstantFoldingRules() const { 105 return const_folding_rules; 106 } 107 108 // Returns a reference to the FoldingRules instance. GetFoldingRules()109 const FoldingRules& GetFoldingRules() const { return folding_rules; } 110 111 // Returns the single-word result from performing the given unary operation on 112 // the operand value which is passed in as a 32-bit word. 113 uint32_t UnaryOperate(SpvOp opcode, uint32_t operand) const; 114 115 // Returns the single-word result from performing the given binary operation 116 // on the operand values which are passed in as two 32-bit word. 117 uint32_t BinaryOperate(SpvOp opcode, uint32_t a, uint32_t b) const; 118 119 // Returns the single-word result from performing the given ternary operation 120 // on the operand values which are passed in as three 32-bit word. 121 uint32_t TernaryOperate(SpvOp opcode, uint32_t a, uint32_t b, 122 uint32_t c) const; 123 124 // Returns the single-word result from performing the given operation on the 125 // operand words. This only works with 32-bit operations and uses boolean 126 // convention that 0u is false, and anything else is boolean true. 127 // TODO(qining): Support operands other than 32-bit wide. 128 uint32_t OperateWords(SpvOp opcode, 129 const std::vector<uint32_t>& operand_words) const; 130 131 bool FoldInstructionInternal(Instruction* inst) const; 132 133 // Returns true if |inst| is a binary operation that takes two integers as 134 // parameters and folds to a constant that can be represented as an unsigned 135 // 32-bit value when the ids have been replaced by |id_map|. If |inst| can be 136 // folded, the resulting value is returned in |*result|. Valid result types 137 // for the instruction are any integer (signed or unsigned) with 32-bits or 138 // less, or a boolean value. 139 bool FoldBinaryIntegerOpToConstant( 140 Instruction* inst, const std::function<uint32_t(uint32_t)>& id_map, 141 uint32_t* result) const; 142 143 // Returns true if |inst| is a binary operation on two boolean values, and 144 // folds 145 // to a constant boolean value when the ids have been replaced using |id_map|. 146 // If |inst| can be folded, the result value is returned in |*result|. 147 bool FoldBinaryBooleanOpToConstant( 148 Instruction* inst, const std::function<uint32_t(uint32_t)>& id_map, 149 uint32_t* result) const; 150 151 // Returns true if |inst| can be folded to an constant when the ids have been 152 // substituted using id_map. If it can, the value is returned in |result|. If 153 // not, |result| is unchanged. It is assumed that not all operands are 154 // constant. Those cases are handled by |FoldScalar|. 155 bool FoldIntegerOpToConstant(Instruction* inst, 156 const std::function<uint32_t(uint32_t)>& id_map, 157 uint32_t* result) const; 158 159 IRContext* context_; 160 161 // Folding rules used by |FoldInstructionToConstant| and |FoldInstruction|. 162 ConstantFoldingRules const_folding_rules; 163 164 // Folding rules used by |FoldInstruction|. 165 FoldingRules folding_rules; 166 }; 167 168 } // namespace opt 169 } // namespace spvtools 170 171 #endif // SOURCE_OPT_FOLD_H_ 172