1 //===-- Operator.cpp - Implement the LLVM operators -----------------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This file implements the non-inline methods for the LLVM Operator classes. 10 // 11 //===----------------------------------------------------------------------===// 12 13 #include "llvm/IR/Operator.h" 14 #include "llvm/IR/DataLayout.h" 15 #include "llvm/IR/GetElementPtrTypeIterator.h" 16 #include "llvm/IR/Instructions.h" 17 #include "llvm/IR/Type.h" 18 19 #include "ConstantsContext.h" 20 21 namespace llvm { 22 Type *GEPOperator::getSourceElementType() const { 23 if (auto *I = dyn_cast<GetElementPtrInst>(this)) 24 return I->getSourceElementType(); 25 return cast<GetElementPtrConstantExpr>(this)->getSourceElementType(); 26 } 27 28 Type *GEPOperator::getResultElementType() const { 29 if (auto *I = dyn_cast<GetElementPtrInst>(this)) 30 return I->getResultElementType(); 31 return cast<GetElementPtrConstantExpr>(this)->getResultElementType(); 32 } 33 34 Align GEPOperator::getMaxPreservedAlignment(const DataLayout &DL) const { 35 /// compute the worse possible offset for every level of the GEP et accumulate 36 /// the minimum alignment into Result. 37 38 Align Result = Align(llvm::Value::MaximumAlignment); 39 for (gep_type_iterator GTI = gep_type_begin(this), GTE = gep_type_end(this); 40 GTI != GTE; ++GTI) { 41 int64_t Offset = 1; 42 ConstantInt *OpC = dyn_cast<ConstantInt>(GTI.getOperand()); 43 44 if (StructType *STy = GTI.getStructTypeOrNull()) { 45 const StructLayout *SL = DL.getStructLayout(STy); 46 Offset = SL->getElementOffset(OpC->getZExtValue()); 47 } else { 48 assert(GTI.isSequential() && "should be sequencial"); 49 /// If the index isn't know we take 1 because it is the index that will 50 /// give the worse alignment of the offset. 51 int64_t ElemCount = 1; 52 if (OpC) 53 ElemCount = OpC->getZExtValue(); 54 Offset = DL.getTypeAllocSize(GTI.getIndexedType()) * ElemCount; 55 } 56 Result = Align(MinAlign(Offset, Result.value())); 57 } 58 return Result; 59 } 60 61 bool GEPOperator::accumulateConstantOffset( 62 const DataLayout &DL, APInt &Offset, 63 function_ref<bool(Value &, APInt &)> ExternalAnalysis) const { 64 assert(Offset.getBitWidth() == 65 DL.getIndexSizeInBits(getPointerAddressSpace()) && 66 "The offset bit width does not match DL specification."); 67 68 bool UsedExternalAnalysis = false; 69 auto AccumulateOffset = [&](APInt Index, uint64_t Size) -> bool { 70 Index = Index.sextOrTrunc(Offset.getBitWidth()); 71 APInt IndexedSize = APInt(Offset.getBitWidth(), Size); 72 // For array or vector indices, scale the index by the size of the type. 73 if (!UsedExternalAnalysis) { 74 Offset += Index * IndexedSize; 75 } else { 76 // External Analysis can return a result higher/lower than the value 77 // represents. We need to detect overflow/underflow. 78 bool Overflow = false; 79 APInt OffsetPlus = Index.smul_ov(IndexedSize, Overflow); 80 if (Overflow) 81 return false; 82 Offset = Offset.sadd_ov(OffsetPlus, Overflow); 83 if (Overflow) 84 return false; 85 } 86 return true; 87 }; 88 89 for (gep_type_iterator GTI = gep_type_begin(this), GTE = gep_type_end(this); 90 GTI != GTE; ++GTI) { 91 // Scalable vectors are multiplied by a runtime constant. 92 bool ScalableType = false; 93 if (isa<ScalableVectorType>(GTI.getIndexedType())) 94 ScalableType = true; 95 96 Value *V = GTI.getOperand(); 97 StructType *STy = GTI.getStructTypeOrNull(); 98 // Handle ConstantInt if possible. 99 if (auto ConstOffset = dyn_cast<ConstantInt>(V)) { 100 if (ConstOffset->isZero()) 101 continue; 102 // if the type is scalable and the constant is not zero (vscale * n * 0 = 103 // 0) bailout. 104 if (ScalableType) 105 return false; 106 // Handle a struct index, which adds its field offset to the pointer. 107 if (STy) { 108 unsigned ElementIdx = ConstOffset->getZExtValue(); 109 const StructLayout *SL = DL.getStructLayout(STy); 110 // Element offset is in bytes. 111 if (!AccumulateOffset( 112 APInt(Offset.getBitWidth(), SL->getElementOffset(ElementIdx)), 113 1)) 114 return false; 115 continue; 116 } 117 if (!AccumulateOffset(ConstOffset->getValue(), 118 DL.getTypeAllocSize(GTI.getIndexedType()))) 119 return false; 120 continue; 121 } 122 123 // The operand is not constant, check if an external analysis was provided. 124 // External analsis is not applicable to a struct type. 125 if (!ExternalAnalysis || STy || ScalableType) 126 return false; 127 APInt AnalysisIndex; 128 if (!ExternalAnalysis(*V, AnalysisIndex)) 129 return false; 130 UsedExternalAnalysis = true; 131 if (!AccumulateOffset(AnalysisIndex, 132 DL.getTypeAllocSize(GTI.getIndexedType()))) 133 return false; 134 } 135 return true; 136 } 137 } // namespace llvm 138