From 75344955fcd43b67cedec8d5b29ad3419b5aaa81 Mon Sep 17 00:00:00 2001 From: Evgeniy Stepanov Date: Thu, 15 Aug 2019 22:58:28 +0000 Subject: [PATCH] Move isPointerOffset function to ValueTracking (NFC). Summary: To be reused in MemTag sanitizer. Reviewers: pcc, vitalybuka, ostannard Subscribers: hiraditya, llvm-commits Tags: #llvm Differential Revision: https://reviews.llvm.org/D66165 llvm-svn: 369062 --- llvm/include/llvm/Analysis/ValueTracking.h | 6 ++ llvm/lib/Analysis/ValueTracking.cpp | 83 +++++++++++++++++ .../lib/Transforms/Scalar/MemCpyOptimizer.cpp | 88 +------------------ 3 files changed, 91 insertions(+), 86 deletions(-) diff --git a/llvm/include/llvm/Analysis/ValueTracking.h b/llvm/include/llvm/Analysis/ValueTracking.h index 79aaf52b75de..bd37cbe2ec71 100644 --- a/llvm/include/llvm/Analysis/ValueTracking.h +++ b/llvm/include/llvm/Analysis/ValueTracking.h @@ -660,6 +660,12 @@ class Value; Optional isImpliedByDomCondition(const Value *Cond, const Instruction *ContextI, const DataLayout &DL); + + /// Return true if Ptr1 is provably equal to Ptr2 plus a constant offset, and + /// return that constant offset. For example, Ptr1 might be &A[42], and Ptr2 + /// might be &A[40]. In this case offset would be -8. + bool isPointerOffset(Value *Ptr1, Value *Ptr2, int64_t &Offset, + const DataLayout &DL); } // end namespace llvm #endif // LLVM_ANALYSIS_VALUETRACKING_H diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp index 74293dbc973b..8027c2706ee4 100644 --- a/llvm/lib/Analysis/ValueTracking.cpp +++ b/llvm/lib/Analysis/ValueTracking.cpp @@ -5701,3 +5701,86 @@ ConstantRange llvm::computeConstantRange(const Value *V, bool UseInstrInfo) { return CR; } + +static int64_t getOffsetFromIndex(const GEPOperator *GEP, unsigned Idx, + bool &VariableIdxFound, + const DataLayout &DL) { + // Skip over the first indices. + gep_type_iterator GTI = gep_type_begin(GEP); + for (unsigned i = 1; i != Idx; ++i, ++GTI) + /*skip along*/; + + // Compute the offset implied by the rest of the indices. + int64_t Offset = 0; + for (unsigned i = Idx, e = GEP->getNumOperands(); i != e; ++i, ++GTI) { + ConstantInt *OpC = dyn_cast(GEP->getOperand(i)); + if (!OpC) + return VariableIdxFound = true; + if (OpC->isZero()) + continue; // No offset. + + // Handle struct indices, which add their field offset to the pointer. + if (StructType *STy = GTI.getStructTypeOrNull()) { + Offset += DL.getStructLayout(STy)->getElementOffset(OpC->getZExtValue()); + continue; + } + + // Otherwise, we have a sequential type like an array or vector. Multiply + // the index by the ElementSize. + uint64_t Size = DL.getTypeAllocSize(GTI.getIndexedType()); + Offset += Size * OpC->getSExtValue(); + } + + return Offset; +} + +bool llvm::isPointerOffset(Value *Ptr1, Value *Ptr2, int64_t &Offset, + const DataLayout &DL) { + Ptr1 = Ptr1->stripPointerCasts(); + Ptr2 = Ptr2->stripPointerCasts(); + + // Handle the trivial case first. + if (Ptr1 == Ptr2) { + Offset = 0; + return true; + } + + GEPOperator *GEP1 = dyn_cast(Ptr1); + GEPOperator *GEP2 = dyn_cast(Ptr2); + + bool VariableIdxFound = false; + + // If one pointer is a GEP and the other isn't, then see if the GEP is a + // constant offset from the base, as in "P" and "gep P, 1". + if (GEP1 && !GEP2 && GEP1->getOperand(0)->stripPointerCasts() == Ptr2) { + Offset = -getOffsetFromIndex(GEP1, 1, VariableIdxFound, DL); + return !VariableIdxFound; + } + + if (GEP2 && !GEP1 && GEP2->getOperand(0)->stripPointerCasts() == Ptr1) { + Offset = getOffsetFromIndex(GEP2, 1, VariableIdxFound, DL); + return !VariableIdxFound; + } + + // Right now we handle the case when Ptr1/Ptr2 are both GEPs with an identical + // base. After that base, they may have some number of common (and + // potentially variable) indices. After that they handle some constant + // offset, which determines their offset from each other. At this point, we + // handle no other case. + if (!GEP1 || !GEP2 || GEP1->getOperand(0) != GEP2->getOperand(0)) + return false; + + // Skip any common indices and track the GEP types. + unsigned Idx = 1; + for (; Idx != GEP1->getNumOperands() && Idx != GEP2->getNumOperands(); ++Idx) + if (GEP1->getOperand(Idx) != GEP2->getOperand(Idx)) + break; + + int64_t Offset1 = getOffsetFromIndex(GEP1, Idx, VariableIdxFound, DL); + int64_t Offset2 = getOffsetFromIndex(GEP2, Idx, VariableIdxFound, DL); + if (VariableIdxFound) + return false; + + Offset = Offset2 - Offset1; + return true; +} diff --git a/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp b/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp index 5a055139be4f..79bf6e05c4c0 100644 --- a/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp +++ b/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp @@ -69,90 +69,6 @@ STATISTIC(NumMemSetInfer, "Number of memsets inferred"); STATISTIC(NumMoveToCpy, "Number of memmoves converted to memcpy"); STATISTIC(NumCpyToSet, "Number of memcpys converted to memset"); -static int64_t GetOffsetFromIndex(const GEPOperator *GEP, unsigned Idx, - bool &VariableIdxFound, - const DataLayout &DL) { - // Skip over the first indices. - gep_type_iterator GTI = gep_type_begin(GEP); - for (unsigned i = 1; i != Idx; ++i, ++GTI) - /*skip along*/; - - // Compute the offset implied by the rest of the indices. - int64_t Offset = 0; - for (unsigned i = Idx, e = GEP->getNumOperands(); i != e; ++i, ++GTI) { - ConstantInt *OpC = dyn_cast(GEP->getOperand(i)); - if (!OpC) - return VariableIdxFound = true; - if (OpC->isZero()) continue; // No offset. - - // Handle struct indices, which add their field offset to the pointer. - if (StructType *STy = GTI.getStructTypeOrNull()) { - Offset += DL.getStructLayout(STy)->getElementOffset(OpC->getZExtValue()); - continue; - } - - // Otherwise, we have a sequential type like an array or vector. Multiply - // the index by the ElementSize. - uint64_t Size = DL.getTypeAllocSize(GTI.getIndexedType()); - Offset += Size*OpC->getSExtValue(); - } - - return Offset; -} - -/// Return true if Ptr1 is provably equal to Ptr2 plus a constant offset, and -/// return that constant offset. For example, Ptr1 might be &A[42], and Ptr2 -/// might be &A[40]. In this case offset would be -8. -static bool IsPointerOffset(Value *Ptr1, Value *Ptr2, int64_t &Offset, - const DataLayout &DL) { - Ptr1 = Ptr1->stripPointerCasts(); - Ptr2 = Ptr2->stripPointerCasts(); - - // Handle the trivial case first. - if (Ptr1 == Ptr2) { - Offset = 0; - return true; - } - - GEPOperator *GEP1 = dyn_cast(Ptr1); - GEPOperator *GEP2 = dyn_cast(Ptr2); - - bool VariableIdxFound = false; - - // If one pointer is a GEP and the other isn't, then see if the GEP is a - // constant offset from the base, as in "P" and "gep P, 1". - if (GEP1 && !GEP2 && GEP1->getOperand(0)->stripPointerCasts() == Ptr2) { - Offset = -GetOffsetFromIndex(GEP1, 1, VariableIdxFound, DL); - return !VariableIdxFound; - } - - if (GEP2 && !GEP1 && GEP2->getOperand(0)->stripPointerCasts() == Ptr1) { - Offset = GetOffsetFromIndex(GEP2, 1, VariableIdxFound, DL); - return !VariableIdxFound; - } - - // Right now we handle the case when Ptr1/Ptr2 are both GEPs with an identical - // base. After that base, they may have some number of common (and - // potentially variable) indices. After that they handle some constant - // offset, which determines their offset from each other. At this point, we - // handle no other case. - if (!GEP1 || !GEP2 || GEP1->getOperand(0) != GEP2->getOperand(0)) - return false; - - // Skip any common indices and track the GEP types. - unsigned Idx = 1; - for (; Idx != GEP1->getNumOperands() && Idx != GEP2->getNumOperands(); ++Idx) - if (GEP1->getOperand(Idx) != GEP2->getOperand(Idx)) - break; - - int64_t Offset1 = GetOffsetFromIndex(GEP1, Idx, VariableIdxFound, DL); - int64_t Offset2 = GetOffsetFromIndex(GEP2, Idx, VariableIdxFound, DL); - if (VariableIdxFound) return false; - - Offset = Offset2-Offset1; - return true; -} - namespace { /// Represents a range of memset'd bytes with the ByteVal value. @@ -420,7 +336,7 @@ Instruction *MemCpyOptPass::tryMergingIntoMemset(Instruction *StartInst, // Check to see if this store is to a constant offset from the start ptr. int64_t Offset; - if (!IsPointerOffset(StartPtr, NextStore->getPointerOperand(), Offset, + if (!isPointerOffset(StartPtr, NextStore->getPointerOperand(), Offset, DL)) break; @@ -434,7 +350,7 @@ Instruction *MemCpyOptPass::tryMergingIntoMemset(Instruction *StartInst, // Check to see if this store is to a constant offset from the start ptr. int64_t Offset; - if (!IsPointerOffset(StartPtr, MSI->getDest(), Offset, DL)) + if (!isPointerOffset(StartPtr, MSI->getDest(), Offset, DL)) break; Ranges.addMemSet(Offset, MSI);