MemCpyOptimizer.cpp revision ac53a0b272452013124bfc70480aea5e41b60f40
121e463b2bf864671a87ebe386cb100ef9349a540Nate Begeman//===- MemCpyOptimizer.cpp - Optimize use of memcpy and friends -----------===// 27c5a3d390a463fb50a6eee7ae3174817925e6d28Chris Lattner// 37c5a3d390a463fb50a6eee7ae3174817925e6d28Chris Lattner// The LLVM Compiler Infrastructure 47c5a3d390a463fb50a6eee7ae3174817925e6d28Chris Lattner// 54ee451de366474b9c228b4e5fa573795a715216dChris Lattner// This file is distributed under the University of Illinois Open Source 64ee451de366474b9c228b4e5fa573795a715216dChris Lattner// License. See LICENSE.TXT for details. 77c5a3d390a463fb50a6eee7ae3174817925e6d28Chris Lattner// 87c5a3d390a463fb50a6eee7ae3174817925e6d28Chris Lattner//===----------------------------------------------------------------------===// 97c5a3d390a463fb50a6eee7ae3174817925e6d28Chris Lattner// 107c5a3d390a463fb50a6eee7ae3174817925e6d28Chris Lattner// This pass performs various transformations related to eliminating memcpy 117c5a3d390a463fb50a6eee7ae3174817925e6d28Chris Lattner// calls, or transforming sets of stores into memset's. 127c5a3d390a463fb50a6eee7ae3174817925e6d28Chris Lattner// 137c5a3d390a463fb50a6eee7ae3174817925e6d28Chris Lattner//===----------------------------------------------------------------------===// 147c5a3d390a463fb50a6eee7ae3174817925e6d28Chris Lattner 157c5a3d390a463fb50a6eee7ae3174817925e6d28Chris Lattner#define DEBUG_TYPE "memcpyopt" 167c5a3d390a463fb50a6eee7ae3174817925e6d28Chris Lattner#include "llvm/Transforms/Scalar.h" 177c5a3d390a463fb50a6eee7ae3174817925e6d28Chris Lattner#include "llvm/IntrinsicInst.h" 187c5a3d390a463fb50a6eee7ae3174817925e6d28Chris Lattner#include "llvm/Instructions.h" 190bbea954331b8f08afa5b094dfb0841829c70eaaChris Lattner#include "llvm/LLVMContext.h" 202668959b8879097db368aec7d76c455260abc75bChris Lattner#include "llvm/ADT/SmallVector.h" 21331d1bc5dfe1be9090e29f9af9579888a63a9a79Chris Lattner#include "llvm/ADT/Statistic.h" 227c5a3d390a463fb50a6eee7ae3174817925e6d28Chris Lattner#include "llvm/Analysis/Dominators.h" 237c5a3d390a463fb50a6eee7ae3174817925e6d28Chris Lattner#include "llvm/Analysis/AliasAnalysis.h" 240bbea954331b8f08afa5b094dfb0841829c70eaaChris Lattner#include "llvm/Analysis/MemoryDependenceAnalysis.h" 250bbea954331b8f08afa5b094dfb0841829c70eaaChris Lattner#include "llvm/Support/Debug.h" 263c983c3dc19bb83807f978c04737b4572be90a93Nate Begeman#include "llvm/Support/GetElementPtrTypeIterator.h" 270ba2bcfcc3149a25d08aa8aa00fb6c34a4e25bddDan Gohman#include "llvm/Support/raw_ostream.h" 280bbea954331b8f08afa5b094dfb0841829c70eaaChris Lattner#include "llvm/Target/TargetData.h" 290bbea954331b8f08afa5b094dfb0841829c70eaaChris Lattner#include <list> 300bbea954331b8f08afa5b094dfb0841829c70eaaChris Lattnerusing namespace llvm; 310bbea954331b8f08afa5b094dfb0841829c70eaaChris Lattner 32f76053269ecc6c7bd3d0b1e90ebdd0cef1bb2bdcChris LattnerSTATISTIC(NumMemCpyInstr, "Number of memcpy instructions deleted"); 33c09eeec0ebc378644bafd04916e5efafa7d98152Nate BegemanSTATISTIC(NumMemSetInfer, "Number of memsets inferred"); 34c09eeec0ebc378644bafd04916e5efafa7d98152Nate BegemanSTATISTIC(NumMoveToCpy, "Number of memmoves converted to memcpy"); 35c09eeec0ebc378644bafd04916e5efafa7d98152Nate Begeman 36c09eeec0ebc378644bafd04916e5efafa7d98152Nate Begeman/// isBytewiseValue - If the specified value can be set by repeating the same 37c09eeec0ebc378644bafd04916e5efafa7d98152Nate Begeman/// byte in memory, return the i8 value that it is represented with. This is 38c09eeec0ebc378644bafd04916e5efafa7d98152Nate Begeman/// true for all i8 values obviously, but is also true for i32 0, i32 -1, 39c09eeec0ebc378644bafd04916e5efafa7d98152Nate Begeman/// i16 0xF0F0, double 0.0 etc. If the value can't be handled with a repeated 40c09eeec0ebc378644bafd04916e5efafa7d98152Nate Begeman/// byte store (e.g. i16 0x1234), return null. 41c09eeec0ebc378644bafd04916e5efafa7d98152Nate Begemanstatic Value *isBytewiseValue(Value *V) { 42860e8862c1fbd3b261da4a64a8c0096f9f373681Chris Lattner LLVMContext &Context = V->getContext(); 435126984b1da4bda0e93961da07e883699f1f2d57Chris Lattner 445126984b1da4bda0e93961da07e883699f1f2d57Chris Lattner // All byte-wide stores are splatable, even of arbitrary variables. 455126984b1da4bda0e93961da07e883699f1f2d57Chris Lattner if (V->getType() == Type::getInt8Ty(Context)) return V; 465126984b1da4bda0e93961da07e883699f1f2d57Chris Lattner 475126984b1da4bda0e93961da07e883699f1f2d57Chris Lattner // Constant float and double values can be handled as integer values if the 48993aeb2ed93f99faf1438f1b67cd922989306828Nate Begeman // corresponding integer value is "byteable". An important case is 0.0. 49993aeb2ed93f99faf1438f1b67cd922989306828Nate Begeman if (ConstantFP *CFP = dyn_cast<ConstantFP>(V)) { 50993aeb2ed93f99faf1438f1b67cd922989306828Nate Begeman if (CFP->getType()->isFloatTy()) 51993aeb2ed93f99faf1438f1b67cd922989306828Nate Begeman V = ConstantExpr::getBitCast(CFP, Type::getInt32Ty(Context)); 52f1d0b2bedaa065972a5ba17259055c1176cd1497Chris Lattner if (CFP->getType()->isDoubleTy()) 53f1d0b2bedaa065972a5ba17259055c1176cd1497Chris Lattner V = ConstantExpr::getBitCast(CFP, Type::getInt64Ty(Context)); 54f1d0b2bedaa065972a5ba17259055c1176cd1497Chris Lattner // Don't handle long double formats, which have strange constraints. 55f1d0b2bedaa065972a5ba17259055c1176cd1497Chris Lattner } 56860e8862c1fbd3b261da4a64a8c0096f9f373681Chris Lattner 57860e8862c1fbd3b261da4a64a8c0096f9f373681Chris Lattner // We can handle constant integers that are power of two in size and a 58860e8862c1fbd3b261da4a64a8c0096f9f373681Chris Lattner // multiple of 8 bits. 59860e8862c1fbd3b261da4a64a8c0096f9f373681Chris Lattner if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 60860e8862c1fbd3b261da4a64a8c0096f9f373681Chris Lattner unsigned Width = CI->getBitWidth(); 61860e8862c1fbd3b261da4a64a8c0096f9f373681Chris Lattner if (isPowerOf2_32(Width) && Width > 8) { 62860e8862c1fbd3b261da4a64a8c0096f9f373681Chris Lattner // We can handle this value if the recursive binary decomposition is the 636b16eff207f99bbde3c0f7340452a5287218772cTilmann Scheller // same at all levels. 646b16eff207f99bbde3c0f7340452a5287218772cTilmann Scheller APInt Val = CI->getValue(); 652f616bff7ef1e2e08d6d23c2a8b42ec2bfebb173Jim Laskey APInt Val2; 662f616bff7ef1e2e08d6d23c2a8b42ec2bfebb173Jim Laskey while (Val.getBitWidth() != 8) { 672f616bff7ef1e2e08d6d23c2a8b42ec2bfebb173Jim Laskey unsigned NextWidth = Val.getBitWidth()/2; 682f616bff7ef1e2e08d6d23c2a8b42ec2bfebb173Jim Laskey Val2 = Val.lshr(NextWidth); 692f616bff7ef1e2e08d6d23c2a8b42ec2bfebb173Jim Laskey Val2.trunc(Val.getBitWidth()/2); 70860e8862c1fbd3b261da4a64a8c0096f9f373681Chris Lattner Val.trunc(Val.getBitWidth()/2); 71860e8862c1fbd3b261da4a64a8c0096f9f373681Chris Lattner 72860e8862c1fbd3b261da4a64a8c0096f9f373681Chris Lattner // If the top/bottom halves aren't the same, reject it. 734172b10ca1adfc1026428e5f522aaab98bd939adChris Lattner if (Val != Val2) 744172b10ca1adfc1026428e5f522aaab98bd939adChris Lattner return 0; 754172b10ca1adfc1026428e5f522aaab98bd939adChris Lattner } 764172b10ca1adfc1026428e5f522aaab98bd939adChris Lattner return ConstantInt::get(Context, Val); 774172b10ca1adfc1026428e5f522aaab98bd939adChris Lattner } 78ecfe55e65b6a72fddd543c42f2e2df4c96c647baChris Lattner } 79ecfe55e65b6a72fddd543c42f2e2df4c96c647baChris Lattner 80ecfe55e65b6a72fddd543c42f2e2df4c96c647baChris Lattner // Conceptually, we could handle things like: 81ecfe55e65b6a72fddd543c42f2e2df4c96c647baChris Lattner // %a = zext i8 %X to i16 829e4dd9dfc97f3930f58ca6e47bebbd8eb5cdd8a1Nate Begeman // %b = shl i16 %a, 8 83ecfe55e65b6a72fddd543c42f2e2df4c96c647baChris Lattner // %c = or i16 %a, %b 84ecfe55e65b6a72fddd543c42f2e2df4c96c647baChris Lattner // but until there is an example that actually needs this, it doesn't seem 85ecfe55e65b6a72fddd543c42f2e2df4c96c647baChris Lattner // worth worrying about. 86c703a8fbf8653ac8302ae368391a4954c307ca2cChris Lattner return 0; 872a9ddfb903ae3baede7282348afae1f750905248Tilmann Scheller} 88281b55ebeccd3f0d723888c1bb9ec6e476f708f1Chris Lattner 896b16eff207f99bbde3c0f7340452a5287218772cTilmann Schellerstatic int64_t GetOffsetFromIndex(const GetElementPtrInst *GEP, unsigned Idx, 906b16eff207f99bbde3c0f7340452a5287218772cTilmann Scheller bool &VariableIdxFound, TargetData &TD) { 916b16eff207f99bbde3c0f7340452a5287218772cTilmann Scheller // Skip over the first indices. 92c703a8fbf8653ac8302ae368391a4954c307ca2cChris Lattner gep_type_iterator GTI = gep_type_begin(GEP); 93c703a8fbf8653ac8302ae368391a4954c307ca2cChris Lattner for (unsigned i = 1; i != Idx; ++i, ++GTI) 94c703a8fbf8653ac8302ae368391a4954c307ca2cChris Lattner /*skip along*/; 95c703a8fbf8653ac8302ae368391a4954c307ca2cChris Lattner 96c703a8fbf8653ac8302ae368391a4954c307ca2cChris Lattner // Compute the offset implied by the rest of the indices. 97c703a8fbf8653ac8302ae368391a4954c307ca2cChris Lattner int64_t Offset = 0; 982a9ddfb903ae3baede7282348afae1f750905248Tilmann Scheller for (unsigned i = Idx, e = GEP->getNumOperands(); i != e; ++i, ++GTI) { 99c703a8fbf8653ac8302ae368391a4954c307ca2cChris Lattner ConstantInt *OpC = dyn_cast<ConstantInt>(GEP->getOperand(i)); 1009e4dd9dfc97f3930f58ca6e47bebbd8eb5cdd8a1Nate Begeman if (OpC == 0) 1019e4dd9dfc97f3930f58ca6e47bebbd8eb5cdd8a1Nate Begeman return VariableIdxFound = true; 1026d92caddc4aa5fc946b294259e00cc35536e61e8Chris Lattner if (OpC->isZero()) continue; // No offset. 1036d92caddc4aa5fc946b294259e00cc35536e61e8Chris Lattner 1046d92caddc4aa5fc946b294259e00cc35536e61e8Chris Lattner // Handle struct indices, which add their field offset to the pointer. 1056d92caddc4aa5fc946b294259e00cc35536e61e8Chris Lattner if (const StructType *STy = dyn_cast<StructType>(*GTI)) { 1066d92caddc4aa5fc946b294259e00cc35536e61e8Chris Lattner Offset += TD.getStructLayout(STy)->getElementOffset(OpC->getZExtValue()); 107a17b1557ad705c56c41624e6841e19093ed31f21Chris Lattner continue; 108a17b1557ad705c56c41624e6841e19093ed31f21Chris Lattner } 109a17b1557ad705c56c41624e6841e19093ed31f21Chris Lattner 110a17b1557ad705c56c41624e6841e19093ed31f21Chris Lattner // Otherwise, we have a sequential type like an array or vector. Multiply 111a17b1557ad705c56c41624e6841e19093ed31f21Chris Lattner // the index by the ElementSize. 112a17b1557ad705c56c41624e6841e19093ed31f21Chris Lattner uint64_t Size = TD.getTypeAllocSize(GTI.getIndexedType()); 1136d92caddc4aa5fc946b294259e00cc35536e61e8Chris Lattner Offset += Size*OpC->getSExtValue(); 1146d92caddc4aa5fc946b294259e00cc35536e61e8Chris Lattner } 1156d92caddc4aa5fc946b294259e00cc35536e61e8Chris Lattner 1166d92caddc4aa5fc946b294259e00cc35536e61e8Chris Lattner return Offset; 1176d92caddc4aa5fc946b294259e00cc35536e61e8Chris Lattner} 11890564f26d17701e11effa2f4e0fb9a18d8a91274Chris Lattner 11990564f26d17701e11effa2f4e0fb9a18d8a91274Chris Lattner/// IsPointerOffset - Return true if Ptr1 is provably equal to Ptr2 plus a 12090564f26d17701e11effa2f4e0fb9a18d8a91274Chris Lattner/// constant offset, and return that constant offset. For example, Ptr1 might 12190564f26d17701e11effa2f4e0fb9a18d8a91274Chris Lattner/// be &A[42], and Ptr2 might be &A[40]. In this case offset would be -8. 12290564f26d17701e11effa2f4e0fb9a18d8a91274Chris Lattnerstatic bool IsPointerOffset(Value *Ptr1, Value *Ptr2, int64_t &Offset, 12390564f26d17701e11effa2f4e0fb9a18d8a91274Chris Lattner TargetData &TD) { 12490564f26d17701e11effa2f4e0fb9a18d8a91274Chris Lattner // Right now we handle the case when Ptr1/Ptr2 are both GEPs with an identical 125d9989384592a3bd9dd374470a723ca8303071a2dChris Lattner // base. After that base, they may have some number of common (and 126d9989384592a3bd9dd374470a723ca8303071a2dChris Lattner // potentially variable) indices. After that they handle some constant 127d9989384592a3bd9dd374470a723ca8303071a2dChris Lattner // offset, which determines their offset from each other. At this point, we 128d9989384592a3bd9dd374470a723ca8303071a2dChris Lattner // handle no other case. 129d9989384592a3bd9dd374470a723ca8303071a2dChris Lattner GetElementPtrInst *GEP1 = dyn_cast<GetElementPtrInst>(Ptr1); 130d9989384592a3bd9dd374470a723ca8303071a2dChris Lattner GetElementPtrInst *GEP2 = dyn_cast<GetElementPtrInst>(Ptr2); 131d9989384592a3bd9dd374470a723ca8303071a2dChris Lattner if (!GEP1 || !GEP2 || GEP1->getOperand(0) != GEP2->getOperand(0)) 132d9989384592a3bd9dd374470a723ca8303071a2dChris Lattner return false; 133d9989384592a3bd9dd374470a723ca8303071a2dChris Lattner 134d9989384592a3bd9dd374470a723ca8303071a2dChris Lattner // Skip any common indices and track the GEP types. 135d9989384592a3bd9dd374470a723ca8303071a2dChris Lattner unsigned Idx = 1; 136d9989384592a3bd9dd374470a723ca8303071a2dChris Lattner for (; Idx != GEP1->getNumOperands() && Idx != GEP2->getNumOperands(); ++Idx) 1376eaeff29b8a6990107735f7e5f5e49da38f56223Dale Johannesen if (GEP1->getOperand(Idx) != GEP2->getOperand(Idx)) 1386eaeff29b8a6990107735f7e5f5e49da38f56223Dale Johannesen break; 1396eaeff29b8a6990107735f7e5f5e49da38f56223Dale Johannesen 1406eaeff29b8a6990107735f7e5f5e49da38f56223Dale Johannesen bool VariableIdxFound = false; 1416eaeff29b8a6990107735f7e5f5e49da38f56223Dale Johannesen int64_t Offset1 = GetOffsetFromIndex(GEP1, Idx, VariableIdxFound, TD); 1426eaeff29b8a6990107735f7e5f5e49da38f56223Dale Johannesen int64_t Offset2 = GetOffsetFromIndex(GEP2, Idx, VariableIdxFound, TD); 1436eaeff29b8a6990107735f7e5f5e49da38f56223Dale Johannesen if (VariableIdxFound) return false; 1446eaeff29b8a6990107735f7e5f5e49da38f56223Dale Johannesen 1456eaeff29b8a6990107735f7e5f5e49da38f56223Dale Johannesen Offset = Offset2-Offset1; 1466eaeff29b8a6990107735f7e5f5e49da38f56223Dale Johannesen return true; 1476eaeff29b8a6990107735f7e5f5e49da38f56223Dale Johannesen} 1486eaeff29b8a6990107735f7e5f5e49da38f56223Dale Johannesen 1496eaeff29b8a6990107735f7e5f5e49da38f56223Dale Johannesen 1506eaeff29b8a6990107735f7e5f5e49da38f56223Dale Johannesen/// MemsetRange - Represents a range of memset'd bytes with the ByteVal value. 1516eaeff29b8a6990107735f7e5f5e49da38f56223Dale Johannesen/// This allows us to analyze stores like: 1526eaeff29b8a6990107735f7e5f5e49da38f56223Dale Johannesen/// store 0 -> P+1 1536eaeff29b8a6990107735f7e5f5e49da38f56223Dale Johannesen/// store 0 -> P+0 1546eaeff29b8a6990107735f7e5f5e49da38f56223Dale Johannesen/// store 0 -> P+3 1556eaeff29b8a6990107735f7e5f5e49da38f56223Dale Johannesen/// store 0 -> P+2 1566eaeff29b8a6990107735f7e5f5e49da38f56223Dale Johannesen/// which sometimes happens with stores to arrays of structs etc. When we see 1576eaeff29b8a6990107735f7e5f5e49da38f56223Dale Johannesen/// the first store, we make a range [1, 2). The second store extends the range 15854fc97dcdc0ab747f49bd09c5a877bfd2a00e364Evan Cheng/// to [0, 2). The third makes a new range [2, 3). The fourth store joins the 15954fc97dcdc0ab747f49bd09c5a877bfd2a00e364Evan Cheng/// two ranges into [0, 3) which is memset'able. 1608608f2eff2dab5345243c40d0bca9138f2dce6f1Evan Chengnamespace { 16154fc97dcdc0ab747f49bd09c5a877bfd2a00e364Evan Chengstruct MemsetRange { 1628608f2eff2dab5345243c40d0bca9138f2dce6f1Evan Cheng // Start/End - A semi range that describes the span that this range covers. 16354fc97dcdc0ab747f49bd09c5a877bfd2a00e364Evan Cheng // The range is closed at the start and open at the end: [Start, End). 1648608f2eff2dab5345243c40d0bca9138f2dce6f1Evan Cheng int64_t Start, End; 1658608f2eff2dab5345243c40d0bca9138f2dce6f1Evan Cheng 1668608f2eff2dab5345243c40d0bca9138f2dce6f1Evan Cheng /// StartPtr - The getelementptr instruction that points to the start of the 16754fc97dcdc0ab747f49bd09c5a877bfd2a00e364Evan Cheng /// range. 16830e62c098b5841259f8026df1c5c45c7c1182a38Arnold Schwaighofer Value *StartPtr; 16930e62c098b5841259f8026df1c5c45c7c1182a38Arnold Schwaighofer 17030e62c098b5841259f8026df1c5c45c7c1182a38Arnold Schwaighofer /// Alignment - The known alignment of the first store. 17130e62c098b5841259f8026df1c5c45c7c1182a38Arnold Schwaighofer unsigned Alignment; 17230e62c098b5841259f8026df1c5c45c7c1182a38Arnold Schwaighofer 17330e62c098b5841259f8026df1c5c45c7c1182a38Arnold Schwaighofer /// TheStores - The actual stores that make up this range. 174281b55ebeccd3f0d723888c1bb9ec6e476f708f1Chris Lattner SmallVector<StoreInst*, 16> TheStores; 1753c0f9cc90cdcb70caf0dc517b9f9206d731aeb70Chris Lattner 1763c0f9cc90cdcb70caf0dc517b9f9206d731aeb70Chris Lattner bool isProfitableToUseMemset(const TargetData &TD) const; 1773c0f9cc90cdcb70caf0dc517b9f9206d731aeb70Chris Lattner 1783c0f9cc90cdcb70caf0dc517b9f9206d731aeb70Chris Lattner}; 179ddb739e5ea6ccf6fa4f4e2a23e3da550868efaa1Chris Lattner} // end anon namespace 180ddb739e5ea6ccf6fa4f4e2a23e3da550868efaa1Chris Lattner 1819008ca6b6b4f638cfafccb593cbc5b1d3f5ab877Nate Begemanbool MemsetRange::isProfitableToUseMemset(const TargetData &TD) const { 182ddb739e5ea6ccf6fa4f4e2a23e3da550868efaa1Chris Lattner // If we found more than 8 stores to merge or 64 bytes, use memset. 183ddb739e5ea6ccf6fa4f4e2a23e3da550868efaa1Chris Lattner if (TheStores.size() >= 8 || End-Start >= 64) return true; 184ddb739e5ea6ccf6fa4f4e2a23e3da550868efaa1Chris Lattner 1859008ca6b6b4f638cfafccb593cbc5b1d3f5ab877Nate Begeman // Assume that the code generator is capable of merging pairs of stores 186116cc48e30b9c307bf3eec29c890b4ba25cd18dbChris Lattner // together if it wants to. 187116cc48e30b9c307bf3eec29c890b4ba25cd18dbChris Lattner if (TheStores.size() <= 2) return false; 188116cc48e30b9c307bf3eec29c890b4ba25cd18dbChris Lattner 1899008ca6b6b4f638cfafccb593cbc5b1d3f5ab877Nate Begeman // If we have fewer than 8 stores, it can still be worthwhile to do this. 1909008ca6b6b4f638cfafccb593cbc5b1d3f5ab877Nate Begeman // For example, merging 4 i8 stores into an i32 store is useful almost always. 191116cc48e30b9c307bf3eec29c890b4ba25cd18dbChris Lattner // However, merging 2 32-bit stores isn't useful on a 32-bit architecture (the 192116cc48e30b9c307bf3eec29c890b4ba25cd18dbChris Lattner // memset will be split into 2 32-bit stores anyway) and doing so can 193116cc48e30b9c307bf3eec29c890b4ba25cd18dbChris Lattner // pessimize the llvm optimizer. 1949008ca6b6b4f638cfafccb593cbc5b1d3f5ab877Nate Begeman // 1959008ca6b6b4f638cfafccb593cbc5b1d3f5ab877Nate Begeman // Since we don't have perfect knowledge here, make some assumptions: assume 196ddb739e5ea6ccf6fa4f4e2a23e3da550868efaa1Chris Lattner // the maximum GPR width is the same size as the pointer size and assume that 197d0608e191ff9c00af68985f246410c219d1bec57Chris Lattner // this width can be stored. If so, check to see whether we will end up 198d0608e191ff9c00af68985f246410c219d1bec57Chris Lattner // actually reducing the number of stores used. 199f24380e78ecc8a2db1b2116867d878b1e7c6f6edChris Lattner unsigned Bytes = unsigned(End-Start); 200d0608e191ff9c00af68985f246410c219d1bec57Chris Lattner unsigned NumPointerStores = Bytes/TD.getPointerSize(); 2013c0f9cc90cdcb70caf0dc517b9f9206d731aeb70Chris Lattner 2023c0f9cc90cdcb70caf0dc517b9f9206d731aeb70Chris Lattner // Assume the remaining bytes if any are done a byte at a time. 2033c0f9cc90cdcb70caf0dc517b9f9206d731aeb70Chris Lattner unsigned NumByteStores = Bytes - NumPointerStores*TD.getPointerSize(); 2049008ca6b6b4f638cfafccb593cbc5b1d3f5ab877Nate Begeman 2053c0f9cc90cdcb70caf0dc517b9f9206d731aeb70Chris Lattner // If we will reduce the # stores (according to this heuristic), do the 20666ffe6be0c7b50100a00cb0cc87a5d4983818572Evan Cheng // transformation. This encourages merging 4 x i8 -> i32 and 2 x i16 -> i32 20766ffe6be0c7b50100a00cb0cc87a5d4983818572Evan Cheng // etc. 20866ffe6be0c7b50100a00cb0cc87a5d4983818572Evan Cheng return TheStores.size() > NumPointerStores+NumByteStores; 20966ffe6be0c7b50100a00cb0cc87a5d4983818572Evan Cheng} 2103c0f9cc90cdcb70caf0dc517b9f9206d731aeb70Chris Lattner 2113c0f9cc90cdcb70caf0dc517b9f9206d731aeb70Chris Lattner 2127ff7e674580adad7a5bccdbd74cf9c9f05e46d0fChris Lattnernamespace { 21364b3a08bc696b2ef8733d72ce81e49be175cbbffChris Lattnerclass MemsetRanges { 214e87192a854ff0f2f1904dd9ea282eb36059bb5afChris Lattner /// Ranges - A sorted list of the memset ranges. We use std::list here 215140a58f9dfda30dbb80edd3da1b5632c178f7efcChris Lattner /// because each element is relatively large and expensive to copy. 216140a58f9dfda30dbb80edd3da1b5632c178f7efcChris Lattner std::list<MemsetRange> Ranges; 217140a58f9dfda30dbb80edd3da1b5632c178f7efcChris Lattner typedef std::list<MemsetRange>::iterator range_iterator; 218475871a144eb604ddaf37503397ba0941442e5fbDan Gohman TargetData &TD; 2193c0f9cc90cdcb70caf0dc517b9f9206d731aeb70Chris Lattnerpublic: 2200bbea954331b8f08afa5b094dfb0841829c70eaaChris Lattner MemsetRanges(TargetData &td) : TD(td) {} 22121e463b2bf864671a87ebe386cb100ef9349a540Nate Begeman 2227c5a3d390a463fb50a6eee7ae3174817925e6d28Chris Lattner typedef std::list<MemsetRange>::const_iterator const_iterator; 2230111999a88077f237c49d03c5e7891ec874b33a9Nicolas Geoffray const_iterator begin() const { return Ranges.begin(); } 2240111999a88077f237c49d03c5e7891ec874b33a9Nicolas Geoffray const_iterator end() const { return Ranges.end(); } 2250111999a88077f237c49d03c5e7891ec874b33a9Nicolas Geoffray bool empty() const { return Ranges.empty(); } 2260111999a88077f237c49d03c5e7891ec874b33a9Nicolas Geoffray 2270111999a88077f237c49d03c5e7891ec874b33a9Nicolas Geoffray void addStore(int64_t OffsetFromFirst, StoreInst *SI); 2280111999a88077f237c49d03c5e7891ec874b33a9Nicolas Geoffray}; 229331d1bc5dfe1be9090e29f9af9579888a63a9a79Chris Lattner 2307c5a3d390a463fb50a6eee7ae3174817925e6d28Chris Lattner} // end anon namespace 23161e729e2e9517ab2d8887bab86fb377900fa1081Dan Gohman 2327c5a3d390a463fb50a6eee7ae3174817925e6d28Chris Lattner 233da6d20f0c15205923cb2c3ef4bf9b5d77de88881Chris Lattner/// addStore - Add a new store to the MemsetRanges data structure. This adds a 234da6d20f0c15205923cb2c3ef4bf9b5d77de88881Chris Lattner/// new range for the specified store at the specified offset, merging into 235da6d20f0c15205923cb2c3ef4bf9b5d77de88881Chris Lattner/// existing ranges as appropriate. 236fc5b1ab94959879a91c34aee8859e652a50270d0Chris Lattnervoid MemsetRanges::addStore(int64_t Start, StoreInst *SI) { 2375b8f82e35b51bf007de07a7ca9347d804084ddf8Scott Michel int64_t End = Start+TD.getTypeStoreSize(SI->getOperand(0)->getType()); 238825b72b0571821bf2d378749f69d6c4cfb52d2f9Owen Anderson 2395b8f82e35b51bf007de07a7ca9347d804084ddf8Scott Michel // Do a linear search of the ranges to see if this can be joined and/or to 240fc5b1ab94959879a91c34aee8859e652a50270d0Chris Lattner // find the insertion point in the list. We keep the ranges sorted for 241fc5b1ab94959879a91c34aee8859e652a50270d0Chris Lattner // simplicity here. This is a linear search of a linked list, which is ugly, 242fc5b1ab94959879a91c34aee8859e652a50270d0Chris Lattner // however the number of ranges is limited, so this won't get crazy slow. 243475871a144eb604ddaf37503397ba0941442e5fbDan Gohman range_iterator I = Ranges.begin(), E = Ranges.end(); 244475871a144eb604ddaf37503397ba0941442e5fbDan Gohman 245144d8f09e139f691cafadbc17873943ba4c465f3Evan Cheng while (I != E && Start > I->End) 24673e0914848662404cf2aa18eb049ff5aae543388Dan Gohman ++I; 247fc5b1ab94959879a91c34aee8859e652a50270d0Chris Lattner 248fc5b1ab94959879a91c34aee8859e652a50270d0Chris Lattner // We now know that I == E, in which case we didn't find anything to merge 249fc5b1ab94959879a91c34aee8859e652a50270d0Chris Lattner // with, or that Start <= I->End. If End < I->Start or I == E, then we need 250fc5b1ab94959879a91c34aee8859e652a50270d0Chris Lattner // to insert a new range. Handle this now. 251475871a144eb604ddaf37503397ba0941442e5fbDan Gohman if (I == E || End < I->Start) { 25273e0914848662404cf2aa18eb049ff5aae543388Dan Gohman MemsetRange &R = *Ranges.insert(I, MemsetRange()); 253fc5b1ab94959879a91c34aee8859e652a50270d0Chris Lattner R.Start = Start; 254fc5b1ab94959879a91c34aee8859e652a50270d0Chris Lattner R.End = End; 255fc5b1ab94959879a91c34aee8859e652a50270d0Chris Lattner R.StartPtr = SI->getPointerOperand(); 256fc5b1ab94959879a91c34aee8859e652a50270d0Chris Lattner R.Alignment = SI->getAlignment(); 257475871a144eb604ddaf37503397ba0941442e5fbDan Gohman R.TheStores.push_back(SI); 25873e0914848662404cf2aa18eb049ff5aae543388Dan Gohman return; 259fc5b1ab94959879a91c34aee8859e652a50270d0Chris Lattner } 260fc5b1ab94959879a91c34aee8859e652a50270d0Chris Lattner 261fc5b1ab94959879a91c34aee8859e652a50270d0Chris Lattner // This store overlaps with I, add it. 262475871a144eb604ddaf37503397ba0941442e5fbDan Gohman I->TheStores.push_back(SI); 26373e0914848662404cf2aa18eb049ff5aae543388Dan Gohman 264fc5b1ab94959879a91c34aee8859e652a50270d0Chris Lattner // At this point, we may have an interval that completely contains our store. 265fc5b1ab94959879a91c34aee8859e652a50270d0Chris Lattner // If so, just add it to the interval and return. 266fc5b1ab94959879a91c34aee8859e652a50270d0Chris Lattner if (I->Start <= Start && I->End >= End) 267fc5b1ab94959879a91c34aee8859e652a50270d0Chris Lattner return; 268475871a144eb604ddaf37503397ba0941442e5fbDan Gohman 26973e0914848662404cf2aa18eb049ff5aae543388Dan Gohman // Now we know that Start <= I->End and End >= I->Start so the range overlaps 270fc5b1ab94959879a91c34aee8859e652a50270d0Chris Lattner // but is not entirely contained within the range. 271da6d20f0c15205923cb2c3ef4bf9b5d77de88881Chris Lattner 272e4bc9ea0a560d8a0ba42f5a2da617e1f1f834710Chris Lattner // See if the range extends the start of the range. In this case, it couldn't 273e4bc9ea0a560d8a0ba42f5a2da617e1f1f834710Chris Lattner // possibly cause it to join the prior range, because otherwise we would have 274475871a144eb604ddaf37503397ba0941442e5fbDan Gohman // stopped on *it*. 2751f873003266fbdec7c2c48a965c60f4e2e35a158Chris Lattner if (Start < I->Start) { 2761607f05cb7d77d01ce521a30232faa389dbed4e2Duncan Sands I->Start = Start; 2771607f05cb7d77d01ce521a30232faa389dbed4e2Duncan Sands I->StartPtr = SI->getPointerOperand(); 2781607f05cb7d77d01ce521a30232faa389dbed4e2Duncan Sands I->Alignment = SI->getAlignment(); 2791607f05cb7d77d01ce521a30232faa389dbed4e2Duncan Sands } 2801607f05cb7d77d01ce521a30232faa389dbed4e2Duncan Sands 2811607f05cb7d77d01ce521a30232faa389dbed4e2Duncan Sands // Now we know that Start <= I->End and Start >= I->Start (so the startpoint 282475871a144eb604ddaf37503397ba0941442e5fbDan Gohman // is in or right at the end of I), and that End >= I->Start. Extend I out to 283fc5b1ab94959879a91c34aee8859e652a50270d0Chris Lattner // End. 284475871a144eb604ddaf37503397ba0941442e5fbDan Gohman if (End > I->End) { 285977a76fbb6ea1b87dfd7fbbe2ae2afb63e982ff3Dan Gohman I->End = End; 286fd29e0eb060ea8b4d490860329234d2ae5f5952eDan Gohman range_iterator NextI = I; 287fd29e0eb060ea8b4d490860329234d2ae5f5952eDan Gohman while (++NextI != E && End >= NextI->Start) { 288ea859be53ca13a1547c4675549946b74dc3c6f41Dan Gohman // Merge the range in. 289bbe77de450ef36b4f83cc3b57705a9758adbd925Chris Lattner I->TheStores.append(NextI->TheStores.begin(), NextI->TheStores.end()); 2904a95945fa5aa431110f50092f4a45d24772a553bNate Begeman if (NextI->End > I->End) 291ff9b373e8f5006c629af81e2619778b4c4f5249eEvan Cheng I->End = NextI->End; 2921fdbc1dd4e9cb42c79a30e8dc308c322e923cc52Dan Gohman Ranges.erase(NextI); 293bdab93a2ef5d9574bb4e322e020849f9bc9c90d7Dale Johannesen NextI = I; 294bdab93a2ef5d9574bb4e322e020849f9bc9c90d7Dale Johannesen } 2951fdbc1dd4e9cb42c79a30e8dc308c322e923cc52Dan Gohman } 29697efa365869d3b7b62836434585360a232836f0eDale Johannesen} 29797efa365869d3b7b62836434585360a232836f0eDale Johannesen 2981fdbc1dd4e9cb42c79a30e8dc308c322e923cc52Dan Gohman//===----------------------------------------------------------------------===// 299ddc787dfdc75fb2d78eb3e5793ca0f417ad74fd3Chris Lattner// MemCpyOpt Pass 3004234f57fa02b1f04a9f52a7b3c2aa22d32ac521cChris Lattner//===----------------------------------------------------------------------===// 301331d1bc5dfe1be9090e29f9af9579888a63a9a79Chris Lattner 302331d1bc5dfe1be9090e29f9af9579888a63a9a79Chris Lattnernamespace { 303e50ed30282bb5b4a9ed952580523f2dda16215acOwen Anderson class MemCpyOpt : public FunctionPass { 304c4c6257c1a154279bf10e9498d46d6c1793dbaa7Evan Cheng bool runOnFunction(Function &F); 30528d08fdb9f6572cafd5aae95c7caffa3cd136d8eDale Johannesen public: 30628d08fdb9f6572cafd5aae95c7caffa3cd136d8eDale Johannesen static char ID; // Pass identification, replacement for typeid 30728d08fdb9f6572cafd5aae95c7caffa3cd136d8eDale Johannesen MemCpyOpt() : FunctionPass(&ID) {} 30828d08fdb9f6572cafd5aae95c7caffa3cd136d8eDale Johannesen 30928d08fdb9f6572cafd5aae95c7caffa3cd136d8eDale Johannesen private: 31048884cd80b52be1528618f2e9b3425ac24e7b5caChris Lattner // This transformation requires dominator postdominator info 311da43bcf624acb56a3d77bb5ae9a02728af032613Evan Cheng virtual void getAnalysisUsage(AnalysisUsage &AU) const { 312da43bcf624acb56a3d77bb5ae9a02728af032613Evan Cheng AU.setPreservesCFG(); 313da43bcf624acb56a3d77bb5ae9a02728af032613Evan Cheng AU.addRequired<DominatorTree>(); 314475871a144eb604ddaf37503397ba0941442e5fbDan Gohman AU.addRequired<MemoryDependenceAnalysis>(); 31548884cd80b52be1528618f2e9b3425ac24e7b5caChris Lattner AU.addRequired<AliasAnalysis>(); 316da43bcf624acb56a3d77bb5ae9a02728af032613Evan Cheng AU.addPreserved<AliasAnalysis>(); 317475871a144eb604ddaf37503397ba0941442e5fbDan Gohman AU.addPreserved<MemoryDependenceAnalysis>(); 3185e764233f398b6929b67701672a5e78fec20ce2eChris Lattner } 31948884cd80b52be1528618f2e9b3425ac24e7b5caChris Lattner 320c9addb74883fef318140272768422656a694341fChris Lattner // Helper fuctions 321c9addb74883fef318140272768422656a694341fChris Lattner bool processStore(StoreInst *SI, BasicBlock::iterator &BBI); 322c9addb74883fef318140272768422656a694341fChris Lattner bool processMemCpy(MemCpyInst *M); 323c9addb74883fef318140272768422656a694341fChris Lattner bool processMemMove(MemMoveInst *M); 324c4c6257c1a154279bf10e9498d46d6c1793dbaa7Evan Cheng bool performCallSlotOptzn(MemCpyInst *cpy, CallInst *C); 325861939152debbaa15a55a196a4321837c7bc379dEvan Cheng bool iterateOnFunction(Function &F); 326861939152debbaa15a55a196a4321837c7bc379dEvan Cheng }; 327861939152debbaa15a55a196a4321837c7bc379dEvan Cheng 328861939152debbaa15a55a196a4321837c7bc379dEvan Cheng char MemCpyOpt::ID = 0; 329861939152debbaa15a55a196a4321837c7bc379dEvan Cheng} 330861939152debbaa15a55a196a4321837c7bc379dEvan Cheng 331861939152debbaa15a55a196a4321837c7bc379dEvan Cheng// createMemCpyOptPass - The public interface to this file... 33243c6e7cd9b0d9a3b0006650ddfac256848f10d51Nicolas GeoffrayFunctionPass *llvm::createMemCpyOptPass() { return new MemCpyOpt(); } 33398ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman 33498ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohmanstatic RegisterPass<MemCpyOpt> X("memcpyopt", 33565c3c8f323198b99b88b109654194540cf9b3fa5Sandeep Patel "MemCpy Optimization"); 33698ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman 33798ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman 33898ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman 33930e62c098b5841259f8026df1c5c45c7c1182a38Arnold Schwaighofer/// processStore - When GVN is scanning forward over instructions, we look for 34054aeea39a743effe88eedb43d2f7f4805e806ab5Dan Gohman/// some other patterns to fold away. In particular, this looks for stores to 341ffd0200abfd63177257f949a3674b91dcf87bf23Tilmann Scheller/// neighboring locations of memory. If it sees enough consequtive ones 342e50ed30282bb5b4a9ed952580523f2dda16215acOwen Anderson/// (currently 4) it attempts to merge them together into a memcpy/memset. 343ffd0200abfd63177257f949a3674b91dcf87bf23Tilmann Schellerbool MemCpyOpt::processStore(StoreInst *SI, BasicBlock::iterator &BBI) { 344ffd0200abfd63177257f949a3674b91dcf87bf23Tilmann Scheller if (SI->isVolatile()) return false; 34554aeea39a743effe88eedb43d2f7f4805e806ab5Dan Gohman 346b4202b84d7e54efe5e144885c7da63e6cc465f80Bill Wendling LLVMContext &Context = SI->getContext(); 34720c568f366be211323eeaf0e45ef053278ec9ddcBill Wendling 34820c568f366be211323eeaf0e45ef053278ec9ddcBill Wendling // There are two cases that are interesting for this code to handle: memcpy 34954fc97dcdc0ab747f49bd09c5a877bfd2a00e364Evan Cheng // and memset. Right now we only handle memset. 350475871a144eb604ddaf37503397ba0941442e5fbDan Gohman 351475871a144eb604ddaf37503397ba0941442e5fbDan Gohman // Ensure that the value being stored is something that can be memset'able a 35230e62c098b5841259f8026df1c5c45c7c1182a38Arnold Schwaighofer // byte at a time like "0" or "-1" or any width, as well as things like 353475871a144eb604ddaf37503397ba0941442e5fbDan Gohman // 0xA0A0A0A0 and 0.0. 35433c960f523f2308482d5b2816af46a7ec90a6d3dDale Johannesen Value *ByteVal = isBytewiseValue(SI->getOperand(0)); 35533c960f523f2308482d5b2816af46a7ec90a6d3dDale Johannesen if (!ByteVal) 35633c960f523f2308482d5b2816af46a7ec90a6d3dDale Johannesen return false; 35733c960f523f2308482d5b2816af46a7ec90a6d3dDale Johannesen 3582a9ddfb903ae3baede7282348afae1f750905248Tilmann Scheller TargetData *TD = getAnalysisIfAvailable<TargetData>(); 35933c960f523f2308482d5b2816af46a7ec90a6d3dDale Johannesen if (!TD) return false; 360475871a144eb604ddaf37503397ba0941442e5fbDan Gohman AliasAnalysis &AA = getAnalysis<AliasAnalysis>(); 361475871a144eb604ddaf37503397ba0941442e5fbDan Gohman Module *M = SI->getParent()->getParent()->getParent(); 362475871a144eb604ddaf37503397ba0941442e5fbDan Gohman 363475871a144eb604ddaf37503397ba0941442e5fbDan Gohman // Okay, so we now have a single store that can be splatable. Scan to find 364475871a144eb604ddaf37503397ba0941442e5fbDan Gohman // all subsequent stores of the same value to offset from the same pointer. 365475871a144eb604ddaf37503397ba0941442e5fbDan Gohman // Join these together into ranges, so we can decide whether contiguous blocks 366475871a144eb604ddaf37503397ba0941442e5fbDan Gohman // are stored. 367475871a144eb604ddaf37503397ba0941442e5fbDan Gohman MemsetRanges Ranges(*TD); 3687795932d41a84c921a5d348b7fa70f5d32e146d0Bill Wendling 369475871a144eb604ddaf37503397ba0941442e5fbDan Gohman Value *StartPtr = SI->getPointerOperand(); 3705b3b695c2f1e11b6f5e0c89e1644211a92edab49Dale Johannesen 3715b3b695c2f1e11b6f5e0c89e1644211a92edab49Dale Johannesen BasicBlock::iterator BI = SI; 3725b3b695c2f1e11b6f5e0c89e1644211a92edab49Dale Johannesen for (++BI; !isa<TerminatorInst>(BI); ++BI) { 373475871a144eb604ddaf37503397ba0941442e5fbDan Gohman if (isa<CallInst>(BI) || isa<InvokeInst>(BI)) { 3745b3b695c2f1e11b6f5e0c89e1644211a92edab49Dale Johannesen // If the call is readnone, ignore it, otherwise bail out. We don't even 3755b3b695c2f1e11b6f5e0c89e1644211a92edab49Dale Johannesen // allow readonly here because we don't want something like: 376475871a144eb604ddaf37503397ba0941442e5fbDan Gohman // A[1] = 2; strlen(A); A[2] = 2; -> memcpy(A, ...); strlen(A). 3775b3b695c2f1e11b6f5e0c89e1644211a92edab49Dale Johannesen if (AA.getModRefBehavior(CallSite::get(BI)) == 378475871a144eb604ddaf37503397ba0941442e5fbDan Gohman AliasAnalysis::DoesNotAccessMemory) 3795b3b695c2f1e11b6f5e0c89e1644211a92edab49Dale Johannesen continue; 380475871a144eb604ddaf37503397ba0941442e5fbDan Gohman 3814c9369df57a52cec5e1fc735e61a979766288074Dale Johannesen // TODO: If this is a memset, try to join it in. 382475871a144eb604ddaf37503397ba0941442e5fbDan Gohman 383475871a144eb604ddaf37503397ba0941442e5fbDan Gohman break; 384475871a144eb604ddaf37503397ba0941442e5fbDan Gohman } else if (isa<VAArgInst>(BI) || isa<LoadInst>(BI)) 385475871a144eb604ddaf37503397ba0941442e5fbDan Gohman break; 386475871a144eb604ddaf37503397ba0941442e5fbDan Gohman 387475871a144eb604ddaf37503397ba0941442e5fbDan Gohman // If this is a non-store instruction it is fine, ignore it. 388475871a144eb604ddaf37503397ba0941442e5fbDan Gohman StoreInst *NextStore = dyn_cast<StoreInst>(BI); 389475871a144eb604ddaf37503397ba0941442e5fbDan Gohman if (NextStore == 0) continue; 390475871a144eb604ddaf37503397ba0941442e5fbDan Gohman 391475871a144eb604ddaf37503397ba0941442e5fbDan Gohman // If this is a store, see if we can merge it in. 39298ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman if (NextStore->isVolatile()) break; 39398ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman 39465c3c8f323198b99b88b109654194540cf9b3fa5Sandeep Patel // Check to see if this stored value is of the same byte-splattable value. 39598ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman if (ByteVal != isBytewiseValue(NextStore->getOperand(0))) 39698ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman break; 39798ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman 39865c3c8f323198b99b88b109654194540cf9b3fa5Sandeep Patel // Check to see if this store is to a constant offset from the start ptr. 39998ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman int64_t Offset; 40098ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman if (!IsPointerOffset(StartPtr, NextStore->getPointerOperand(), Offset, *TD)) 40198ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman break; 40298ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman 40398ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman Ranges.addStore(Offset, NextStore); 40498ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman } 40598ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman 40698ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman // If we have no ranges, then we just had a single store with nothing that 40798ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman // could be merged in. This is a very common case of course. 40898ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman if (Ranges.empty()) 40998ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman return false; 41098ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman 41165c3c8f323198b99b88b109654194540cf9b3fa5Sandeep Patel // If we had at least one store that could be merged in, add the starting 41298ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman // store as well. We try to avoid this unless there is at least something 41398ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman // interesting as a small compile-time optimization. 41498ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman Ranges.addStore(0, SI); 41598ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman 41698ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman Function *MemSetF = 0; 41798ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman 41865c3c8f323198b99b88b109654194540cf9b3fa5Sandeep Patel // Now that we have full information about ranges, loop over the ranges and 41998ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman // emit memset's for anything big enough to be worthwhile. 42098ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman bool MadeChange = false; 42198ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman for (MemsetRanges::const_iterator I = Ranges.begin(), E = Ranges.end(); 42298ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman I != E; ++I) { 42398ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman const MemsetRange &Range = *I; 42498ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman 42598ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman if (Range.TheStores.size() == 1) continue; 42665c3c8f323198b99b88b109654194540cf9b3fa5Sandeep Patel 42798ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman // If it is profitable to lower this range to memset, do so now. 42898ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman if (!Range.isProfitableToUseMemset(*TD)) 42998ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman continue; 43098ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman 43198ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman // Otherwise, we do want to transform this! Create a new memset. We put 43265c3c8f323198b99b88b109654194540cf9b3fa5Sandeep Patel // the memset right before the first instruction that isn't part of this 43398ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman // memset block. This ensure that the memset is dominated by any addressing 43498ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman // instruction needed by the start of the block. 43598ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman BasicBlock::iterator InsertPt = BI; 43698ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman 43798ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman if (MemSetF == 0) { 43865c3c8f323198b99b88b109654194540cf9b3fa5Sandeep Patel const Type *Ty = Type::getInt64Ty(Context); 43998ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman MemSetF = Intrinsic::getDeclaration(M, Intrinsic::memset, &Ty, 1); 44098ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman } 44198ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman 44298ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman // Get the starting pointer of the block. 44398ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman StartPtr = Range.StartPtr; 44498ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman 44565c3c8f323198b99b88b109654194540cf9b3fa5Sandeep Patel // Cast the start ptr to be i8* as memset requires. 44698ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman const Type *i8Ptr = Type::getInt8PtrTy(Context); 44798ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman if (StartPtr->getType() != i8Ptr) 44898ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman StartPtr = new BitCastInst(StartPtr, i8Ptr, StartPtr->getName(), 44998ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman InsertPt); 45098ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman 45198ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman Value *Ops[] = { 45265c3c8f323198b99b88b109654194540cf9b3fa5Sandeep Patel StartPtr, ByteVal, // Start, value 45398ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman // size 45498ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman ConstantInt::get(Type::getInt64Ty(Context), Range.End-Range.Start), 45598ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman // align 45698ca4f2a325f72374a477f9deba7d09e8999c29bDan Gohman ConstantInt::get(Type::getInt32Ty(Context), Range.Alignment) 4577c5a3d390a463fb50a6eee7ae3174817925e6d28Chris Lattner }; 4587c5a3d390a463fb50a6eee7ae3174817925e6d28Chris Lattner Value *C = CallInst::Create(MemSetF, Ops, Ops+4, "", InsertPt); 4597c5a3d390a463fb50a6eee7ae3174817925e6d28Chris Lattner DEBUG(errs() << "Replace stores:\n"; 4607c5a3d390a463fb50a6eee7ae3174817925e6d28Chris Lattner for (unsigned i = 0, e = Range.TheStores.size(); i != e; ++i) 461 errs() << *Range.TheStores[i]; 462 errs() << "With: " << *C); C=C; 463 464 // Don't invalidate the iterator 465 BBI = BI; 466 467 // Zap all the stores. 468 for (SmallVector<StoreInst*, 16>::const_iterator 469 SI = Range.TheStores.begin(), 470 SE = Range.TheStores.end(); SI != SE; ++SI) 471 (*SI)->eraseFromParent(); 472 ++NumMemSetInfer; 473 MadeChange = true; 474 } 475 476 return MadeChange; 477} 478 479 480/// performCallSlotOptzn - takes a memcpy and a call that it depends on, 481/// and checks for the possibility of a call slot optimization by having 482/// the call write its result directly into the destination of the memcpy. 483bool MemCpyOpt::performCallSlotOptzn(MemCpyInst *cpy, CallInst *C) { 484 // The general transformation to keep in mind is 485 // 486 // call @func(..., src, ...) 487 // memcpy(dest, src, ...) 488 // 489 // -> 490 // 491 // memcpy(dest, src, ...) 492 // call @func(..., dest, ...) 493 // 494 // Since moving the memcpy is technically awkward, we additionally check that 495 // src only holds uninitialized values at the moment of the call, meaning that 496 // the memcpy can be discarded rather than moved. 497 498 // Deliberately get the source and destination with bitcasts stripped away, 499 // because we'll need to do type comparisons based on the underlying type. 500 Value *cpyDest = cpy->getDest(); 501 Value *cpySrc = cpy->getSource(); 502 CallSite CS = CallSite::get(C); 503 504 // We need to be able to reason about the size of the memcpy, so we require 505 // that it be a constant. 506 ConstantInt *cpyLength = dyn_cast<ConstantInt>(cpy->getLength()); 507 if (!cpyLength) 508 return false; 509 510 // Require that src be an alloca. This simplifies the reasoning considerably. 511 AllocaInst *srcAlloca = dyn_cast<AllocaInst>(cpySrc); 512 if (!srcAlloca) 513 return false; 514 515 // Check that all of src is copied to dest. 516 TargetData *TD = getAnalysisIfAvailable<TargetData>(); 517 if (!TD) return false; 518 519 ConstantInt *srcArraySize = dyn_cast<ConstantInt>(srcAlloca->getArraySize()); 520 if (!srcArraySize) 521 return false; 522 523 uint64_t srcSize = TD->getTypeAllocSize(srcAlloca->getAllocatedType()) * 524 srcArraySize->getZExtValue(); 525 526 if (cpyLength->getZExtValue() < srcSize) 527 return false; 528 529 // Check that accessing the first srcSize bytes of dest will not cause a 530 // trap. Otherwise the transform is invalid since it might cause a trap 531 // to occur earlier than it otherwise would. 532 if (AllocaInst *A = dyn_cast<AllocaInst>(cpyDest)) { 533 // The destination is an alloca. Check it is larger than srcSize. 534 ConstantInt *destArraySize = dyn_cast<ConstantInt>(A->getArraySize()); 535 if (!destArraySize) 536 return false; 537 538 uint64_t destSize = TD->getTypeAllocSize(A->getAllocatedType()) * 539 destArraySize->getZExtValue(); 540 541 if (destSize < srcSize) 542 return false; 543 } else if (Argument *A = dyn_cast<Argument>(cpyDest)) { 544 // If the destination is an sret parameter then only accesses that are 545 // outside of the returned struct type can trap. 546 if (!A->hasStructRetAttr()) 547 return false; 548 549 const Type *StructTy = cast<PointerType>(A->getType())->getElementType(); 550 uint64_t destSize = TD->getTypeAllocSize(StructTy); 551 552 if (destSize < srcSize) 553 return false; 554 } else { 555 return false; 556 } 557 558 // Check that src is not accessed except via the call and the memcpy. This 559 // guarantees that it holds only undefined values when passed in (so the final 560 // memcpy can be dropped), that it is not read or written between the call and 561 // the memcpy, and that writing beyond the end of it is undefined. 562 SmallVector<User*, 8> srcUseList(srcAlloca->use_begin(), 563 srcAlloca->use_end()); 564 while (!srcUseList.empty()) { 565 User *UI = srcUseList.back(); 566 srcUseList.pop_back(); 567 568 if (isa<BitCastInst>(UI)) { 569 for (User::use_iterator I = UI->use_begin(), E = UI->use_end(); 570 I != E; ++I) 571 srcUseList.push_back(*I); 572 } else if (GetElementPtrInst *G = dyn_cast<GetElementPtrInst>(UI)) { 573 if (G->hasAllZeroIndices()) 574 for (User::use_iterator I = UI->use_begin(), E = UI->use_end(); 575 I != E; ++I) 576 srcUseList.push_back(*I); 577 else 578 return false; 579 } else if (UI != C && UI != cpy) { 580 return false; 581 } 582 } 583 584 // Since we're changing the parameter to the callsite, we need to make sure 585 // that what would be the new parameter dominates the callsite. 586 DominatorTree &DT = getAnalysis<DominatorTree>(); 587 if (Instruction *cpyDestInst = dyn_cast<Instruction>(cpyDest)) 588 if (!DT.dominates(cpyDestInst, C)) 589 return false; 590 591 // In addition to knowing that the call does not access src in some 592 // unexpected manner, for example via a global, which we deduce from 593 // the use analysis, we also need to know that it does not sneakily 594 // access dest. We rely on AA to figure this out for us. 595 AliasAnalysis &AA = getAnalysis<AliasAnalysis>(); 596 if (AA.getModRefInfo(C, cpy->getRawDest(), srcSize) != 597 AliasAnalysis::NoModRef) 598 return false; 599 600 // All the checks have passed, so do the transformation. 601 bool changedArgument = false; 602 for (unsigned i = 0; i < CS.arg_size(); ++i) 603 if (CS.getArgument(i)->stripPointerCasts() == cpySrc) { 604 if (cpySrc->getType() != cpyDest->getType()) 605 cpyDest = CastInst::CreatePointerCast(cpyDest, cpySrc->getType(), 606 cpyDest->getName(), C); 607 changedArgument = true; 608 if (CS.getArgument(i)->getType() == cpyDest->getType()) 609 CS.setArgument(i, cpyDest); 610 else 611 CS.setArgument(i, CastInst::CreatePointerCast(cpyDest, 612 CS.getArgument(i)->getType(), cpyDest->getName(), C)); 613 } 614 615 if (!changedArgument) 616 return false; 617 618 // Drop any cached information about the call, because we may have changed 619 // its dependence information by changing its parameter. 620 MemoryDependenceAnalysis &MD = getAnalysis<MemoryDependenceAnalysis>(); 621 MD.removeInstruction(C); 622 623 // Remove the memcpy 624 MD.removeInstruction(cpy); 625 cpy->eraseFromParent(); 626 NumMemCpyInstr++; 627 628 return true; 629} 630 631/// processMemCpy - perform simplication of memcpy's. If we have memcpy A which 632/// copies X to Y, and memcpy B which copies Y to Z, then we can rewrite B to be 633/// a memcpy from X to Z (or potentially a memmove, depending on circumstances). 634/// This allows later passes to remove the first memcpy altogether. 635bool MemCpyOpt::processMemCpy(MemCpyInst *M) { 636 MemoryDependenceAnalysis &MD = getAnalysis<MemoryDependenceAnalysis>(); 637 638 // The are two possible optimizations we can do for memcpy: 639 // a) memcpy-memcpy xform which exposes redundance for DSE. 640 // b) call-memcpy xform for return slot optimization. 641 MemDepResult dep = MD.getDependency(M); 642 if (!dep.isClobber()) 643 return false; 644 if (!isa<MemCpyInst>(dep.getInst())) { 645 if (CallInst *C = dyn_cast<CallInst>(dep.getInst())) 646 return performCallSlotOptzn(M, C); 647 return false; 648 } 649 650 MemCpyInst *MDep = cast<MemCpyInst>(dep.getInst()); 651 652 // We can only transforms memcpy's where the dest of one is the source of the 653 // other 654 if (M->getSource() != MDep->getDest()) 655 return false; 656 657 // Second, the length of the memcpy's must be the same, or the preceeding one 658 // must be larger than the following one. 659 ConstantInt *C1 = dyn_cast<ConstantInt>(MDep->getLength()); 660 ConstantInt *C2 = dyn_cast<ConstantInt>(M->getLength()); 661 if (!C1 || !C2) 662 return false; 663 664 uint64_t DepSize = C1->getValue().getZExtValue(); 665 uint64_t CpySize = C2->getValue().getZExtValue(); 666 667 if (DepSize < CpySize) 668 return false; 669 670 // Finally, we have to make sure that the dest of the second does not 671 // alias the source of the first 672 AliasAnalysis &AA = getAnalysis<AliasAnalysis>(); 673 if (AA.alias(M->getRawDest(), CpySize, MDep->getRawSource(), DepSize) != 674 AliasAnalysis::NoAlias) 675 return false; 676 else if (AA.alias(M->getRawDest(), CpySize, M->getRawSource(), CpySize) != 677 AliasAnalysis::NoAlias) 678 return false; 679 else if (AA.alias(MDep->getRawDest(), DepSize, MDep->getRawSource(), DepSize) 680 != AliasAnalysis::NoAlias) 681 return false; 682 683 // If all checks passed, then we can transform these memcpy's 684 const Type *Ty = M->getLength()->getType(); 685 Function *MemCpyFun = Intrinsic::getDeclaration( 686 M->getParent()->getParent()->getParent(), 687 M->getIntrinsicID(), &Ty, 1); 688 689 Value *Args[4] = { 690 M->getRawDest(), MDep->getRawSource(), M->getLength(), M->getAlignmentCst() 691 }; 692 693 CallInst *C = CallInst::Create(MemCpyFun, Args, Args+4, "", M); 694 695 696 // If C and M don't interfere, then this is a valid transformation. If they 697 // did, this would mean that the two sources overlap, which would be bad. 698 if (MD.getDependency(C) == dep) { 699 MD.removeInstruction(M); 700 M->eraseFromParent(); 701 NumMemCpyInstr++; 702 return true; 703 } 704 705 // Otherwise, there was no point in doing this, so we remove the call we 706 // inserted and act like nothing happened. 707 MD.removeInstruction(C); 708 C->eraseFromParent(); 709 return false; 710} 711 712/// processMemMove - Transforms memmove calls to memcpy calls when the src/dst 713/// are guaranteed not to alias. 714bool MemCpyOpt::processMemMove(MemMoveInst *M) { 715 AliasAnalysis &AA = getAnalysis<AliasAnalysis>(); 716 717 // If the memmove is a constant size, use it for the alias query, this allows 718 // us to optimize things like: memmove(P, P+64, 64); 719 uint64_t MemMoveSize = ~0ULL; 720 if (ConstantInt *Len = dyn_cast<ConstantInt>(M->getLength())) 721 MemMoveSize = Len->getZExtValue(); 722 723 // See if the pointers alias. 724 if (AA.alias(M->getRawDest(), MemMoveSize, M->getRawSource(), MemMoveSize) != 725 AliasAnalysis::NoAlias) 726 return false; 727 728 DEBUG(errs() << "MemCpyOpt: Optimizing memmove -> memcpy: " << *M << "\n"); 729 730 // If not, then we know we can transform this. 731 Module *Mod = M->getParent()->getParent()->getParent(); 732 const Type *Ty = M->getLength()->getType(); 733 M->setOperand(0, Intrinsic::getDeclaration(Mod, Intrinsic::memcpy, &Ty, 1)); 734 735 // MemDep may have over conservative information about this instruction, just 736 // conservatively flush it from the cache. 737 getAnalysis<MemoryDependenceAnalysis>().removeInstruction(M); 738 739 ++NumMoveToCpy; 740 return true; 741} 742 743 744// MemCpyOpt::iterateOnFunction - Executes one iteration of GVN. 745bool MemCpyOpt::iterateOnFunction(Function &F) { 746 bool MadeChange = false; 747 748 // Walk all instruction in the function. 749 for (Function::iterator BB = F.begin(), BBE = F.end(); BB != BBE; ++BB) { 750 for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); 751 BI != BE;) { 752 // Avoid invalidating the iterator. 753 Instruction *I = BI++; 754 755 if (StoreInst *SI = dyn_cast<StoreInst>(I)) 756 MadeChange |= processStore(SI, BI); 757 else if (MemCpyInst *M = dyn_cast<MemCpyInst>(I)) 758 MadeChange |= processMemCpy(M); 759 else if (MemMoveInst *M = dyn_cast<MemMoveInst>(I)) { 760 if (processMemMove(M)) { 761 --BI; // Reprocess the new memcpy. 762 MadeChange = true; 763 } 764 } 765 } 766 } 767 768 return MadeChange; 769} 770 771// MemCpyOpt::runOnFunction - This is the main transformation entry point for a 772// function. 773// 774bool MemCpyOpt::runOnFunction(Function &F) { 775 bool MadeChange = false; 776 while (1) { 777 if (!iterateOnFunction(F)) 778 break; 779 MadeChange = true; 780 } 781 782 return MadeChange; 783} 784 785 786 787