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Implement ReinterpretArray #23750
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Implement ReinterpretArray #23750
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365 changes: 365 additions & 0 deletions
365
deps/patches/llvm-D37939-Mem2Reg-Also-handle-memcpy.patch
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,365 @@ | ||
| From da4504b2d3c6629fbd58634bf76f1b85939d07cf Mon Sep 17 00:00:00 2001 | ||
| From: Keno Fischer <keno@juliacomputing.com> | ||
| Date: Fri, 15 Sep 2017 18:30:59 -0400 | ||
| Subject: [PATCH] [Mem2Reg] Also handle memcpy | ||
|
|
||
| Summary: | ||
| In julia, when we know we're moving data between two memory locations, | ||
| we always emit that as a memcpy rather than a load/store pair. However, | ||
| this can give worse optimization results in certain cases because some | ||
| optimizations that can handle load/store pairs cannot handle memcpys. | ||
| Mem2reg is one of these optimizations. This patch adds rudamentary | ||
| support for mem2reg for recognizing memcpys that cover the whole alloca | ||
| we're promoting. While several more sophisticated passes (SROA, GVN) | ||
| can get similar optimizations, it is preferable to have these kinds | ||
| of cases caught early to expose optimization opportunities before | ||
| getting to these later passes. The approach taken here is to split | ||
| the memcpy into a load/store pair early (after legality analysis) | ||
| and retain the rest of the analysis only on loads/stores. It would | ||
| be possible of course to leave the memcpy as is and generate the | ||
| left over load or store only on demand. However, that would entail | ||
| a significantly larger patch for unclear benefit. | ||
|
|
||
| Reviewers: chandlerc, dberlin | ||
|
|
||
| Subscribers: llvm-commits | ||
|
|
||
| Differential Revision: https://reviews.llvm.org/D37939 | ||
| --- | ||
| lib/Transforms/Utils/PromoteMemoryToRegister.cpp | 166 ++++++++++++++++++++--- | ||
| test/Transforms/Mem2Reg/memcpy.ll | 101 ++++++++++++++ | ||
| 2 files changed, 251 insertions(+), 16 deletions(-) | ||
| create mode 100644 test/Transforms/Mem2Reg/memcpy.ll | ||
|
|
||
| diff --git a/lib/Transforms/Utils/PromoteMemoryToRegister.cpp b/lib/Transforms/Utils/PromoteMemoryToRegister.cpp | ||
| index ac28f59..b08a0a1 100644 | ||
| --- a/lib/Transforms/Utils/PromoteMemoryToRegister.cpp | ||
| +++ b/lib/Transforms/Utils/PromoteMemoryToRegister.cpp | ||
| @@ -49,6 +49,58 @@ STATISTIC(NumSingleStore, "Number of alloca's promoted with a single store"); | ||
| STATISTIC(NumDeadAlloca, "Number of dead alloca's removed"); | ||
| STATISTIC(NumPHIInsert, "Number of PHI nodes inserted"); | ||
|
|
||
| +static bool isSplittableMemCpy(const MemCpyInst *MCI, const AllocaInst *AI) { | ||
| + // Punt if this alloca is an array allocation | ||
| + if (AI->isArrayAllocation()) | ||
| + return false; | ||
| + if (MCI->isVolatile()) | ||
| + return false; | ||
| + Value *Length = MCI->getLength(); | ||
| + if (!isa<ConstantInt>(Length)) | ||
| + return false; | ||
| + // Anything less than the full alloca, we leave for SROA | ||
| + const DataLayout &DL = AI->getModule()->getDataLayout(); | ||
| + size_t AIElSize = DL.getTypeAllocSize(AI->getAllocatedType()); | ||
| + if (cast<ConstantInt>(Length)->getZExtValue() != AIElSize) | ||
| + return false; | ||
| + // If the other argument is also an alloca, we need to be sure that either | ||
| + // the types are bitcastable, or the other alloca is not eligible for | ||
| + // promotion (e.g. because the memcpy is for less than the whole size of | ||
| + // that alloca), otherwise we risk turning an allocatable alloca into a | ||
| + // non-allocatable one when splitting the memcpy. | ||
| + AllocaInst *OtherAI = dyn_cast<AllocaInst>( | ||
| + AI == MCI->getSource() ? MCI->getDest() : MCI->getSource()); | ||
| + if (OtherAI) { | ||
| + if (!CastInst::isBitCastable(AI->getAllocatedType(), | ||
| + OtherAI->getAllocatedType()) && | ||
| + DL.getTypeAllocSize(OtherAI->getAllocatedType()) == AIElSize) | ||
| + return false; | ||
| + } | ||
| + return true; | ||
| +} | ||
| + | ||
| +/// Look at the result of a bitcast and see if it's only used by lifetime | ||
| +/// intrinsics or splittable memcpys. This is needed, because IRBuilder | ||
| +/// will always insert a bitcast to i8* for these intrinsics. | ||
| +static bool onlyHasCanonicalizableUsers(const AllocaInst *AI, const Value *V) { | ||
| + for (const User *U : V->users()) { | ||
| + const IntrinsicInst *II = dyn_cast<IntrinsicInst>(U); | ||
| + if (!II) | ||
| + return false; | ||
| + | ||
| + if (isa<MemCpyInst>(II)) { | ||
| + if (!isSplittableMemCpy(cast<MemCpyInst>(II), AI)) | ||
| + return false; | ||
| + continue; | ||
| + } | ||
| + | ||
| + if (II->getIntrinsicID() != Intrinsic::lifetime_start && | ||
| + II->getIntrinsicID() != Intrinsic::lifetime_end) | ||
| + return false; | ||
| + } | ||
| + return true; | ||
| +} | ||
| + | ||
| bool llvm::isAllocaPromotable(const AllocaInst *AI) { | ||
| // FIXME: If the memory unit is of pointer or integer type, we can permit | ||
| // assignments to subsections of the memory unit. | ||
| @@ -68,6 +120,9 @@ bool llvm::isAllocaPromotable(const AllocaInst *AI) { | ||
| // not have any meaning for a local alloca. | ||
| if (SI->isVolatile()) | ||
| return false; | ||
| + } else if (const MemCpyInst *MCI = dyn_cast<MemCpyInst>(U)) { | ||
| + if (!isSplittableMemCpy(MCI, AI)) | ||
| + return false; | ||
| } else if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(U)) { | ||
| if (II->getIntrinsicID() != Intrinsic::lifetime_start && | ||
| II->getIntrinsicID() != Intrinsic::lifetime_end) | ||
| @@ -75,7 +130,7 @@ bool llvm::isAllocaPromotable(const AllocaInst *AI) { | ||
| } else if (const BitCastInst *BCI = dyn_cast<BitCastInst>(U)) { | ||
| if (BCI->getType() != Type::getInt8PtrTy(U->getContext(), AS)) | ||
| return false; | ||
| - if (!onlyUsedByLifetimeMarkers(BCI)) | ||
| + if (!onlyHasCanonicalizableUsers(AI, BCI)) | ||
| return false; | ||
| } else if (const GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) { | ||
| if (GEPI->getType() != Type::getInt8PtrTy(U->getContext(), AS)) | ||
| @@ -181,7 +235,13 @@ public: | ||
| /// This code only looks at accesses to allocas. | ||
| static bool isInterestingInstruction(const Instruction *I) { | ||
| + if (isa<MemCpyInst>(I)) { | ||
| + const MemCpyInst *MCI = cast<MemCpyInst>(I); | ||
| + return isa<AllocaInst>(MCI->getSource()) || | ||
| + isa<AllocaInst>(MCI->getDest()); | ||
| + } else { | ||
| return (isa<LoadInst>(I) && isa<AllocaInst>(I->getOperand(0))) || | ||
| (isa<StoreInst>(I) && isa<AllocaInst>(I->getOperand(1))); | ||
| } | ||
| + } | ||
|
|
||
| /// Get or calculate the index of the specified instruction. | ||
| @@ -208,6 +264,25 @@ public: | ||
| return It->second; | ||
| } | ||
|
|
||
| + // When we split a memcpy intrinsic, we need to update the numbering in this | ||
| + // struct. To make sure the relative ordering remains the same, we give both | ||
| + // the LI and the SI the number that the MCI used to have (if they are both | ||
| + // interesting). This means that they will have equal numbers, which usually | ||
| + // can't happen. However, since they can never reference the same alloca | ||
| + // (since memcpy operands may not overlap), this is fine, because we will | ||
| + // never compare instruction indices for instructions that operate on distinct | ||
| + // allocas. | ||
| + void splitMemCpy(MemCpyInst *MCI, LoadInst *LI, StoreInst *SI) { | ||
| + DenseMap<const Instruction *, unsigned>::iterator It = | ||
| + InstNumbers.find(MCI); | ||
| + if (It == InstNumbers.end()) | ||
| + return; | ||
| + unsigned MemCpyNumber = It->second; | ||
| + InstNumbers[LI] = MemCpyNumber; | ||
| + InstNumbers[SI] = MemCpyNumber; | ||
| + deleteValue(MCI); | ||
| + } | ||
| + | ||
| void deleteValue(const Instruction *I) { InstNumbers.erase(I); } | ||
|
|
||
| void clear() { InstNumbers.clear(); } | ||
| @@ -305,9 +380,58 @@ static void addAssumeNonNull(AssumptionCache *AC, LoadInst *LI) { | ||
| AC->registerAssumption(CI); | ||
| } | ||
|
|
||
| -static void removeLifetimeIntrinsicUsers(AllocaInst *AI) { | ||
| - // Knowing that this alloca is promotable, we know that it's safe to kill all | ||
| - // instructions except for load and store. | ||
| +/// Split a memcpy instruction into the corresponding load/store. It is a little | ||
| +/// more complicated than one might imagine, because we need to deal with the | ||
| +/// fact that the side of the copy we're not currently processing might also | ||
| +/// be a promotable alloca. We need to be careful to not break the promotable | ||
| +/// predicate for that other alloca (if any). | ||
| +static void doMemCpySplit(LargeBlockInfo &LBI, MemCpyInst *MCI, | ||
| + AllocaInst *AI) { | ||
| + AAMDNodes AA; | ||
| + MCI->getAAMetadata(AA); | ||
| + Value *MCISrc = MCI->getSource(); | ||
| + Type *LoadType = AI->getAllocatedType(); | ||
| + AllocaInst *SrcAI = dyn_cast<AllocaInst>(MCISrc); | ||
| + if (SrcAI && SrcAI->getType() != AI->getType()) { | ||
| + if (CastInst::isBitCastable(SrcAI->getAllocatedType(), LoadType)) | ||
| + LoadType = SrcAI->getAllocatedType(); | ||
| + } | ||
| + if (cast<PointerType>(MCISrc->getType())->getElementType() != LoadType) | ||
| + MCISrc = CastInst::Create( | ||
| + Instruction::BitCast, MCISrc, | ||
| + LoadType->getPointerTo( | ||
| + cast<PointerType>(MCISrc->getType())->getAddressSpace()), | ||
| + "", MCI); | ||
| + // This might add to the end of the use list, but that's fine. At worst, | ||
| + // we'd not visit the instructions we insert here, but we don't care | ||
| + // about them in this loop anyway. | ||
| + LoadInst *LI = new LoadInst(LoadType, MCISrc, "", MCI->isVolatile(), | ||
| + MCI->getAlignment(), MCI); | ||
| + Value *Val = LI; | ||
| + Value *MCIDest = MCI->getDest(); | ||
| + AllocaInst *DestAI = dyn_cast<AllocaInst>(MCIDest); | ||
| + Type *DestElTy = DestAI ? DestAI->getAllocatedType() : AI->getAllocatedType(); | ||
| + if (LI->getType() != DestElTy && | ||
| + CastInst::isBitCastable(LI->getType(), DestElTy)) | ||
| + Val = CastInst::Create(Instruction::BitCast, Val, DestElTy, "", MCI); | ||
| + if (cast<PointerType>(MCIDest->getType())->getElementType() != Val->getType()) | ||
| + MCIDest = CastInst::Create( | ||
| + Instruction::BitCast, MCIDest, | ||
| + Val->getType()->getPointerTo( | ||
| + cast<PointerType>(MCIDest->getType())->getAddressSpace()), | ||
| + "", MCI); | ||
| + StoreInst *SI = | ||
| + new StoreInst(Val, MCIDest, MCI->isVolatile(), MCI->getAlignment(), MCI); | ||
| + LI->setAAMetadata(AA); | ||
| + SI->setAAMetadata(AA); | ||
| + LBI.splitMemCpy(MCI, LI, SI); | ||
| + MCI->eraseFromParent(); | ||
| +} | ||
| + | ||
| +static void canonicalizeUsers(LargeBlockInfo &LBI, AllocaInst *AI) { | ||
| + // Knowing that this alloca is promotable, we know that it's safe to split | ||
| + // MTIs into load/store and to kill all other instructions except for | ||
| + // load and store. | ||
|
|
||
| for (auto UI = AI->user_begin(), UE = AI->user_end(); UI != UE;) { | ||
| Instruction *I = cast<Instruction>(*UI); | ||
| @@ -315,14 +439,24 @@ static void removeLifetimeIntrinsicUsers(AllocaInst *AI) { | ||
| if (isa<LoadInst>(I) || isa<StoreInst>(I)) | ||
| continue; | ||
|
|
||
| + if (isa<MemCpyInst>(I)) { | ||
| + MemCpyInst *MCI = cast<MemCpyInst>(I); | ||
| + doMemCpySplit(LBI, MCI, AI); | ||
| + continue; | ||
| + } | ||
| + | ||
| if (!I->getType()->isVoidTy()) { | ||
| - // The only users of this bitcast/GEP instruction are lifetime intrinsics. | ||
| - // Follow the use/def chain to erase them now instead of leaving it for | ||
| - // dead code elimination later. | ||
| + // The only users of this bitcast/GEP instruction are lifetime/memcpy | ||
| + // intrinsics. Split memcpys and delete lifetime intrinsics. | ||
| for (auto UUI = I->user_begin(), UUE = I->user_end(); UUI != UUE;) { | ||
| Instruction *Inst = cast<Instruction>(*UUI); | ||
| ++UUI; | ||
| - Inst->eraseFromParent(); | ||
| + if (isa<MemCpyInst>(Inst)) { | ||
| + doMemCpySplit(LBI, cast<MemCpyInst>(Inst), AI); | ||
| + } else { | ||
| + // Must be a lifetime intrinsic | ||
| + Inst->eraseFromParent(); | ||
| + } | ||
| } | ||
| } | ||
| I->eraseFromParent(); | ||
| @@ -542,7 +676,7 @@ void PromoteMem2Reg::run() { | ||
| assert(AI->getParent()->getParent() == &F && | ||
| "All allocas should be in the same function, which is same as DF!"); | ||
|
|
||
| - removeLifetimeIntrinsicUsers(AI); | ||
| + canonicalizeUsers(LBI, AI); | ||
|
|
||
| if (AI->use_empty()) { | ||
| // If there are no uses of the alloca, just delete it now. | ||
| diff --git a/test/Transforms/Mem2Reg/memcpy.ll b/test/Transforms/Mem2Reg/memcpy.ll | ||
| new file mode 100644 | ||
| index 0000000..fbc4096 | ||
| --- /dev/null | ||
| +++ b/test/Transforms/Mem2Reg/memcpy.ll | ||
| @@ -0,0 +1,101 @@ | ||
| +; RUN: opt < %s -mem2reg -S | FileCheck %s | ||
| + | ||
| +target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128" | ||
| + | ||
| +declare void @llvm.memcpy.p0i128.p0i64.i32(i128 *, i64 *, i32, i32, i1) | ||
| +declare void @llvm.memcpy.p0i8.p0i8.i32(i8 *, i8 *, i32, i32, i1) | ||
| +declare void @llvm.memcpy.p0i64.p0i64.i32(i64 *, i64 *, i32, i32, i1) | ||
| +declare void @llvm.memcpy.p0f64.p0i64.i32(double *, i64 *, i32, i32, i1) | ||
| + | ||
| +define i128 @test_cpy_different(i64) { | ||
| +; CHECK-LABEL: @test_cpy_different | ||
| +; CHECK-NOT: alloca i64 | ||
| +; CHECK: store i64 %0 | ||
| + %a = alloca i64 | ||
| + %b = alloca i128 | ||
| + store i128 0, i128 *%b | ||
| + store i64 %0, i64 *%a | ||
| + call void @llvm.memcpy.p0i128.p0i64.i32(i128 *%b, i64 *%a, i32 8, i32 0, i1 0) | ||
| + %loaded = load i128, i128 *%b | ||
| + ret i128 %loaded | ||
| +} | ||
| + | ||
| +define i64 @test_cpy_same(i64) { | ||
| +; CHECK-LABEL: @test_cpy_same | ||
| +; CHECK-NOT: alloca | ||
| +; CHECK: ret i64 %0 | ||
| + %a = alloca i64 | ||
| + %b = alloca i64 | ||
| + store i64 %0, i64 *%a | ||
| + call void @llvm.memcpy.p0i64.p0i64.i32(i64 *%b, i64 *%a, i32 8, i32 0, i1 0) | ||
| + %loaded = load i64, i64 *%b | ||
| + ret i64 %loaded | ||
| +} | ||
| + | ||
| +define double @test_cpy_different_type(i64) { | ||
| +; CHECK-LABEL: @test_cpy_different_type | ||
| +; CHECK-NOT: alloca | ||
| +; CHECK: bitcast i64 %0 to double | ||
| + %a = alloca i64 | ||
| + %b = alloca double | ||
| + store i64 %0, i64 *%a | ||
| + call void @llvm.memcpy.p0f64.p0i64.i32(double *%b, i64 *%a, i32 8, i32 0, i1 0) | ||
| + %loaded = load double, double *%b | ||
| + ret double %loaded | ||
| +} | ||
| + | ||
| +define i128 @test_cpy_differenti8(i64) { | ||
| +; CHECK-LABEL: @test_cpy_differenti8 | ||
| +; CHECK-NOT: alloca i64 | ||
| +; CHECK: store i64 %0 | ||
| + %a = alloca i64 | ||
| + %b = alloca i128 | ||
| + store i128 0, i128 *%b | ||
| + store i64 %0, i64 *%a | ||
| + %acast = bitcast i64* %a to i8* | ||
| + %bcast = bitcast i128* %b to i8* | ||
| + call void @llvm.memcpy.p0i8.p0i8.i32(i8 *%bcast, i8 *%acast, i32 8, i32 0, i1 0) | ||
| + %loaded = load i128, i128 *%b | ||
| + ret i128 %loaded | ||
| +} | ||
| + | ||
| +define i64 @test_cpy_samei8(i64) { | ||
| +; CHECK-LABEL: @test_cpy_samei8 | ||
| +; CHECK-NOT: alloca | ||
| +; CHECK: ret i64 %0 | ||
| + %a = alloca i64 | ||
| + %b = alloca i64 | ||
| + store i64 %0, i64 *%a | ||
| + %acast = bitcast i64* %a to i8* | ||
| + %bcast = bitcast i64* %b to i8* | ||
| + call void @llvm.memcpy.p0i8.p0i8.i32(i8 *%bcast, i8 *%acast, i32 8, i32 0, i1 0) | ||
| + %loaded = load i64, i64 *%b | ||
| + ret i64 %loaded | ||
| +} | ||
| + | ||
| +define double @test_cpy_different_typei8(i64) { | ||
| +; CHECK-LABEL: @test_cpy_different_typei8 | ||
| +; CHECK-NOT: alloca | ||
| +; CHECK: bitcast i64 %0 to double | ||
| + %a = alloca i64 | ||
| + %b = alloca double | ||
| + store i64 %0, i64 *%a | ||
| + %acast = bitcast i64* %a to i8* | ||
| + %bcast = bitcast double* %b to i8* | ||
| + call void @llvm.memcpy.p0i8.p0i8.i32(i8 *%bcast, i8 *%acast, i32 8, i32 0, i1 0) | ||
| + %loaded = load double, double *%b | ||
| + ret double %loaded | ||
| +} | ||
| + | ||
| +define i64 @test_cpy_differenti8_reverse(i128) { | ||
| +; CHECK-LABEL: @test_cpy_differenti8_reverse | ||
| +; CHECK-NOT: alloca i64 | ||
| + %a = alloca i64 | ||
| + %b = alloca i128 | ||
| + store i128 %0, i128 *%b | ||
| + %acast = bitcast i64* %a to i8* | ||
| + %bcast = bitcast i128* %b to i8* | ||
| + call void @llvm.memcpy.p0i8.p0i8.i32(i8 *%acast, i8 *%bcast, i32 8, i32 0, i1 0) | ||
| + %loaded = load i64, i64 *%a | ||
| + ret i64 %loaded | ||
| +} | ||
| -- | ||
| 2.9.3 | ||
|
|
||
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rudimentary