From c2c0bd357f8c3a619545fed03aa090bf064e9ccd Mon Sep 17 00:00:00 2001 From: Hans Wennborg Date: Fri, 31 Aug 2018 15:53:05 +0000 Subject: [PATCH] Merging r341094: ------------------------------------------------------------------------ r341094 | efriedma | 2018-08-30 20:59:24 +0200 (Thu, 30 Aug 2018) | 11 lines [SROA] Fix alignment for uses of PHI nodes. Splitting an alloca can decrease the alignment of GEPs into the partition. Normally, rewriting accounts for this, but the code was missing for uses of PHI nodes and select instructions. Fixes https://bugs.llvm.org/show_bug.cgi?id=38707 . Differential Revision: https://reviews.llvm.org/D51335 ------------------------------------------------------------------------ git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_70@341220 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/Scalar/SROA.cpp | 42 ++++++++++++++++++++++++++ test/Transforms/SROA/phi-and-select.ll | 32 ++++++++++++++++++++ 2 files changed, 74 insertions(+) diff --git a/lib/Transforms/Scalar/SROA.cpp b/lib/Transforms/Scalar/SROA.cpp index de16b608f752..bf482bf5272e 100644 --- a/lib/Transforms/Scalar/SROA.cpp +++ b/lib/Transforms/Scalar/SROA.cpp @@ -3046,6 +3046,42 @@ class llvm::sroa::AllocaSliceRewriter return true; } + void fixLoadStoreAlign(Instruction &Root) { + // This algorithm implements the same visitor loop as + // hasUnsafePHIOrSelectUse, and fixes the alignment of each load + // or store found. + SmallPtrSet Visited; + SmallVector Uses; + Visited.insert(&Root); + Uses.push_back(&Root); + do { + Instruction *I = Uses.pop_back_val(); + + if (LoadInst *LI = dyn_cast(I)) { + unsigned LoadAlign = LI->getAlignment(); + if (!LoadAlign) + LoadAlign = DL.getABITypeAlignment(LI->getType()); + LI->setAlignment(std::min(LoadAlign, getSliceAlign())); + continue; + } + if (StoreInst *SI = dyn_cast(I)) { + unsigned StoreAlign = SI->getAlignment(); + if (!StoreAlign) { + Value *Op = SI->getOperand(0); + StoreAlign = DL.getABITypeAlignment(Op->getType()); + } + SI->setAlignment(std::min(StoreAlign, getSliceAlign())); + continue; + } + + assert(isa(I) || isa(I) || + isa(I) || isa(I)); + for (User *U : I->users()) + if (Visited.insert(cast(U)).second) + Uses.push_back(cast(U)); + } while (!Uses.empty()); + } + bool visitPHINode(PHINode &PN) { LLVM_DEBUG(dbgs() << " original: " << PN << "\n"); assert(BeginOffset >= NewAllocaBeginOffset && "PHIs are unsplittable"); @@ -3069,6 +3105,9 @@ class llvm::sroa::AllocaSliceRewriter LLVM_DEBUG(dbgs() << " to: " << PN << "\n"); deleteIfTriviallyDead(OldPtr); + // Fix the alignment of any loads or stores using this PHI node. + fixLoadStoreAlign(PN); + // PHIs can't be promoted on their own, but often can be speculated. We // check the speculation outside of the rewriter so that we see the // fully-rewritten alloca. @@ -3093,6 +3132,9 @@ class llvm::sroa::AllocaSliceRewriter LLVM_DEBUG(dbgs() << " to: " << SI << "\n"); deleteIfTriviallyDead(OldPtr); + // Fix the alignment of any loads or stores using this select. + fixLoadStoreAlign(SI); + // Selects can't be promoted on their own, but often can be speculated. We // check the speculation outside of the rewriter so that we see the // fully-rewritten alloca. diff --git a/test/Transforms/SROA/phi-and-select.ll b/test/Transforms/SROA/phi-and-select.ll index fb76548b1d18..e7ba2e89d795 100644 --- a/test/Transforms/SROA/phi-and-select.ll +++ b/test/Transforms/SROA/phi-and-select.ll @@ -600,3 +600,35 @@ if.then5: ; preds = %if.then2, %if.end store %struct.S undef, %struct.S* %f1, align 4 ret void } + +define i32 @phi_align(i32* %z) { +; CHECK-LABEL: @phi_align( +entry: + %a = alloca [8 x i8], align 8 +; CHECK: alloca [7 x i8] + + %a0x = getelementptr [8 x i8], [8 x i8]* %a, i64 0, i32 1 + %a0 = bitcast i8* %a0x to i32* + %a1x = getelementptr [8 x i8], [8 x i8]* %a, i64 0, i32 4 + %a1 = bitcast i8* %a1x to i32* +; CHECK: store i32 0, {{.*}}, align 1 + store i32 0, i32* %a0, align 1 +; CHECK: store i32 1, {{.*}}, align 1 + store i32 1, i32* %a1, align 4 +; CHECK: load {{.*}}, align 1 + %v0 = load i32, i32* %a0, align 1 +; CHECK: load {{.*}}, align 1 + %v1 = load i32, i32* %a1, align 4 + %cond = icmp sle i32 %v0, %v1 + br i1 %cond, label %then, label %exit + +then: + br label %exit + +exit: +; CHECK: %phi = phi i32* [ {{.*}}, %then ], [ %z, %entry ] +; CHECK-NEXT: %result = load i32, i32* %phi, align 1 + %phi = phi i32* [ %a1, %then ], [ %z, %entry ] + %result = load i32, i32* %phi, align 4 + ret i32 %result +}