From 7aeae25c78197800a931d56a10cad062a7711a46 Mon Sep 17 00:00:00 2001 From: Chris Lattner Date: Thu, 18 Nov 2010 06:20:47 +0000 Subject: fix a small oversight in the "eliminate memcpy from constant global" optimization. If the alloca that is "memcpy'd from constant" also has a memcpy from *it*, ignore it: it is a load. We now optimize the testcase to: define void @test2() { %B = alloca %T %a = bitcast %T* @G to i8* %b = bitcast %T* %B to i8* call void @llvm.memcpy.p0i8.p0i8.i64(i8* %b, i8* %a, i64 124, i32 4, i1 false) call void @bar(i8* %b) ret void } previously we would generate: define void @test() { %B = alloca %T %b = bitcast %T* %B to i8* %G.0 = getelementptr inbounds %T* @G, i32 0, i32 0 %tmp3 = load i8* %G.0, align 4 %G.1 = getelementptr inbounds %T* @G, i32 0, i32 1 %G.15 = bitcast [123 x i8]* %G.1 to i8* %1 = bitcast [123 x i8]* %G.1 to i984* %srcval = load i984* %1, align 1 %B.0 = getelementptr inbounds %T* %B, i32 0, i32 0 store i8 %tmp3, i8* %B.0, align 4 %B.1 = getelementptr inbounds %T* %B, i32 0, i32 1 %B.12 = bitcast [123 x i8]* %B.1 to i8* %2 = bitcast [123 x i8]* %B.1 to i984* store i984 %srcval, i984* %2, align 1 call void @bar(i8* %b) ret void } llvm-svn: 119682 --- llvm/lib/Transforms/Scalar/ScalarReplAggregates.cpp | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) (limited to 'llvm/lib/Transforms') diff --git a/llvm/lib/Transforms/Scalar/ScalarReplAggregates.cpp b/llvm/lib/Transforms/Scalar/ScalarReplAggregates.cpp index 8b4f35570d0..6f4f17e20fb 100644 --- a/llvm/lib/Transforms/Scalar/ScalarReplAggregates.cpp +++ b/llvm/lib/Transforms/Scalar/ScalarReplAggregates.cpp @@ -1789,10 +1789,11 @@ static bool isOnlyCopiedFromConstantGlobal(Value *V, MemTransferInst *&TheCopy, for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) { User *U = cast(*UI); - if (LoadInst *LI = dyn_cast(U)) + if (LoadInst *LI = dyn_cast(U)) { // Ignore non-volatile loads, they are always ok. - if (!LI->isVolatile()) - continue; + if (LI->isVolatile()) return false; + continue; + } if (BitCastInst *BCI = dyn_cast(U)) { // If uses of the bitcast are ok, we are ok. @@ -1814,6 +1815,13 @@ static bool isOnlyCopiedFromConstantGlobal(Value *V, MemTransferInst *&TheCopy, MemTransferInst *MI = dyn_cast(U); if (MI == 0) return false; + + // If the transfer is using the alloca as a source of the transfer, then + // it (unless the transfer is volatile). + if (UI.getOperandNo() == 1) { + if (MI->isVolatile()) return false; + continue; + } // If we already have seen a copy, reject the second one. if (TheCopy) return false; -- cgit v1.2.3