From 0c826d98b39e941fad96ffaf32c23d3fae447a19 Mon Sep 17 00:00:00 2001 From: Eli Friedman Date: Thu, 17 Dec 2009 21:07:31 +0000 Subject: [PATCH] Slightly generalize transformation of memmove(a,a,n) so that it also applies to memcpy. (Such a memcpy is technically illegal, but in practice is safe and is generated by struct self-assignment in C code.) git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@91621 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/Scalar/InstructionCombining.cpp | 4 +++- test/Transforms/InstCombine/memcpy.ll | 10 ++++++++++ 2 files changed, 13 insertions(+), 1 deletion(-) create mode 100644 test/Transforms/InstCombine/memcpy.ll diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp index b9c536fe1e5..c7359c4de76 100644 --- a/lib/Transforms/Scalar/InstructionCombining.cpp +++ b/lib/Transforms/Scalar/InstructionCombining.cpp @@ -9896,9 +9896,11 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) { Intrinsic::getDeclaration(M, MemCpyID, Tys, 1)); Changed = true; } + } + if (MemTransferInst *MTI = dyn_cast(MI)) { // memmove(x,x,size) -> noop. - if (MMI->getSource() == MMI->getDest()) + if (MTI->getSource() == MTI->getDest()) return EraseInstFromFunction(CI); } diff --git a/test/Transforms/InstCombine/memcpy.ll b/test/Transforms/InstCombine/memcpy.ll new file mode 100644 index 00000000000..2e7b2c0bb41 --- /dev/null +++ b/test/Transforms/InstCombine/memcpy.ll @@ -0,0 +1,10 @@ +; RUN: opt < %s -instcombine -S | FileCheck %s + +declare void @llvm.memcpy.i32(i8*, i8*, i32, i32) + +define void @test4(i8* %a) { + tail call void @llvm.memcpy.i32( i8* %a, i8* %a, i32 100, i32 1 ) + ret void +} +; CHECK: define void @test4 +; CHECK-NEXT: ret void -- 2.34.1