From d5fdef016d0d957d8712b07e9e5828b9dae5c944 Mon Sep 17 00:00:00 2001 From: Tim Northover Date: Tue, 14 Jul 2015 21:03:18 +0000 Subject: [PATCH] GVN: tolerate an instruction being replaced without existing in the leaderboard Sometimes an incidentally created instruction can duplicate a Value used elsewhere. It then often doesn't end up in the leader table. If it's later removed, we attempt to remove it from the leader table and segfault. Instead we should just ignore the removal request, which won't cause any problems. The reverse situation, where the original instruction is replaced by the new one (which you might think could leave the leader table empty) cannot occur, because the incidental instruction will never be found in the first place. llvm-svn: 242199 --- llvm/lib/Transforms/Scalar/GVN.cpp | 5 ++++- llvm/test/Transforms/GVN/pre-new-inst.ll | 29 +++++++++++++++++++++++++++++ 2 files changed, 33 insertions(+), 1 deletion(-) create mode 100644 llvm/test/Transforms/GVN/pre-new-inst.ll diff --git a/llvm/lib/Transforms/Scalar/GVN.cpp b/llvm/lib/Transforms/Scalar/GVN.cpp index 2c47a8a..b1a0db3 100644 --- a/llvm/lib/Transforms/Scalar/GVN.cpp +++ b/llvm/lib/Transforms/Scalar/GVN.cpp @@ -656,11 +656,14 @@ namespace { LeaderTableEntry* Prev = nullptr; LeaderTableEntry* Curr = &LeaderTable[N]; - while (Curr->Val != I || Curr->BB != BB) { + while (Curr && (Curr->Val != I || Curr->BB != BB)) { Prev = Curr; Curr = Curr->Next; } + if (!Curr) + return; + if (Prev) { Prev->Next = Curr->Next; } else { diff --git a/llvm/test/Transforms/GVN/pre-new-inst.ll b/llvm/test/Transforms/GVN/pre-new-inst.ll new file mode 100644 index 0000000..238b8a6 --- /dev/null +++ b/llvm/test/Transforms/GVN/pre-new-inst.ll @@ -0,0 +1,29 @@ +; RUN: opt -basicaa -gvn -S %s | FileCheck %s + +%MyStruct = type { i32, i32 } +define i8 @foo(i64 %in, i8* %arr) { + %addr = alloca %MyStruct + %dead = trunc i64 %in to i32 + br i1 undef, label %next, label %tmp + +tmp: + call void @bar() + br label %next + +next: + %addr64 = bitcast %MyStruct* %addr to i64* + store i64 %in, i64* %addr64 + br label %final + +final: + %addr32 = getelementptr %MyStruct, %MyStruct* %addr, i32 0, i32 0 + %idx32 = load i32, i32* %addr32 + +; CHECK: %resptr = getelementptr i8, i8* %arr, i32 %dead + %resptr = getelementptr i8, i8* %arr, i32 %idx32 + %res = load i8, i8* %resptr + + ret i8 %res +} + +declare void @bar() -- 2.7.4