From 5b7b529be0c28d8a9ae5ca89c6770f2516bac9c6 Mon Sep 17 00:00:00 2001 From: Mehdi Amini Date: Wed, 18 Nov 2015 22:49:49 +0000 Subject: [PATCH] Fix returned value for GVN: could return "false" even after modifying the IR This bug would manifest in some very specific cases where all the following conditions are fullfilled: - GVN didn't remove block - The regular GVN iteration didn't change the IR - PRE is enabled - PRE will not split critical edge - The last instruction processed by PRE didn't change the IR Because the CallGraph PassManager relies on this returned value to decide if it needs to recompute a node after the execution of Function passes, not returning the right value can lead to unexpected results. Fix for: https://llvm.org/bugs/show_bug.cgi?id=24715 Patch by Wenxiang Qiu From: Mehdi Amini git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@253518 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/Scalar/GVN.cpp | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/lib/Transforms/Scalar/GVN.cpp b/lib/Transforms/Scalar/GVN.cpp index d261b2acae9..1cb7198e9ee 100644 --- a/lib/Transforms/Scalar/GVN.cpp +++ b/lib/Transforms/Scalar/GVN.cpp @@ -2709,7 +2709,7 @@ bool GVN::performPRE(Function &F) { BE = CurrentBlock->end(); BI != BE;) { Instruction *CurInst = &*BI++; - Changed = performScalarPRE(CurInst); + Changed |= performScalarPRE(CurInst); } } -- 2.34.1