From 3bd19d753baf13577a43e0375bd7283379ad914a Mon Sep 17 00:00:00 2001 From: Bob Wilson Date: Tue, 2 Mar 2010 00:09:29 +0000 Subject: [PATCH] Don't attempt load PRE when there is no real redundancy (i.e., the load is in a loop and is itself the only dependency). git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@97526 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/Scalar/GVN.cpp | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/lib/Transforms/Scalar/GVN.cpp b/lib/Transforms/Scalar/GVN.cpp index a4c07160249..fcb802a72ae 100644 --- a/lib/Transforms/Scalar/GVN.cpp +++ b/lib/Transforms/Scalar/GVN.cpp @@ -1542,11 +1542,13 @@ bool GVN::processNonLocalLoad(LoadInst *LI, // at least one of the values is LI. Since this means that we won't be able // to eliminate LI even if we insert uses in the other predecessors, we will // end up increasing code size. Reject this by scanning for LI. - if (!EnableFullLoadPRE) { - for (unsigned i = 0, e = ValuesPerBlock.size(); i != e; ++i) - if (ValuesPerBlock[i].isSimpleValue() && - ValuesPerBlock[i].getSimpleValue() == LI) + for (unsigned i = 0, e = ValuesPerBlock.size(); i != e; ++i) { + if (ValuesPerBlock[i].isSimpleValue() && + ValuesPerBlock[i].getSimpleValue() == LI) { + // Skip cases where LI is the only definition, even for EnableFullLoadPRE. + if (!EnableFullLoadPRE || e == 1) return false; + } } // FIXME: It is extremely unclear what this loop is doing, other than