[CodeGenPrepare] Mend "avoid crashing from replacing a phi twice" fix.

Summary:
An erroneously negated if-statement by an earlier (March 2019) bugfix left phi replacement/simplification under optimizeMemoryInst()  in CodeGenPrepare largely inactivated. The error was found when csmith found that the same assert as in the original bug report could still be triggered in a different way. This patch fixes the bugfix. The original bug was:
 https://bugs.llvm.org/show_bug.cgi?id=41052
... and the previous fix was D59358.

Reviewers: aprantl, skatkov

Reviewed By: skatkov

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D67838

llvm-svn: 373084

1 files changed, 1 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/CodeGenPrepare.cpp b/llvm/lib/CodeGen/CodeGenPrepare.cpp
index b3a6e284f4f..c74428051b2 100644
--- a/llvm/lib/CodeGen/CodeGenPrepare.cpp
+++ b/llvm/lib/CodeGen/CodeGenPrepare.cpp
@@ -3332,7 +3332,7 @@ private:
         // So the values are different and does not match. So we need them to
         // match. (But we register no more than one match per PHI node, so that
         // we won't later try to replace them twice.)
-        if (!MatchedPHIs.insert(FirstPhi).second)
+        if (MatchedPHIs.insert(FirstPhi).second)
           Matcher.insert({ FirstPhi, SecondPhi });
         // But me must check it.
         WorkList.push_back({ FirstPhi, SecondPhi });