From f79f136cc64b0625b77c7b9008ed8c5b848b6b17 Mon Sep 17 00:00:00 2001
From: Hal Finkel <hfinkel@anl.gov>
Date: Sun, 17 Feb 2013 15:59:26 +0000
Subject: BBVectorize: Fix an invalid reference bug

This fixes PR15289. This bug was introduced (recently) in r175215; collecting
all std::vector references for candidate pairs to delete at once is invalid
because subsequent lookups in the owning DenseMap could invalidate the
references.

bugpoint was able to reduce a useful test case. Unfortunately, because whether
or not this asserts depends on memory layout, this test case will sometimes
appear to produce valid output. Nevertheless, running under valgrind will
reveal the error.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175397 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Vectorize/BBVectorize.cpp | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

(limited to 'lib/Transforms/Vectorize/BBVectorize.cpp')

diff --git a/lib/Transforms/Vectorize/BBVectorize.cpp b/lib/Transforms/Vectorize/BBVectorize.cpp
index 1773cff3bb..76365417aa 100644
--- a/lib/Transforms/Vectorize/BBVectorize.cpp
+++ b/lib/Transforms/Vectorize/BBVectorize.cpp
@@ -2164,10 +2164,7 @@ namespace {
                *S->second << "\n");
 
         // Remove all candidate pairs that have values in the chosen dag.
-        std::vector<Value *> &KK = CandidatePairs[S->first],
-                             &LL = CandidatePairs2[S->second],
-                             &MM = CandidatePairs[S->second],
-                             &NN = CandidatePairs2[S->first];
+        std::vector<Value *> &KK = CandidatePairs[S->first];
         for (std::vector<Value *>::iterator K = KK.begin(), KE = KK.end();
              K != KE; ++K) {
           if (*K == S->second)
@@ -2175,6 +2172,8 @@ namespace {
 
           CandidatePairsSet.erase(ValuePair(S->first, *K));
         }
+
+        std::vector<Value *> &LL = CandidatePairs2[S->second];
         for (std::vector<Value *>::iterator L = LL.begin(), LE = LL.end();
              L != LE; ++L) {
           if (*L == S->first)
@@ -2182,11 +2181,15 @@ namespace {
 
           CandidatePairsSet.erase(ValuePair(*L, S->second));
         }
+
+        std::vector<Value *> &MM = CandidatePairs[S->second];
         for (std::vector<Value *>::iterator M = MM.begin(), ME = MM.end();
              M != ME; ++M) {
           assert(*M != S->first && "Flipped pair in candidate list?");
           CandidatePairsSet.erase(ValuePair(S->second, *M));
         }
+
+        std::vector<Value *> &NN = CandidatePairs2[S->first];
         for (std::vector<Value *>::iterator N = NN.begin(), NE = NN.end();
              N != NE; ++N) {
           assert(*N != S->second && "Flipped pair in candidate list?");
-- 
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