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author | Stepan Dyatkovskiy <stpworld@narod.ru> | 2014-01-27 09:18:31 +0000 |
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committer | Stepan Dyatkovskiy <stpworld@narod.ru> | 2014-01-27 09:18:31 +0000 |
commit | c628af024e7f1716161241e1e3fb7037b6a078fa (patch) | |
tree | 306f345521efeca1ff304a89fd9d8c2290bcc1ae /lib/CodeGen | |
parent | 0afd0bc5facb63a96c706dc8a2468327ee3161da (diff) | |
download | llvm-c628af024e7f1716161241e1e3fb7037b6a078fa.tar.gz llvm-c628af024e7f1716161241e1e3fb7037b6a078fa.tar.bz2 llvm-c628af024e7f1716161241e1e3fb7037b6a078fa.tar.xz |
Fix for PR18102.
Issue outcomes from DAGCombiner::MergeConsequtiveStores, more precisely from
mem-ops sequence sorting.
Consider, how MergeConsequtiveStores works for next example:
store i8 1, a[0]
store i8 2, a[1]
store i8 3, a[1] ; a[1] again.
return ; DAG starts here
1. Method will collect all the 3 stores.
2. It sorts them by distance from the base pointer (farthest with highest
index).
3. It takes first consecutive non-overlapping stores and (if possible) replaces
them with a single store instruction.
The point is, we can't determine here which 'store' instruction
would be the second after sorting ('store 2' or 'store 3').
It happens that 'store 3' would be the second, and 'store 2' would be the third.
So after merging we have the next result:
store i16 (1 | 3 << 8), base ; is a[0] but bit-casted to i16
store i8 2, a[1]
So actually we swapped 'store 3' and 'store 2' and got wrong contents in a[1].
Fix: In sort routine just also take into account mem-op sequence number.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200201 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/CodeGen')
-rw-r--r-- | lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index b95a6c1198..97c19d0e9b 100644 --- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -8761,7 +8761,10 @@ struct MemOpLink { // base ptr. struct ConsecutiveMemoryChainSorter { bool operator()(MemOpLink LHS, MemOpLink RHS) { - return LHS.OffsetFromBase < RHS.OffsetFromBase; + return + LHS.OffsetFromBase < RHS.OffsetFromBase || + (LHS.OffsetFromBase == RHS.OffsetFromBase && + LHS.SequenceNum > RHS.SequenceNum); } }; |