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author | Chandler Carruth <chandlerc@gmail.com> | 2014-02-25 21:54:50 +0000 |
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committer | Chandler Carruth <chandlerc@gmail.com> | 2014-02-25 21:54:50 +0000 |
commit | 9c256eccb355fb26072ad5353a2f886f62118aa8 (patch) | |
tree | f5ef399f578d4808c781c47ad77b83654a06dd7b /lib | |
parent | 431e9f03106ad217af461780836cd7f4bb075a5d (diff) | |
download | llvm-9c256eccb355fb26072ad5353a2f886f62118aa8.tar.gz llvm-9c256eccb355fb26072ad5353a2f886f62118aa8.tar.bz2 llvm-9c256eccb355fb26072ad5353a2f886f62118aa8.tar.xz |
[reassociate] Switch two std::sort calls into std::stable_sort calls as
their inputs come from std::stable_sort and they are not total orders.
I'm not a huge fan of this, but the really bad std::stable_sort is right
at the beginning of Reassociate. After we commit to stable-sort based
consistent respect of source order, the downstream sorts shouldn't undo
that unless they have a total order or they are used in an
order-insensitive way. Neither appears to be true for these cases.
I don't have particularly good test cases, but this jumped out by
inspection when looking for output instability in this pass due to
changes in the ordering of std::sort.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202196 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib')
-rw-r--r-- | lib/Transforms/Scalar/Reassociate.cpp | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/lib/Transforms/Scalar/Reassociate.cpp b/lib/Transforms/Scalar/Reassociate.cpp index 1a387f60e1..e6d7abe3eb 100644 --- a/lib/Transforms/Scalar/Reassociate.cpp +++ b/lib/Transforms/Scalar/Reassociate.cpp @@ -1292,7 +1292,7 @@ Value *Reassociate::OptimizeXor(Instruction *I, // the same symbolic value cluster together. For instance, the input operand // sequence ("x | 123", "y & 456", "x & 789") will be sorted into: // ("x | 123", "x & 789", "y & 456"). - std::sort(OpndPtrs.begin(), OpndPtrs.end(), XorOpnd::PtrSortFunctor()); + std::stable_sort(OpndPtrs.begin(), OpndPtrs.end(), XorOpnd::PtrSortFunctor()); // Step 3: Combine adjacent operands XorOpnd *PrevOpnd = 0; @@ -1618,7 +1618,7 @@ bool Reassociate::collectMultiplyFactors(SmallVectorImpl<ValueEntry> &Ops, // below our mininum of '4'. assert(FactorPowerSum >= 4); - std::sort(Factors.begin(), Factors.end(), Factor::PowerDescendingSorter()); + std::stable_sort(Factors.begin(), Factors.end(), Factor::PowerDescendingSorter()); return true; } |