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BBVectorize: Don't vectorize vector-manipulation chains

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Don't choose a vectorization plan containing only shuffles and
vector inserts/extracts. Due to inperfections in the cost model,
these can lead to infinite recusion.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167811 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Hal Finkel
2012-11-13 03:12:40 +00:00
parent 310fa65ab9
commit 4387b8c959
2 changed files with 187 additions and 0 deletions
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17
lib/Transforms/Vectorize/BBVectorize.cpp
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@ -1703,10 +1703,20 @@ assert(n < 10 && "hrmm, really?");
// The set of pairs that have already contributed to the total cost.
DenseSet<ValuePair> IncomingPairs;
// If the cost model were perfect, this might not be necessary; but we
// need to make sure that we don't get stuck vectorizing our own
// shuffle chains.
bool HasNontrivialInsts = false;
// The node weights represent the cost savings associated with
// fusing the pair of instructions.
for (DenseSet<ValuePair>::iterator S = PrunedTree.begin(),
E = PrunedTree.end(); S != E; ++S) {
if (!isa<ShuffleVectorInst>(S->first) &&
!isa<InsertElementInst>(S->first) &&
!isa<ExtractElementInst>(S->first))
HasNontrivialInsts = true;
bool FlipOrder = false;
if (getDepthFactor(S->first)) {
@ -1943,6 +1953,13 @@ assert(n < 10 && "hrmm, really?");
}
}
}
if (!HasNontrivialInsts) {
DEBUG(if (DebugPairSelection) dbgs() <<
"\tNo non-trivial instructions in tree;"
" override to zero effective size\n");
EffSize = 0;
}
} else {
for (DenseSet<ValuePair>::iterator S = PrunedTree.begin(),
E = PrunedTree.end(); S != E; ++S)