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SLPVectorizer: Instead of just performing CSE on dead blocks ignore them completely.

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Turns out that there is a very cheap way of testing whether a block is dead,
just look it up in the DomTree. We have to do this anyways so just ignore
unreachable blocks before sorting by domination. This restores a proper
ordering for std::stable_sort when dead code is present.

Covered by existing tests & buildbots running in STL debug mode (MSVC).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@208492 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Benjamin Kramer 2014-05-11 10:28:58 +00:00
parent f5e04c38cd
commit 4db3f41012
1 changed files with 13 additions and 8 deletions
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21
lib/Transforms/Vectorize/SLPVectorizer.cpp
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@ -1812,11 +1812,19 @@ void BoUpSLP::optimizeGatherSequence() {
Insert->moveBefore(PreHeader->getTerminator()); Insert->moveBefore(PreHeader->getTerminator());
} }
// Make a list of all reachable blocks in our CSE queue.
SmallVector<const DomTreeNode *, 8> CSEWorkList;
CSEWorkList.reserve(CSEBlocks.size());
for (BasicBlock *BB : CSEBlocks)
if (DomTreeNode *N = DT->getNode(BB)) {
assert(DT->isReachableFromEntry(N));
CSEWorkList.push_back(N);
}
// Sort blocks by domination. This ensures we visit a block after all blocks // Sort blocks by domination. This ensures we visit a block after all blocks
// dominating it are visited. // dominating it are visited.
SmallVector<BasicBlock *, 8> CSEWorkList(CSEBlocks.begin(), CSEBlocks.end());
std::stable_sort(CSEWorkList.begin(), CSEWorkList.end(), std::stable_sort(CSEWorkList.begin(), CSEWorkList.end(),
[this](const BasicBlock *A, const BasicBlock *B) { [this](const DomTreeNode *A, const DomTreeNode *B) {
return DT->properlyDominates(A, B); return DT->properlyDominates(A, B);
}); });
@ -1824,13 +1832,10 @@ void BoUpSLP::optimizeGatherSequence() {
// instructions. TODO: We can further optimize this scan if we split the // instructions. TODO: We can further optimize this scan if we split the
// instructions into different buckets based on the insert lane. // instructions into different buckets based on the insert lane.
SmallVector<Instruction *, 16> Visited; SmallVector<Instruction *, 16> Visited;
for (SmallVectorImpl<BasicBlock *>::iterator I = CSEWorkList.begin(), for (auto I = CSEWorkList.begin(), E = CSEWorkList.end(); I != E; ++I) {
E = CSEWorkList.end(); assert((I == CSEWorkList.begin() || !DT->dominates(*I, *std::prev(I))) &&
I != E; ++I) {
assert((I == CSEWorkList.begin() || !DT->isReachableFromEntry(*I) ||
!DT->dominates(*I, *std::prev(I))) &&
"Worklist not sorted properly!"); "Worklist not sorted properly!");
BasicBlock *BB = *I; BasicBlock *BB = (*I)->getBlock();
// For all instructions in blocks containing gather sequences: // For all instructions in blocks containing gather sequences:
for (BasicBlock::iterator it = BB->begin(), e = BB->end(); it != e;) { for (BasicBlock::iterator it = BB->begin(), e = BB->end(); it != e;) {
Instruction *In = it++; Instruction *In = it++;