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HotColdSplit: fix isSingleEntrySingleExit

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remove duplicate entries from isSingleEntrySingleExit: the Entry block is
already added by the loop over the dominance frontier.

Remove the heuristic from isOutlineCandidate that a region is too small when it
only contains a basic block. With this change we now grow regions starting from
a block and we continue adding to the ValidColdRegion. Check the heuristic just
before code generation.

llvm-svn: 342276
This commit is contained in:
Sebastian Pop 2018-09-14 20:36:14 +00:00
parent edc846cb9a
commit 02b10d9b76
1 changed files with 6 additions and 10 deletions
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16
lib/Transforms/IPO/HotColdSplitting.cpp
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@ -87,7 +87,6 @@ static bool isSingleEntrySingleExit(BasicBlock *Entry, const BasicBlock *Exit,
if (!PDT->dominates(Exit, Entry))
return false;
Region.push_back(Entry);
for (auto I = df_begin(Entry), E = df_end(Entry); I != E;) {
if (*I == Exit) {
I.skipChildren();
@ -230,9 +229,7 @@ private:
const BasicBlock *Exit) const {
if (!Exit)
return false;
// TODO: Find a better metric to compute the size of region being outlined.
if (Region.size() == 1)
return false;
// Regions with landing pads etc.
for (const BasicBlock *BB : Region) {
if (BB->isEHPad() || BB->hasAddressTaken())
@ -344,8 +341,7 @@ Function *HotColdSplitting::outlineColdBlocks(Function &F,
BasicBlock *BB = *I;
if (PSI->isColdBB(BB, BFI) || !HotBlocks.count(BB)) {
SmallVector<BasicBlock *, 4> ValidColdRegion, Region;
auto *BBNode = (*PDT)[BB];
auto Exit = BBNode->getIDom()->getBlock();
BasicBlock *Exit = (*PDT)[BB]->getIDom()->getBlock();
// We might need a virtual exit which post-dominates all basic blocks.
if (!Exit)
continue;
@ -360,12 +356,12 @@ Function *HotColdSplitting::outlineColdBlocks(Function &F,
Exit = (*PDT)[Exit]->getIDom()->getBlock();
}
if (ExitColdRegion) {
// Do not outline a region with only one block.
if (ValidColdRegion.size() == 1)
continue;
++NumColdSESEFound;
// Candidate for outlining. FIXME: Continue outlining.
// FIXME: Shouldn't need uniquing, debug isSingleEntrySingleExit
//std::sort(ValidColdRegion.begin(), ValidColdRegion.end());
auto last = std::unique(ValidColdRegion.begin(), ValidColdRegion.end());
ValidColdRegion.erase(last, ValidColdRegion.end());
return extractColdRegion(ValidColdRegion, DT, BFI, ORE);
}
}