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Work around a coalescer bug.

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The coalescer can in very rare cases leave too large live intervals around after
rematerializing cheap-as-a-move instructions.

Linear scan doesn't really care, but live range splitting gets very confused
when a live range is killed by a ghost instruction.

I will fix this properly in the coalescer after 2.9 branches.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127096 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen 2011-03-05 18:33:49 +00:00
parent 4faa0e1952
commit 2b0f9e73d8
2 changed files with 23 additions and 4 deletions
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25
lib/CodeGen/SplitKit.cpp
View File

@ -81,7 +81,20 @@ void SplitAnalysis::analyzeUses() {
UsingBlocks[MBB]++;
}
array_pod_sort(UseSlots.begin(), UseSlots.end());
calcLiveBlockInfo();
// Compute per-live block info.
if (!calcLiveBlockInfo()) {
// FIXME: calcLiveBlockInfo found inconsistencies in the live range.
// I am looking at you, SimpleRegisterCoalescing!
DEBUG(dbgs() << "*** Fixing inconsistent live interval! ***\n");
const_cast<LiveIntervals&>(LIS)
.shrinkToUses(const_cast<LiveInterval*>(CurLI));
LiveBlocks.clear();
bool fixed = calcLiveBlockInfo();
(void)fixed;
assert(fixed && "Couldn't fix broken live interval");
}
DEBUG(dbgs() << " counted "
<< UsingInstrs.size() << " instrs, "
<< UsingBlocks.size() << " blocks.\n");
@ -89,9 +102,9 @@ void SplitAnalysis::analyzeUses() {
/// calcLiveBlockInfo - Fill the LiveBlocks array with information about blocks
/// where CurLI is live.
void SplitAnalysis::calcLiveBlockInfo() {
bool SplitAnalysis::calcLiveBlockInfo() {
if (CurLI->empty())
return;
return true;
LiveInterval::const_iterator LVI = CurLI->begin();
LiveInterval::const_iterator LVE = CurLI->end();
@ -154,6 +167,11 @@ void SplitAnalysis::calcLiveBlockInfo() {
BI.LiveThrough = !hasGap && BI.LiveIn && BI.LiveOut;
LiveBlocks.push_back(BI);
// FIXME: This should never happen. The live range stops or starts without a
// corresponding use. An earlier pass did something wrong.
if (!BI.LiveThrough && !BI.Uses)
return false;
// LVI is now at LVE or LVI->end >= Stop.
if (LVI == LVE)
break;
@ -168,6 +186,7 @@ void SplitAnalysis::calcLiveBlockInfo() {
else
MFI = LIS.getMBBFromIndex(LVI->start);
}
return true;
}
bool SplitAnalysis::isOriginalEndpoint(SlotIndex Idx) const {

2
lib/CodeGen/SplitKit.h
View File

@ -103,7 +103,7 @@ private:
void analyzeUses();
/// calcLiveBlockInfo - Compute per-block information about CurLI.
void calcLiveBlockInfo();
bool calcLiveBlockInfo();
/// canAnalyzeBranch - Return true if MBB ends in a branch that can be
/// analyzed.