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Be more careful about choosing restore points when doing restore folding. This fixes some subtle miscompilations.

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llvm-svn: 66147
This commit is contained in:
Owen Anderson 2009-03-05 07:19:18 +00:00
parent c4f40d1f53
commit 744e33c12b
1 changed files with 28 additions and 5 deletions
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33
lib/CodeGen/PreAllocSplitting.cpp
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@ -38,10 +38,12 @@ using namespace llvm;
static cl::opt<int> PreSplitLimit("pre-split-limit", cl::init(-1), cl::Hidden);
static cl::opt<int> DeadSplitLimit("dead-split-limit", cl::init(-1), cl::Hidden);
static cl::opt<int> RestoreFoldLimit("restore-fold-limit", cl::init(-1), cl::Hidden);
STATISTIC(NumSplits, "Number of intervals split");
STATISTIC(NumRemats, "Number of intervals split by rematerialization");
STATISTIC(NumFolds, "Number of intervals split with spill folding");
STATISTIC(NumRestoreFolds, "Number of intervals split with restore folding");
STATISTIC(NumRenumbers, "Number of intervals renumbered into new registers");
STATISTIC(NumDeadSpills, "Number of dead spills removed");
@ -1013,15 +1015,32 @@ MachineInstr* PreAllocSplitting::FoldRestore(unsigned vreg,
MachineBasicBlock* MBB,
int SS,
SmallPtrSet<MachineInstr*, 4>& RefsInMBB) {
if ((int)RestoreFoldLimit != -1 && RestoreFoldLimit == NumRestoreFolds)
return 0;
// Go top down if RefsInMBB is empty.
if (RefsInMBB.empty())
return 0;
// Can't fold a restore between a call stack setup and teardown.
MachineBasicBlock::iterator FoldPt = Barrier;
while (FoldPt != MBB->getFirstTerminator() && !RefsInMBB.count(FoldPt)) {
++FoldPt;
// Advance from barrier to call frame teardown.
while (FoldPt != MBB->getFirstTerminator() &&
FoldPt->getOpcode() != TRI->getCallFrameDestroyOpcode()) {
if (RefsInMBB.count(FoldPt))
return 0;
++FoldPt;
}
if (FoldPt == MBB->getFirstTerminator())
return 0;
else
++FoldPt;
// Now find the restore point.
while (FoldPt != MBB->getFirstTerminator() && !RefsInMBB.count(FoldPt)) {
if (FoldPt->getOpcode() == TRI->getCallFrameSetupOpcode()) {
while (FoldPt != MBB->getFirstTerminator() &&
FoldPt->getOpcode() != TRI->getCallFrameDestroyOpcode()) {
@ -1031,8 +1050,11 @@ MachineInstr* PreAllocSplitting::FoldRestore(unsigned vreg,
++FoldPt;
}
++FoldPt;
}
if (FoldPt == MBB->getFirstTerminator())
return 0;
}
++FoldPt;
}
if (FoldPt == MBB->getFirstTerminator())
@ -1054,7 +1076,7 @@ MachineInstr* PreAllocSplitting::FoldRestore(unsigned vreg,
if (FMI) {
LIs->ReplaceMachineInstrInMaps(FoldPt, FMI);
FMI = MBB->insert(MBB->erase(FoldPt), FMI);
++NumFolds;
++NumRestoreFolds;
}
return FMI;
@ -1171,6 +1193,7 @@ bool PreAllocSplitting::SplitRegLiveInterval(LiveInterval *LI) {
if (MachineInstr* LMI = FoldRestore(CurrLI->reg, RC, Barrier,
BarrierMBB, SS, RefsInMBB)) {
RestorePt = LMI;
RestoreIndex = LIs->getInstructionIndex(RestorePt);
FoldedRestore = true;
} else {
TII->loadRegFromStackSlot(*BarrierMBB, RestorePt, CurrLI->reg, SS, RC);