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Abstract the liveness checking in PHIElimination::SplitPHIEdges() to support

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both LiveVariables and LiveIntervals.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174850 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Cameron Zwarich 2013-02-10 23:29:49 +00:00
parent c3ba0a821b
commit 36f54480f8
1 changed files with 37 additions and 2 deletions
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39
lib/CodeGen/PHIElimination.cpp
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@ -75,6 +75,11 @@ namespace {
bool SplitPHIEdges(MachineFunction &MF, MachineBasicBlock &MBB, bool SplitPHIEdges(MachineFunction &MF, MachineBasicBlock &MBB,
MachineLoopInfo *MLI); MachineLoopInfo *MLI);
// These functions are temporary abstractions around LiveVariables and
// LiveIntervals, so they can go away when LiveVariables does.
bool isLiveIn(unsigned Reg, MachineBasicBlock *MBB);
bool isLiveOutPastPHIs(unsigned Reg, MachineBasicBlock *MBB);
typedef std::pair<unsigned, unsigned> BBVRegPair; typedef std::pair<unsigned, unsigned> BBVRegPair;
typedef DenseMap<BBVRegPair, unsigned> VRegPHIUse; typedef DenseMap<BBVRegPair, unsigned> VRegPHIUse;
@ -557,7 +562,7 @@ bool PHIElimination::SplitPHIEdges(MachineFunction &MF,
// there is a risk it may not be coalesced away. // there is a risk it may not be coalesced away.
// //
// If the copy would be a kill, there is no need to split the edge. // If the copy would be a kill, there is no need to split the edge.
if (!LV->isLiveOut(Reg, *PreMBB)) if (!isLiveOutPastPHIs(Reg, PreMBB))
continue; continue;
DEBUG(dbgs() << PrintReg(Reg) << " live-out before critical edge BB#" DEBUG(dbgs() << PrintReg(Reg) << " live-out before critical edge BB#"
@ -572,7 +577,7 @@ bool PHIElimination::SplitPHIEdges(MachineFunction &MF,
// is likely to be left after coalescing. If we are looking at a loop // is likely to be left after coalescing. If we are looking at a loop
// exiting edge, split it so we won't insert code in the loop, otherwise // exiting edge, split it so we won't insert code in the loop, otherwise
// don't bother. // don't bother.
bool ShouldSplit = !LV->isLiveIn(Reg, MBB); bool ShouldSplit = !isLiveIn(Reg, &MBB);
// Check for a loop exiting edge. // Check for a loop exiting edge.
if (!ShouldSplit && CurLoop != PreLoop) { if (!ShouldSplit && CurLoop != PreLoop) {
@ -599,3 +604,33 @@ bool PHIElimination::SplitPHIEdges(MachineFunction &MF,
} }
return Changed; return Changed;
} }
bool PHIElimination::isLiveIn(unsigned Reg, MachineBasicBlock *MBB) {
assert((LV || LIS) &&
"isLiveIn() requires either LiveVariables or LiveIntervals");
if (LIS)
return LIS->isLiveInToMBB(LIS->getInterval(Reg), MBB);
else
return LV->isLiveIn(Reg, *MBB);
}
bool PHIElimination::isLiveOutPastPHIs(unsigned Reg, MachineBasicBlock *MBB) {
assert((LV || LIS) &&
"isLiveOutPastPHIs() requires either LiveVariables or LiveIntervals");
// LiveVariables considers uses in PHIs to be in the predecessor basic block,
// so that a register used only in a PHI is not live out of the block. In
// contrast, LiveIntervals considers uses in PHIs to be on the edge rather than
// in the predecessor basic block, so that a register used only in a PHI is live
// out of the block.
if (LIS) {
const LiveInterval &LI = LIS->getInterval(Reg);
for (MachineBasicBlock::succ_iterator SI = MBB->succ_begin(),
SE = MBB->succ_end(); SI != SE; ++SI) {
if (LI.liveAt(LIS->getMBBStartIdx(*SI)))
return true;
}
return false;
} else {
return LV->isLiveOut(Reg, *MBB);
}
}