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Make the hasPHIKills flag a computed property.

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The VNInfo::HAS_PHI_KILL is only half supported. We precompute it in
LiveIntervalAnalysis, but it isn't properly updated by live range
splitting and functions like shrinkToUses().

It is only used in one place: RegisterCoalescer::removeCopyByCommutingDef().

This patch changes that function to use a new LiveIntervals::hasPHIKill()
function that computes the flag for a given value number.

llvm-svn: 161254
This commit is contained in:
Jakob Stoklund Olesen 2012-08-03 20:10:24 +00:00
parent 036c15bb42
commit 74dfaec8d7
3 changed files with 29 additions and 4 deletions
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4
include/llvm/CodeGen/LiveIntervalAnalysis.h
View File

@ -246,6 +246,10 @@ namespace llvm {
/// return NULL.
MachineBasicBlock *intervalIsInOneMBB(const LiveInterval &LI) const;
/// Returns true if VNI is killed by any PHI-def values in LI.
/// This may conservatively return true to avoid expensive computations.
bool hasPHIKill(const LiveInterval &LI, const VNInfo *VNI) const;
/// addKillFlags - Add kill flags to any instruction that kills a virtual
/// register.
void addKillFlags();

19
lib/CodeGen/LiveIntervalAnalysis.cpp
View File

@ -780,6 +780,25 @@ LiveIntervals::intervalIsInOneMBB(const LiveInterval &LI) const {
return MBB1 == MBB2 ? MBB1 : NULL;
}
bool
LiveIntervals::hasPHIKill(const LiveInterval &LI, const VNInfo *VNI) const {
for (LiveInterval::const_vni_iterator I = LI.vni_begin(), E = LI.vni_end();
I != E; ++I) {
const VNInfo *PHI = *I;
if (PHI->isUnused() || !PHI->isPHIDef())
continue;
const MachineBasicBlock *PHIMBB = getMBBFromIndex(PHI->def);
// Conservatively return true instead of scanning huge predecessor lists.
if (PHIMBB->pred_size() > 100)
return true;
for (MachineBasicBlock::const_pred_iterator
PI = PHIMBB->pred_begin(), PE = PHIMBB->pred_end(); PI != PE; ++PI)
if (VNI == LI.getVNInfoBefore(Indexes->getMBBEndIdx(*PI)))
return true;
}
return false;
}
float
LiveIntervals::getSpillWeight(bool isDef, bool isUse, unsigned loopDepth) {
// Limit the loop depth ridiculousness.

10
lib/CodeGen/RegisterCoalescer.cpp
View File

@ -494,6 +494,11 @@ bool RegisterCoalescer::hasOtherReachingDefs(LiveInterval &IntA,
LiveInterval &IntB,
VNInfo *AValNo,
VNInfo *BValNo) {
// If AValNo has PHI kills, conservatively assume that IntB defs can reach
// the PHI values.
if (LIS->hasPHIKill(IntA, AValNo))
return true;
for (LiveInterval::iterator AI = IntA.begin(), AE = IntA.end();
AI != AE; ++AI) {
if (AI->valno != AValNo) continue;
@ -558,10 +563,7 @@ bool RegisterCoalescer::removeCopyByCommutingDef(const CoalescerPair &CP,
// AValNo is the value number in A that defines the copy, A3 in the example.
VNInfo *AValNo = IntA.getVNInfoAt(CopyIdx.getRegSlot(true));
assert(AValNo && "COPY source not live");
// If other defs can reach uses of this def, then it's not safe to perform
// the optimization.
if (AValNo->isPHIDef() || AValNo->isUnused() || AValNo->hasPHIKill())
if (AValNo->isPHIDef() || AValNo->isUnused())
return false;
MachineInstr *DefMI = LIS->getInstructionFromIndex(AValNo->def);
if (!DefMI)