Make the hasPHIKills flag a computed property.
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.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@161254 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/LiveIntervalAnalysis.cpp b/lib/CodeGen/LiveIntervalAnalysis.cpp
index 31f938e..54d6655 100644
--- a/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -780,6 +780,25 @@
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.
diff --git a/lib/CodeGen/RegisterCoalescer.cpp b/lib/CodeGen/RegisterCoalescer.cpp
index 349fcde..ebac8f1 100644
--- a/lib/CodeGen/RegisterCoalescer.cpp
+++ b/lib/CodeGen/RegisterCoalescer.cpp
@@ -494,6 +494,11 @@
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 @@
// 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)