Dead code elimination may separate the live interval into multiple connected components.
I have convinced myself that it can only happen when a phi value dies. When it
happens, allocate new virtual registers for the components.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127827 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/LiveIntervalAnalysis.cpp b/lib/CodeGen/LiveIntervalAnalysis.cpp
index f2bf917..c47c839 100644
--- a/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -746,7 +746,7 @@
/// shrinkToUses - After removing some uses of a register, shrink its live
/// range to just the remaining uses. This method does not compute reaching
/// defs for new uses, and it doesn't remove dead defs.
-void LiveIntervals::shrinkToUses(LiveInterval *li,
+bool LiveIntervals::shrinkToUses(LiveInterval *li,
SmallVectorImpl<MachineInstr*> *dead) {
DEBUG(dbgs() << "Shrink: " << *li << '\n');
assert(TargetRegisterInfo::isVirtualRegister(li->reg)
@@ -835,6 +835,7 @@
}
// Handle dead values.
+ bool CanSeparate = false;
for (LiveInterval::vni_iterator I = li->vni_begin(), E = li->vni_end();
I != E; ++I) {
VNInfo *VNI = *I;
@@ -848,6 +849,8 @@
// This is a dead PHI. Remove it.
VNI->setIsUnused(true);
NewLI.removeRange(*LII);
+ DEBUG(dbgs() << "Dead PHI at " << VNI->def << " may separate interval\n");
+ CanSeparate = true;
} else {
// This is a dead def. Make sure the instruction knows.
MachineInstr *MI = getInstructionFromIndex(VNI->def);
@@ -863,6 +866,7 @@
// Move the trimmed ranges back.
li->ranges.swap(NewLI.ranges);
DEBUG(dbgs() << "Shrunk: " << *li << '\n');
+ return CanSeparate;
}