Don't shrink live ranges after dead code elimination unless it is going to help.
In particular, don't repeatedly recompute the PIC base live range after rematerialization.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@129275 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/LiveRangeEdit.cpp b/lib/CodeGen/LiveRangeEdit.cpp
index b96575e..88ee457 100644
--- a/lib/CodeGen/LiveRangeEdit.cpp
+++ b/lib/CodeGen/LiveRangeEdit.cpp
@@ -203,6 +203,7 @@
SetVector<LiveInterval*,
SmallVector<LiveInterval*, 8>,
SmallPtrSet<LiveInterval*, 8> > ToShrink;
+ MachineRegisterInfo &MRI = VRM.getRegInfo();
for (;;) {
// Erase all dead defs.
@@ -236,8 +237,13 @@
continue;
LiveInterval &LI = LIS.getInterval(Reg);
- // Shrink read registers.
- if (MI->readsVirtualRegister(Reg))
+ // Shrink read registers, unless it is likely to be expensive and
+ // unlikely to change anything. We typically don't want to shrink the
+ // PIC base register that has lots of uses everywhere.
+ // Always shrink COPY uses that probably come from live range splitting.
+ if (MI->readsVirtualRegister(Reg) &&
+ (MI->isCopy() || MOI->isDef() || MRI.hasOneNonDBGUse(Reg) ||
+ LI.killedAt(Idx)))
ToShrink.insert(&LI);
// Remove defined value.
@@ -266,7 +272,7 @@
// Shrink just one live interval. Then delete new dead defs.
LiveInterval *LI = ToShrink.back();
ToShrink.pop_back();
- if (foldAsLoad(LI, Dead, VRM.getRegInfo(), LIS, TII))
+ if (foldAsLoad(LI, Dead, MRI, LIS, TII))
continue;
if (delegate_)
delegate_->LRE_WillShrinkVirtReg(LI->reg);
@@ -286,7 +292,7 @@
if (delegate_)
delegate_->LRE_DidCloneVirtReg(Dups.back()->reg, LI->reg);
}
- ConEQ.Distribute(&Dups[0], VRM.getRegInfo());
+ ConEQ.Distribute(&Dups[0], MRI);
}
}