[llvm-commits] [llvm] r129275 - /llvm/trunk/lib/CodeGen/LiveRangeEdit.cpp

[Jakob Stoklund Olesen]

Author: stoklund
Date: Mon Apr 11 10:00:39 2011
New Revision: 129275

URL: http://llvm.org/viewvc/llvm-project?rev=129275&view=rev
Log:
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.

Modified:
    llvm/trunk/lib/CodeGen/LiveRangeEdit.cpp

Modified: llvm/trunk/lib/CodeGen/LiveRangeEdit.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/LiveRangeEdit.cpp?rev=129275&r1=129274&r2=129275&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/LiveRangeEdit.cpp (original)
+++ llvm/trunk/lib/CodeGen/LiveRangeEdit.cpp Mon Apr 11 10:00:39 2011
@@ -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);
   }
 }