[llvm-commits] [llvm] r97688 - /llvm/trunk/lib/CodeGen/MachineCSE.cpp

[Evan Cheng]

Author: evancheng
Date: Wed Mar  3 17:59:08 2010
New Revision: 97688

URL: http://llvm.org/viewvc/llvm-project?rev=97688&view=rev
Log:
Fix a logic error. An instruction that has a live physical register def cannot be CSE'ed, but it *can* be used to replace a common subexpression.

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

Modified: llvm/trunk/lib/CodeGen/MachineCSE.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/MachineCSE.cpp?rev=97688&r1=97687&r2=97688&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/MachineCSE.cpp (original)
+++ llvm/trunk/lib/CodeGen/MachineCSE.cpp Wed Mar  3 17:59:08 2010
@@ -128,8 +128,6 @@
     if (TII->isMoveInstr(*MI, SrcReg, DstReg, SrcSubIdx, DstSubIdx) ||
         MI->isExtractSubreg() || MI->isInsertSubreg() || MI->isSubregToReg())
       continue;    
-    if (hasLivePhysRegDefUse(MI))
-      continue;
 
     bool FoundCSE = VNT.count(MI);
     if (!FoundCSE) {
@@ -138,6 +136,11 @@
         FoundCSE = VNT.count(MI);
     }
 
+    // If the instruction defines a physical register and the value *may* be
+    // used, then it's not safe to replace it with a common subexpression.
+    if (FoundCSE && hasLivePhysRegDefUse(MI))
+      FoundCSE = false;
+
     if (!FoundCSE) {
       VNT.insert(MI, CurrVN++);
       Exps.push_back(MI);