[llvm-commits] [llvm] r148779 - /llvm/trunk/lib/CodeGen/TwoAddressInstructionPass.cpp

[Jakob Stoklund Olesen]

Author: stoklund
Date: Mon Jan 23 22:44:01 2012
New Revision: 148779

URL: http://llvm.org/viewvc/llvm-project?rev=148779&view=rev
Log:
Preserve <def,undef> flags in CoalesceExtSubRegs.

This won't have an effect until EliminateRegSequences() starts setting
the undef flags.

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

Modified: llvm/trunk/lib/CodeGen/TwoAddressInstructionPass.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/TwoAddressInstructionPass.cpp?rev=148779&r1=148778&r2=148779&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/TwoAddressInstructionPass.cpp (original)
+++ llvm/trunk/lib/CodeGen/TwoAddressInstructionPass.cpp Mon Jan 23 22:44:01 2012
@@ -1728,8 +1728,10 @@
         CanCoalesce = false;
         break;
       }
-      // Keep track of one of the uses.
-      SomeMI = UseMI;
+      // Keep track of one of the uses.  Preferably the first one which has a
+      // <def,undef> flag.
+      if (!SomeMI || UseMI->getOperand(0).isUndef())
+        SomeMI = UseMI;
     }
     if (!CanCoalesce)
       continue;
@@ -1738,7 +1740,9 @@
     MachineInstr *CopyMI = BuildMI(*SomeMI->getParent(), SomeMI,
                                    SomeMI->getDebugLoc(),
                                    TII->get(TargetOpcode::COPY))
-      .addReg(DstReg, RegState::Define, NewDstSubIdx)
+      .addReg(DstReg, RegState::Define |
+                      getUndefRegState(SomeMI->getOperand(0).isUndef()),
+              NewDstSubIdx)
       .addReg(SrcReg, 0, NewSrcSubIdx);
 
     // Remove all the old extract instructions.