[llvm-commits] [llvm] r72755 - /llvm/trunk/lib/CodeGen/LiveVariables.cpp

[Evan Cheng]

Author: evancheng
Date: Wed Jun  3 00:15:46 2009
New Revision: 72755

URL: http://llvm.org/viewvc/llvm-project?rev=72755&view=rev
Log:
If there is a def of a super-register followed by a use of a sub-register, do *not* add an implicit def of the sub-register. e.g.
EAX = ..., AX<imp-def>
..
    = AX

This creates a double-def. Apparently this used to be necessary but is no longer needed.

Thanks to Anton for pointing this out. Anton, I cannot create a test case without your uncommitted ARM patches. Please check in a test case for me.

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

Modified: llvm/trunk/lib/CodeGen/LiveVariables.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/LiveVariables.cpp?rev=72755&r1=72754&r2=72755&view=diff

==============================================================================
--- llvm/trunk/lib/CodeGen/LiveVariables.cpp (original)
+++ llvm/trunk/lib/CodeGen/LiveVariables.cpp Wed Jun  3 00:15:46 2009
@@ -242,20 +242,6 @@
     }
   }
 
-  // There was an earlier def of a super-register. Add implicit def to that MI.
-  //
-  //   A: EAX = ...
-  //   B: ... = AX
-  //
-  // Add implicit def to A if there isn't a use of AX (or EAX) before B.
-  if (!PhysRegUse[Reg]) {
-    MachineInstr *Def = PhysRegDef[Reg];
-    if (Def && !Def->modifiesRegister(Reg))
-      Def->addOperand(MachineOperand::CreateReg(Reg,
-                                                true  /*IsDef*/,
-                                                true  /*IsImp*/));
-  }
-  
   // Remember this use.
   PhysRegUse[Reg]  = MI;
   for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);