[llvm-commits] [llvm] r161461 - /llvm/trunk/lib/Target/X86/X86InstrInfo.cpp

[Jakob Stoklund Olesen]

Author: stoklund
Date: Tue Aug  7 19:40:47 2012
New Revision: 161461

URL: http://llvm.org/viewvc/llvm-project?rev=161461&view=rev
Log:
Don't scan physreg use-def chains looking for a PIC base.

We can't rematerialize a PIC base after register allocation anyway, and
scanning physreg use-def chains is very expensive in a function with
many calls.

<rdar://problem/12047515>

Modified:
    llvm/trunk/lib/Target/X86/X86InstrInfo.cpp

Modified: llvm/trunk/lib/Target/X86/X86InstrInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86InstrInfo.cpp?rev=161461&r1=161460&r2=161461&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86InstrInfo.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86InstrInfo.cpp Tue Aug  7 19:40:47 2012
@@ -1463,6 +1463,9 @@
 /// regIsPICBase - Return true if register is PIC base (i.e.g defined by
 /// X86::MOVPC32r.
 static bool regIsPICBase(unsigned BaseReg, const MachineRegisterInfo &MRI) {
+  // Don't waste compile time scanning use-def chains of physregs.
+  if (!TargetRegisterInfo::isVirtualRegister(BaseReg))
+    return false;
   bool isPICBase = false;
   for (MachineRegisterInfo::def_iterator I = MRI.def_begin(BaseReg),
          E = MRI.def_end(); I != E; ++I) {
@@ -1520,16 +1523,7 @@
           return false;
         const MachineFunction &MF = *MI->getParent()->getParent();
         const MachineRegisterInfo &MRI = MF.getRegInfo();
-        bool isPICBase = false;
-        for (MachineRegisterInfo::def_iterator I = MRI.def_begin(BaseReg),
-               E = MRI.def_end(); I != E; ++I) {
-          MachineInstr *DefMI = I.getOperand().getParent();
-          if (DefMI->getOpcode() != X86::MOVPC32r)
-            return false;
-          assert(!isPICBase && "More than one PIC base?");
-          isPICBase = true;
-        }
-        return isPICBase;
+        return regIsPICBase(BaseReg, MRI);
       }
       return false;
     }