[llvm-commits] [llvm] r127049 - in /llvm/trunk: include/llvm/CodeGen/RegisterScavenging.h lib/CodeGen/RegisterScavenging.cpp

[Jim Grosbach]

Author: grosbach
Date: Fri Mar  4 18:20:19 2011
New Revision: 127049

URL: http://llvm.org/viewvc/llvm-project?rev=127049&view=rev
Log:
Teach the register scavenger to take subregs into account when finding a free register.

Modified:
    llvm/trunk/include/llvm/CodeGen/RegisterScavenging.h
    llvm/trunk/lib/CodeGen/RegisterScavenging.cpp

Modified: llvm/trunk/include/llvm/CodeGen/RegisterScavenging.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/RegisterScavenging.h?rev=127049&r1=127048&r2=127049&view=diff
==============================================================================
--- llvm/trunk/include/llvm/CodeGen/RegisterScavenging.h (original)
+++ llvm/trunk/include/llvm/CodeGen/RegisterScavenging.h Fri Mar  4 18:20:19 2011
@@ -100,7 +100,7 @@
 
   /// getRegsAvailable - Return all available registers in the register class
   /// in Mask.
-  void getRegsAvailable(const TargetRegisterClass *RC, BitVector &Mask);
+  BitVector getRegsAvailable(const TargetRegisterClass *RC);
 
   /// FindUnusedReg - Find a unused register of the specified register class.
   /// Return 0 if none is found.

Modified: llvm/trunk/lib/CodeGen/RegisterScavenging.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/RegisterScavenging.cpp?rev=127049&r1=127048&r2=127049&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/RegisterScavenging.cpp (original)
+++ llvm/trunk/lib/CodeGen/RegisterScavenging.cpp Fri Mar  4 18:20:19 2011
@@ -241,12 +241,13 @@
 
 /// getRegsAvailable - Return all available registers in the register class
 /// in Mask.
-void RegScavenger::getRegsAvailable(const TargetRegisterClass *RC,
-                                    BitVector &Mask) {
+BitVector RegScavenger::getRegsAvailable(const TargetRegisterClass *RC) {
+  BitVector Mask(TRI->getNumRegs());
   for (TargetRegisterClass::iterator I = RC->begin(), E = RC->end();
        I != E; ++I)
     if (!isAliasUsed(*I))
       Mask.set(*I);
+  return Mask;
 }
 
 /// findSurvivorReg - Return the candidate register that is unused for the
@@ -335,9 +336,13 @@
   }
 
   // Try to find a register that's unused if there is one, as then we won't
-  // have to spill.
-  if ((Candidates & RegsAvailable).any())
-     Candidates &= RegsAvailable;
+  // have to spill. Search explicitly rather than masking out based on
+  // RegsAvailable, as RegsAvailable does not take aliases into account.
+  // That's what getRegsAvailable() is for.
+  BitVector Available = getRegsAvailable(RC);
+
+  if ((Candidates & Available).any())
+     Candidates &= Available;
 
   // Find the register whose use is furthest away.
   MachineBasicBlock::iterator UseMI;