Tidy some #includes and forward-declarations, and move the C binding code

[oota-llvm.git] / lib / CodeGen / RegisterScavenging.cpp

diff --git a/lib/CodeGen/RegisterScavenging.cpp b/lib/CodeGen/RegisterScavenging.cpp
index 3eefedadf29e1d7e7bf2a67a62345604ac822cb4..43b3fb642635149d4a00574b5e35266ea8a01d83 100644 (file)
--- a/lib/CodeGen/RegisterScavenging.cpp
+++ b/lib/CodeGen/RegisterScavenging.cpp
@@ -242,8 +242,18 @@ unsigned RegScavenger::FindUnusedReg(const TargetRegisterClass *RC) const {
   return 0;
 }
 
+/// getRegsAvailable - Return all available registers in the register class
+/// in Mask.
+void RegScavenger::getRegsAvailable(const TargetRegisterClass *RC,
+                                    BitVector &Mask) {
+  for (TargetRegisterClass::iterator I = RC->begin(), E = RC->end();
+       I != E; ++I)
+    if (!isAliasUsed(*I))
+      Mask.set(*I);
+}
+
 /// findSurvivorReg - Return the candidate register that is unused for the
-/// longest after MBBI. UseMI is set to the instruction where the search
+/// longest after StargMII. UseMI is set to the instruction where the search
 /// stopped.
 ///
 /// No more than InstrLimit instructions are inspected.
@@ -329,13 +339,16 @@ unsigned RegScavenger::scavengeRegister(const TargetRegisterClass *RC,
       Candidates.reset(MO.getReg());
   }
 
+  // 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;
+
   // Find the register whose use is furthest away.
   MachineBasicBlock::iterator UseMI;
   unsigned SReg = findSurvivorReg(I, Candidates, 25, UseMI);
 
-  // If we found an unused register there is no reason to spill it. We have
-  // probably found a callee-saved register that has been saved in the
-  // prologue, but happens to be unused at this point.
+  // If we found an unused register there is no reason to spill it.
   if (!isAliasUsed(SReg))
     return SReg;