[llvm-commits] [llvm] r103940 - /llvm/trunk/lib/CodeGen/RegAllocFast.cpp

[Jakob Stoklund Olesen]

Author: stoklund
Date: Mon May 17 10:30:37 2010
New Revision: 103940

URL: http://llvm.org/viewvc/llvm-project?rev=103940&view=rev
Log:
Minor optimizations. DenseMap::begin() is surprisingly slow on an empty map.

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

Modified: llvm/trunk/lib/CodeGen/RegAllocFast.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/RegAllocFast.cpp?rev=103940&r1=103939&r2=103940&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/RegAllocFast.cpp (original)
+++ llvm/trunk/lib/CodeGen/RegAllocFast.cpp Mon May 17 10:30:37 2010
@@ -267,6 +267,7 @@
 
 /// spillAll - Spill all dirty virtregs without killing them.
 void RAFast::spillAll(MachineInstr *MI) {
+  if (LiveVirtRegs.empty()) return;
   isBulkSpilling = true;
   for (LiveRegMap::iterator i = LiveVirtRegs.begin(),
        e = LiveVirtRegs.end(); i != e; ++i)
@@ -471,17 +472,15 @@
   unsigned BestReg = 0, BestCost = spillImpossible;
   for (TargetRegisterClass::iterator I = AOB; I != AOE; ++I) {
     unsigned Cost = calcSpillCost(*I);
-    if (Cost < BestCost) {
-      BestReg = *I;
-      BestCost = Cost;
-      if (Cost == 0) break;
-    }
+    // Cost is 0 when all aliases are already disabled.
+    if (Cost == 0)
+      return assignVirtToPhysReg(LRE, *I);
+    if (Cost < BestCost)
+      BestReg = *I, BestCost = Cost;
   }
 
   if (BestReg) {
-    // BestCost is 0 when all aliases are already disabled.
-    if (BestCost)
-      definePhysReg(MI, BestReg, regFree);
+    definePhysReg(MI, BestReg, regFree);
     return assignVirtToPhysReg(LRE, BestReg);
   }