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Minor optimizations. DenseMap::begin() is surprisingly slow on an empty map.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103940 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen 2010-05-17 15:30:37 +00:00
parent 548643c573
commit f3ea06b108
1 changed files with 7 additions and 8 deletions
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15
lib/CodeGen/RegAllocFast.cpp
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@ -267,6 +267,7 @@ void RAFast::spillVirtReg(MachineBasicBlock::iterator MI,
/// 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 @@ void RAFast::allocVirtReg(MachineInstr *MI, LiveRegEntry &LRE, unsigned Hint) {
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);
}