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Use a smallvector for inactiveCounts and initialize it lazily

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instead of init'ing it maximally to zeros on entry.  getFreePhysReg
is pretty hot and only a few elements are typically used.  This speeds
up linscan by 5% on 176.gcc.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@47631 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2008-02-26 22:08:41 +00:00
parent e6d088acc9
commit fe42462164
1 changed files with 10 additions and 4 deletions
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14
lib/CodeGen/RegAllocLinearScan.cpp
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@ -839,7 +839,7 @@ void RALinScan::assignRegOrStackSlotAtInterval(LiveInterval* cur)
/// getFreePhysReg - return a free physical register for this virtual register
/// interval if we have one, otherwise return 0.
unsigned RALinScan::getFreePhysReg(LiveInterval *cur) {
std::vector<unsigned> inactiveCounts(tri_->getNumRegs(), 0);
SmallVector<unsigned, 256> inactiveCounts;
unsigned MaxInactiveCount = 0;
const TargetRegisterClass *RC = reginfo_->getRegClass(cur->reg);
@ -856,6 +856,8 @@ unsigned RALinScan::getFreePhysReg(LiveInterval *cur) {
const TargetRegisterClass *RegRC = reginfo_->getRegClass(reg);
if (RelatedRegClasses.getLeaderValue(RegRC) == RCLeader) {
reg = vrm_->getPhys(reg);
if (inactiveCounts.size() <= reg)
inactiveCounts.resize(reg+1);
++inactiveCounts[reg];
MaxInactiveCount = std::max(MaxInactiveCount, inactiveCounts[reg]);
}
@ -882,10 +884,13 @@ unsigned RALinScan::getFreePhysReg(LiveInterval *cur) {
for (; I != E; ++I)
if (prt_->isRegAvail(*I)) {
FreeReg = *I;
FreeRegInactiveCount = inactiveCounts[FreeReg];
if (FreeReg < inactiveCounts.size())
FreeRegInactiveCount = inactiveCounts[FreeReg];
else
FreeRegInactiveCount = 0;
break;
}
// If there are no free regs, or if this reg has the max inactive count,
// return this register.
if (FreeReg == 0 || FreeRegInactiveCount == MaxInactiveCount) return FreeReg;
@ -896,7 +901,8 @@ unsigned RALinScan::getFreePhysReg(LiveInterval *cur) {
// reevaluated now.
for (; I != E; ++I) {
unsigned Reg = *I;
if (prt_->isRegAvail(Reg) && FreeRegInactiveCount < inactiveCounts[Reg]) {
if (prt_->isRegAvail(Reg) && Reg < inactiveCounts.size() &&
FreeRegInactiveCount < inactiveCounts[Reg]) {
FreeReg = Reg;
FreeRegInactiveCount = inactiveCounts[Reg];
if (FreeRegInactiveCount == MaxInactiveCount)