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Temporarily add a flag to make it easier to compare the new-style ARM if

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conversion heuristics to the old-style ones.

llvm-svn: 115239
This commit is contained in:
Owen Anderson 2010-09-30 23:48:38 +00:00
parent 45de3f6747
commit 918c558636
1 changed files with 19 additions and 0 deletions
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19
lib/Target/ARM/ARMBaseInstrInfo.cpp
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@ -40,6 +40,10 @@ static cl::opt<bool>
EnableARM3Addr("enable-arm-3-addr-conv", cl::Hidden,
cl::desc("Enable ARM 2-addr to 3-addr conv"));
static cl::opt<bool>
OldARMIfConv("old-arm-if-conversion", cl::Hidden,
cl::desc("Use old-style ARM if-conversion heuristics"));
ARMBaseInstrInfo::ARMBaseInstrInfo(const ARMSubtarget& STI)
: TargetInstrInfoImpl(ARMInsts, array_lengthof(ARMInsts)),
Subtarget(STI) {
@ -1201,6 +1205,16 @@ bool ARMBaseInstrInfo::isProfitableToIfCvt(MachineBasicBlock &MBB,
if (!NumInstrs)
return false;
// Use old-style heuristics
if (OldARMIfConv) {
if (Subtarget.getCPUString() == "generic")
// Generic (and overly aggressive) if-conversion limits for testing.
return NumInstrs <= 10;
else if (Subtarget.hasV7Ops())
return NumInstrs <= 3;
return NumInstrs <= 2;
}
// Attempt to estimate the relative costs of predication versus branching.
float UnpredCost = Probability * NumInstrs;
UnpredCost += 1.0; // The branch itself
@ -1216,6 +1230,11 @@ bool ARMBaseInstrInfo::
isProfitableToIfCvt(MachineBasicBlock &TMBB, unsigned NumT,
MachineBasicBlock &FMBB, unsigned NumF,
float Probability) const {
// Use old-style if-conversion heuristics
if (OldARMIfConv) {
return NumT && NumF && NumT <= 2 && NumF <= 2;
}
if (!NumT || !NumF)
return false;