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[MachineScheduler] Fix physreg dependencies of ExitSU #123541
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05cca1b
[MachineScheduler] Fix physreg dependencies of ExitSU
s-barannikov 8b87e2f
Comment the check
s-barannikov d709f4b
Update remaining tests
s-barannikov 806fa90
Update LSR test
s-barannikov b7cfe8b
Try to improve FIXME
s-barannikov e51732a
Remove FIXME as it turned out that there is nothing to fix
s-barannikov 38cf1e4
Merge remote-tracking branch 'upstream/main' into misched/exit-su-dep
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Original file line number | Diff line number | Diff line change |
---|---|---|
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@@ -209,13 +209,25 @@ void ScheduleDAGInstrs::addSchedBarrierDeps() { | |
ExitSU.setInstr(ExitMI); | ||
// Add dependencies on the defs and uses of the instruction. | ||
if (ExitMI) { | ||
const MCInstrDesc &MIDesc = ExitMI->getDesc(); | ||
for (const MachineOperand &MO : ExitMI->all_uses()) { | ||
unsigned OpIdx = MO.getOperandNo(); | ||
Register Reg = MO.getReg(); | ||
if (Reg.isPhysical()) { | ||
// addPhysRegDataDeps uses the provided operand index to retrieve | ||
// the operand use cycle from the scheduling model. If the operand | ||
// is "fake" (e.g., an operand of a call instruction used to pass | ||
// an argument to the called function.), the scheduling model may not | ||
// have an entry for it. If this is the case, pass -1 as operand index, | ||
// which will cause addPhysRegDataDeps to add an artificial dependency. | ||
// FIXME: Using hasImplicitUseOfPhysReg here is inaccurate as it misses | ||
// aliases. When fixing, make sure to update addPhysRegDataDeps, too. | ||
bool IsRealUse = OpIdx < MIDesc.getNumOperands() || | ||
MIDesc.hasImplicitUseOfPhysReg(Reg); | ||
for (MCRegUnit Unit : TRI->regunits(Reg)) | ||
Uses.insert(PhysRegSUOper(&ExitSU, -1, Unit)); | ||
Uses.insert(PhysRegSUOper(&ExitSU, IsRealUse ? OpIdx : -1, Unit)); | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. This is where an operand index gets a negative value. There is one more place at the end of this function. |
||
} else if (Reg.isVirtual() && MO.readsReg()) { | ||
addVRegUseDeps(&ExitSU, MO.getOperandNo()); | ||
addVRegUseDeps(&ExitSU, OpIdx); | ||
} | ||
} | ||
} | ||
|
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Comment this usage. I'm assuming getting this accurate isn't required for correctness?
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MIDesc.hasImplicitUseOfPhysReg also looks buggy to me. It doesn't have the MCRI argument like hasImplicitDefOfPhysReg, so it will miss any aliases
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As far as I'm aware, getting this accurate isn't required for correctness. My motivation for fixing this was to move comparisons away from branches if the latency between them is high (which is true on my target).
Good point, I'll add a FIXME.