================
@@ -4173,6 +4178,130 @@ bool SIRegisterInfo::getRegAllocationHints(Register
VirtReg,
}
}
+bool SIRegisterInfo::shouldApplyAntiHints(
+ const MachineFunction &MF, unsigned NumAllocatedVGPRs,
+ unsigned &MaxVGPRsForCurrentOccupancy) const {
+
+ const SIMachineFunctionInfo *MFI = MF.getInfo<SIMachineFunctionInfo>();
+ unsigned DynamicVGPRBlockSize = MFI->getDynamicVGPRBlockSize();
+ unsigned TargetOccupancy = MFI->getOccupancy();
+ unsigned CurrentOccupancy =
+ ST.getOccupancyWithNumVGPRs(NumAllocatedVGPRs, DynamicVGPRBlockSize);
+ MaxVGPRsForCurrentOccupancy =
+ ST.getMaxNumVGPRs(CurrentOccupancy, DynamicVGPRBlockSize);
+
+ LLVM_DEBUG(dbgs() << "anti-hints: " << NumAllocatedVGPRs
+ << " VGPRs allocated, target occupancy " << TargetOccupancy
+ << ", current occupancy " << CurrentOccupancy << '\n');
+
+ // If we are already at lowest occupancy, then there is no need to protect
+ // against occupancy regression.
+ if (CurrentOccupancy == 1)
+ return true;
+
+ // Set max VGPRs for target and current occupancy to early bail out if we are
+ // close to the limit.
+ unsigned MaxVGPRsCutOffForTargetOccupancy =
+ (ST.getMaxNumVGPRs(TargetOccupancy, DynamicVGPRBlockSize) * 80) / 100;
+ unsigned MaxVGPRsCutOffForCurrentOccupancy =
+ (MaxVGPRsForCurrentOccupancy * 95) / 100;
----------------
mssefat wrote:
I added the comments. For now, I would propose to keep them as internal
heuristics rather than adding cli options in this PR. The values were
hand-waved on a small benchmark but broader validation is still needed before
exposing them as the user tuning controls. If further benchmarking indicates
that users would benefit from adjusting them I can add hidden options in a
follow-up PR.
https://github.com/llvm/llvm-project/pull/218074
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