[AIEX] Bail out from waw rewriter for spilled register #361
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niwinanto
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abhinay-anubola,
abnikant,
andcarminati,
F-Stuckmann,
gbossu,
katerynamuts,
khallouh,
konstantinschwarz,
martien-de-jong,
SagarMaheshwari99 and
stephenneuendorffer
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| @@ -33,6 +33,7 @@ | |||
| #include "llvm/CodeGen/TargetSubtargetInfo.h" | |||
| #include "llvm/MC/MCRegister.h" | |||
| #include "llvm/Support/Debug.h" | |||
| #include "llvm/Support/ErrorHandling.h" | |||
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Is this include necessary?
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| # | ||
| # (c) Copyright 2025 Advanced Micro Devices, Inc. or its affiliates | ||
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| # Workaround WAW register renaming pass for llvm bug #48911. We must not crash here. |
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nit: Add a comment which register is now skipped due to being a spill register
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LGTM |
| @@ -253,7 +253,12 @@ bool AIEWawRegRewriter::renameMBBPhysRegs(const MachineBasicBlock *MBB) { | |||
| // WAW dependency resolution | |||
| if (LastVRegDef[Reg] != &MI) | |||
| continue; | |||
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| // See llvm bug #48911. | |||
| // Skip reassign if a register has originated from such split. | |||
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I would appreciate a brief inline explanation of 'such split' if possible/feasible.
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| // FIXME: Remove the workaround when bug #48911 is fixed. | ||
| if (VRM->getPreSplitReg(Reg)) { | ||
| continue; | ||
| } |
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I'm wondering if we shouldn't abort altogether? It seems dangerous to do further manipulations to the LiveRegMatrix if isn't up to date. Or is this really safe to just skip this register, but continue with the other ones?
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There is an upstream bug which stop us from unassigning the spilled register after greedy. So we bail out for such cases from aie-waw-rewriter pass.
llvm/llvm-project#48255