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[RISCV] Don't add Zilsd pairing hints if part of the pair is reserved. #169538

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Merged
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Nov 25, 2025
+3 −5
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[RISCV] Don't add Zilsd pairing hints if part of the pair is reserved. #169538

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8 changes: 3 additions & 5 deletions llvm/lib/Target/RISCV/RISCVRegisterInfo.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -895,11 +895,9 @@ bool RISCVRegisterInfo::getRegAllocationHints(
// Check if this register matches the even/odd requirement
bool IsOdd = (RegNum % 2 != 0);

// Verify the pair register exists and is in the same register class
// TODO: Skip unallocatable registers: we need to prevent any of odd/even
// to be reserved, so if we need odd, we need to check if corresponding
// even is preserved, vice versa.
if ((WantOdd && IsOdd) || (!WantOdd && !IsOdd))
// Don't provide hints that are paired to a reserved register.
MCRegister Paired = PhysReg + (IsOdd ? -1 : 1);
if (WantOdd == IsOdd && !MRI->isReserved(Paired))
Hints.push_back(PhysReg);
}
}
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