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[RegisterClassInfo] Return non-zero for RC without allocatable reg

Authored by jsji on Jan 5 2021, 7:37 AM.

Description

[RegisterClassInfo] Return non-zero for RC without allocatable reg

In some case, the RC may have 0 allocatable reg.
eg: VRSAVERC in PowerPC, which has only 1 reg, but it is also reserved.

The curreent implementation will keep calling the computePSetLimit because
getRegPressureSetLimit assume computePSetLimit will return a non-zero value.

The fix simply early return the value from TableGen for such special case.

Reviewed By: RKSimon

Differential Revision: https://reviews.llvm.org/D92907

Details

Committed
jsjiJan 5 2021, 8:18 AM
Reviewer
RKSimon
Differential Revision
D92907: [RegisterClassInfo] Return non-zero for RC without allocatable reg
Parents
rG51d5991f04dd: [Clang] Add AArch64 VCMLA LANE variants.
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