[PATCH] D80485: [DAGCombiner][PowerPC] Remove isMulhCheaperThanMulShift TLI hook. Use isOperationLegalOrCustom directly instead.

[Piotr Sobczak via Phabricator via llvm-commits]

piotr added a comment.

In D80485#2342195 <https://reviews.llvm.org/D80485#2342195>, @amyk wrote:

> In D80485#2341858 <https://reviews.llvm.org/D80485#2341858>, @piotr wrote:
>
>> Hi! This commit causes problems for AMDGPU backend - see attached file F13392080: repro.ll <https://reviews.llvm.org/F13392080>. Any ideas before I start investigating this in detail?
>>
>> LLVM ERROR: Cannot select: t56: i16 = mulhs t42, Constant:i16<-32509>
>>
>>   t42: i16 = truncate t67
>>     t67: i32 = add t66, t28
>>       t66: i32 = add t37, t34
>>         t37: i32 = shl nuw nsw t12, Constant:i32<13>
>>           t12: i32,ch = CopyFromReg t0, Register:i32 %5
>>             t11: i32 = Register %5
>>           t36: i32 = Constant<13>
>>         t34: i32 = shl nuw nsw t10, Constant:i32<7>
>>           t10: i32,ch = CopyFromReg t0, Register:i32 %4
>>             t9: i32 = Register %4
>>           t26: i32 = Constant<7>
>>       t28: i32 = add t16, t27
>>         t16: i32,ch = CopyFromReg t0, Register:i32 %7
>>           t15: i32 = Register %7
>>         t27: i32 = shl t8, Constant:i32<7>
>>           t8: i32,ch = CopyFromReg t0, Register:i32 %3
>>             t7: i32 = Register %3
>>           t26: i32 = Constant<7>
>>   t52: i16 = Constant<-32509>
>
> Hi, I agree with the suggestion by @dmgreen. Could you see if that works?

Thanks for the suggestion - will try that.


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