[PATCH] D130932: [MIPS] Expose the ZERO register as a constant physical register

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added a comment.

In D130932#3691969 <https://reviews.llvm.org/D130932#3691969>, @MaskRay wrote:

> It seems not so easy to construct a test. I've tried
>
>   declare i64 @llvm.read_register.i64(metadata)
>    
>   define i64 @get_gp() {
>     %1 = call i64 @llvm.read_register.i64(metadata !0)
>     %2 = call i64 @llvm.read_register.i64(metadata !0)
>     %sub = sub i64 %1, %2
>     ret i64 %sub
>   }
>    
>   !0 = !{!"$28"}
>
> which doesn't have benefit in another target which has implemented isConstantPhysReg.

Probably should try for a mir test


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  https://reviews.llvm.org/D130932/new/

https://reviews.llvm.org/D130932