[PATCH] D110170: [InstCombine] fold cast of right-shift if high bits are not demanded

[Sanjay Patel via Phabricator via llvm-commits]

spatel added a comment.

In D110170#3019762 <https://reviews.llvm.org/D110170#3019762>, @uabelho wrote:

> In D110170#3019717 <https://reviews.llvm.org/D110170#3019717>, @uabelho wrote:
>
>> Just a heads-up, I'm seeing timeouts again now with "2nd try" commited.
>>
>> I'll see if I can pull out a reproducer working on main too.
>
> Ok:
>
>   opt -o /dev/null -passes='instcombine' hang.ll
>
> with hang.ll being
>
>   target datalayout = "n32"
>   
>   define i32 @f_t15_t01_t09(i40 %x) {
>   entry:
>     store i40 %x, i40* undef, align 1
>     %0 = load i40, i40* undef, align 1
>     %1 = add i40 %0, 2147483647
>     %2 = select i1 undef, i40 %1, i40 %0
>     %downscale = ashr i40 %2, 31
>     %resize = trunc i40 %downscale to i16
>     %resize1 = sext i16 %resize to i32
>     %upscale = shl i32 %resize1, 31
>     ret i32 %upscale
>   }

Thanks! I'll step into this in the debugger now.
Let me know if I should revert.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D110170/new/

https://reviews.llvm.org/D110170