InstCombine should fold frexp of select to select of frexp

[arsenm]

If one of the select operands is a constant, we generally push operations through to select on the result.

define float @src(float %x, i1 %bool) {
  %select = select i1 %bool, float 1.000000e+00, float %x
  %frexp = tail call { float, i32 } @llvm.frexp.f32.i32(float %select)
  %frexp.0 = extractvalue { float, i32 } %frexp, 0
  ret float %frexp.0
}

define float @tgt(float %x, i1 %bool) {
  %frexp = tail call { float, i32 } @llvm.frexp.f32.i32(float %x)
  %frexp.0 = extractvalue { float, i32 } %frexp, 0
  %select = select i1 %bool, float 5.000000e-01, float %frexp.0
  ret float %select
}

This case is somewhat complicated by the extractvalue. The combine should be rooted at a hasOneUse extractvalue (frexp), 0

[llvmbot]

Hi!

This issue may be a good introductory issue for people new to working on LLVM. If you would like to work on this issue, your first steps are:

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3. Fix the issue locally.
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[llvmbot]

@llvm/issue-subscribers-good-first-issue

Author: Matt Arsenault (arsenm)

If one of the select operands is a constant, we generally push operations through to select on the result.

define float @<!-- -->src(float %x, i1 %bool) {
  %select = select i1 %bool, float 1.000000e+00, float %x
  %frexp = tail call { float, i32 } @<!-- -->llvm.frexp.f32.i32(float %select)
  %frexp.0 = extractvalue { float, i32 } %frexp, 0
  ret float %frexp.0
}

define float @<!-- -->tgt(float %x, i1 %bool) {
  %frexp = tail call { float, i32 } @<!-- -->llvm.frexp.f32.i32(float %x)
  %frexp.0 = extractvalue { float, i32 } %frexp, 0
  %select = select i1 %bool, float 5.000000e-01, float %frexp.0
  ret float %select
}

This case is somewhat complicated by the extractvalue. The combine should be rooted at a hasOneUse extractvalue (frexp), 0

[isakhilesh]

Hello,
Can this issue be assigned to me, I want to work on this?
Thanks

[akielaries]

@isakhilesh are you still working on this?

[isakhilesh]

@isakhilesh are you still working on this?

Hey, yes I am working on the issue.

[Verylostpenguin]

Hi @isakhilesh, are you still working on this? What progress have you made?

[Verylostpenguin]

As @isakhilesh doesn't seem to be working on the issue anymore, can I be assigned the issue instead?

[vortex73]

Hey this looks intriguing! Unless someone is still working on it could it be assigned to me?