[PATCH] D142749: AMDGPU: Push fneg into bitcast of integer select

[David Stuttard via Phabricator via llvm-commits]

dstuttard added a comment.

This commit is causing some regression for us in some games.

Here's a reproducer (you get a cannot yet select error):

  target datalayout = "e-p:64:64-p1:64:64-p2:32:32-p3:32:32-p4:64:64-p5:32:32-p6:32:32-i64:64-v16:16-v24:32-v32:32-v48:64-v96:128-v192:256-v256:256-v512:512-v1024:1024-v2048:2048-n32:64-S
  32-A5-G1-ni:7"
  target triple = "amdgcn--amdpal"
  
  define amdgpu_cs void @_amdgpu_cs_main(float %.i2369) {
  .entry:
    %0 = fcmp uge float %.i2369, 0.000000e+00
    %.i2379 = select i1 %0, i32 1, i32 0
    %.i0436 = bitcast i32 %.i2379 to float
    %.i0440 = fneg float %.i0436
    %1 = fcmp uge float %.i0436, 0.000000e+00
    %.i2495 = select i1 %1, i32 %.i2379, i32 0
    %.i0552 = bitcast i32 %.i2495 to float
    %.i0592 = fmul float %.i0440, %.i0552
    %.i0721 = fcmp ogt float %.i0592, 0.000000e+00
    br i1 %.i0721, label %6, label %2
  
  2:                                                ; preds = %.entry
    %3 = call <2 x i32> @llvm.amdgcn.s.buffer.load.v2i32(<4 x i32> zeroinitializer, i32 1, i32 0)
    %4 = shufflevector <2 x i32> %3, <2 x i32> zeroinitializer, <4 x i32> <i32 0, i32 1, i32 undef, i32 undef>
    %5 = bitcast <4 x i32> %4 to <4 x float>
    %.i0753 = extractelement <4 x float> %5, i64 0
    br label %6
  
  6:                                                ; preds = %2, %.entry
    ret void
  }
  
  ; Function Attrs: nocallback nofree nosync nounwind willreturn memory(none)
  declare <2 x i32> @llvm.amdgcn.s.buffer.load.v2i32(<4 x i32>, i32, i32 immarg) #0
  
  attributes #0 = { nocallback nofree nosync nounwind willreturn memory(none) }

It looks to me that the part that does a "ReplaceAllUsesWith" is causing the problem since it replaces a select returning an i32 with one returning a float, which in this case causes failure in the subsequent bitcast. (See %.i0436 bitcast)


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D142749/new/

https://reviews.llvm.org/D142749