test/CodeGen/AMDGPU/subreg-coalescer-undef-use.ll

; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
; RUN: llc -march=amdgcn -mcpu=tahiti -amdgpu-dce-in-ra=0 -o - %s | FileCheck %s
; Don't crash when the use of an undefined value is only detected by the
; register coalescer because it is hidden with subregister insert/extract.
target triple="amdgcn--"

define amdgpu_kernel void @foobar(float %a0, float %a1, float addrspace(1)* %out) nounwind {
; CHECK-LABEL: foobar:
; CHECK:       ; %bb.0: ; %entry
; CHECK-NEXT:    s_load_dwordx2 s[4:5], s[0:1], 0x9
; CHECK-NEXT:    s_load_dwordx2 s[0:1], s[0:1], 0xb
; CHECK-NEXT:    v_mbcnt_lo_u32_b32_e64 v0, -1, 0
; CHECK-NEXT:    v_cmp_eq_u32_e32 vcc, 0, v0
; CHECK-NEXT:    s_mov_b32 s2, -1
; CHECK-NEXT:    s_waitcnt lgkmcnt(0)
; CHECK-NEXT:    v_mov_b32_e32 v0, s4
; CHECK-NEXT:    v_mov_b32_e32 v1, s5
; CHECK-NEXT:    v_mov_b32_e32 v2, s6
; CHECK-NEXT:    v_mov_b32_e32 v3, s7
; CHECK-NEXT:    s_and_saveexec_b64 s[6:7], vcc
; CHECK-NEXT:  ; %bb.1: ; %ift
; CHECK-NEXT:    s_mov_b32 s4, s5
; CHECK-NEXT:    v_mov_b32_e32 v0, s4
; CHECK-NEXT:    v_mov_b32_e32 v1, s5
; CHECK-NEXT:    v_mov_b32_e32 v2, s6
; CHECK-NEXT:    v_mov_b32_e32 v3, s7
; CHECK-NEXT:  ; %bb.2: ; %ife
; CHECK-NEXT:    s_or_b64 exec, exec, s[6:7]
; CHECK-NEXT:    s_mov_b32 s3, 0xf000
; CHECK-NEXT:    buffer_store_dword v1, off, s[0:3], 0
; CHECK-NEXT:    s_endpgm

; FIXME: The change related to the fact that
; DetectDeadLanes pass hit "Copy across incompatible class" SGPR -> VGPR in analysis
; and hence it cannot derive the fact that the vector element in the "ift" block is unused.
; Such a copies appear because the float4 vectors and their elements in the test are uniform
; but the PHI node in "ife" block is divergent because of the CF dependency (divergent branch in bb0)
entry:
  %v0 = insertelement <4 x float> undef, float %a0, i32 0
  %tid = call i32 @llvm.amdgcn.mbcnt.lo(i32 -1, i32 0) #0
  %cnd = icmp eq i32 %tid, 0
  br i1 %cnd, label %ift, label %ife

ift:
  %v1 = insertelement <4 x float> undef, float %a1, i32 0
  br label %ife

ife:
  %val = phi <4 x float> [ %v1, %ift ], [ %v0, %entry ]
  %v2 = extractelement <4 x float> %val, i32 1
  store float %v2, float addrspace(1)* %out, align 4
  ret void
}

declare i32 @llvm.amdgcn.mbcnt.lo(i32, i32) #0

attributes #0 = { nounwind readnone }