[AMDGPU] Add test case for zext of f16 to i32

Preserve the test case from this abandoned review:
D51925 [AMDGPU] Fix issue for zext of f16 to i32

llvm/test/CodeGen/AMDGPU/mad-mix-lo.ll

@@ -2202,6 +2202,56 @@ define <4 x half> @v_mad_mix_v4f32_clamp_precvt(<4 x half> %src0, <4 x half> %sr
   ret <4 x half> %cvt.result
 }
 
+define i32 @mixlo_zext(float %src0, float %src1, float %src2) #0 {
+; GFX1100-LABEL: mixlo_zext:
+; GFX1100:       ; %bb.0:
+; GFX1100-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
+; GFX1100-NEXT:    v_fma_mixlo_f16 v0, v0, v1, v2
+; GFX1100-NEXT:    s_delay_alu instid0(VALU_DEP_1)
+; GFX1100-NEXT:    v_and_b32_e32 v0, 0xffff, v0
+; GFX1100-NEXT:    s_setpc_b64 s[30:31]
+;
+; GFX900-LABEL: mixlo_zext:
+; GFX900:       ; %bb.0:
+; GFX900-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
+; GFX900-NEXT:    v_mad_mixlo_f16 v0, v0, v1, v2
+; GFX900-NEXT:    v_and_b32_e32 v0, 0xffff, v0
+; GFX900-NEXT:    s_setpc_b64 s[30:31]
+;
+; GFX906-LABEL: mixlo_zext:
+; GFX906:       ; %bb.0:
+; GFX906-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
+; GFX906-NEXT:    v_fma_mixlo_f16 v0, v0, v1, v2
+; GFX906-NEXT:    v_and_b32_e32 v0, 0xffff, v0
+; GFX906-NEXT:    s_setpc_b64 s[30:31]
+;
+; VI-LABEL: mixlo_zext:
+; VI:       ; %bb.0:
+; VI-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
+; VI-NEXT:    v_mac_f32_e32 v2, v0, v1
+; VI-NEXT:    v_cvt_f16_f32_e32 v0, v2
+; VI-NEXT:    s_setpc_b64 s[30:31]
+;
+; SDAG-CI-LABEL: mixlo_zext:
+; SDAG-CI:       ; %bb.0:
+; SDAG-CI-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
+; SDAG-CI-NEXT:    v_mac_f32_e32 v2, v0, v1
+; SDAG-CI-NEXT:    v_cvt_f16_f32_e32 v0, v2
+; SDAG-CI-NEXT:    s_setpc_b64 s[30:31]
+;
+; GISEL-CI-LABEL: mixlo_zext:
+; GISEL-CI:       ; %bb.0:
+; GISEL-CI-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
+; GISEL-CI-NEXT:    v_mac_f32_e32 v2, v0, v1
+; GISEL-CI-NEXT:    v_cvt_f16_f32_e32 v0, v2
+; GISEL-CI-NEXT:    s_setpc_b64 s[30:31]
+  %result = call float @llvm.fmuladd.f32(float %src0, float %src1, float %src2)
+  %cvt.result = fptrunc float %result to half
+  %cvt.result.i16 = bitcast half %cvt.result to i16
+  %cvt.result.i32 = zext i16 %cvt.result.i16 to i32
+  ret i32 %cvt.result.i32
+}
+
 define half @mixlo_fptrunc(float %a, float %b) #0 {
 ; GFX1100-LABEL: mixlo_fptrunc:
 ; GFX1100:       ; %bb.0: ; %.entry