[x86] LLVM ERROR: Cannot select: t28: v8i32 = X86ISD::CVTTP2UI t27

[nikic]

; RUN: llc -mattr=+avx512f < %s
define <16 x i32> @test() {
  %res = call <16 x i32> @llvm.x86.avx512.mask.cvttps2udq.512(<16 x float> zeroinitializer, <16 x i32> zeroinitializer, i16 255, i32 4)
  ret <16 x i32> %res
}

Results in:

LLVM ERROR: Cannot select: t28: v8i32 = X86ISD::CVTTP2UI t27
  t27: v8f32 = BUILD_VECTOR ConstantFP:f32<0.000000e+00>, ConstantFP:f32<0.000000e+00>, ConstantFP:f32<0.000000e+00>, ConstantFP:f32<0.000000e+00>, ConstantFP:f32<0.000000e+00>, ConstantFP:f32<0.000000e+00>, ConstantFP:f32<0.000000e+00>, ConstantFP:f32<0.000000e+00>

Note that CVTTP2UI originally had v16i32 result and was narrowed to v8i32, so it now requires +avx512vl as well, leading to a selection failure.

[llvmbot]

@llvm/issue-subscribers-backend-x86

Author: Nikita Popov (nikic)

Details

```llvm ; RUN: llc -mattr=+avx512f < %s define <16 x i32> @test() { %res = call <16 x i32> @llvm.x86.avx512.mask.cvttps2udq.512(<16 x float> zeroinitializer, <16 x i32> zeroinitializer, i16 255, i32 4) ret <16 x i32> %res } ``` Results in: ``` LLVM ERROR: Cannot select: t28: v8i32 = X86ISD::CVTTP2UI t27 t27: v8f32 = BUILD_VECTOR ConstantFP:f32<0.000000e+00>, ConstantFP:f32<0.000000e+00>, ConstantFP:f32<0.000000e+00>, ConstantFP:f32<0.000000e+00>, ConstantFP:f32<0.000000e+00>, ConstantFP:f32<0.000000e+00>, ConstantFP:f32<0.000000e+00>, ConstantFP:f32<0.000000e+00> ```

Note that CVTTP2UI originally had v16i32 result and was narrowed to v8i32, so it now requires +avx512vl as well, leading to a selection failure.