[SPIRV] Share a test between DXIL & SPIRV backends

[Keenuts]

Summary

The SPIR-V backend is not ready yet to compile graphic shaders. So we
have no test that could pass with both backends except this one.

But in the future, we'd have 2 backends available for the HLSL
frontend: DXIL and SPIRV.
In DirectXShaderCompiler, a common source of bugs was uneven coverage
of features between both backends.
The goal here is to determine the canonical way to share tests.

The main issue is around XFAIL: in an ideal world, we could link
each XFAIL to a RUN line, but right now it's not possible.
This means we cannot mark the test as XFAIL just for 1 backend.

[Keenuts]

Hello!
For now this only changes a test in the SPIR-V backend, but the idea would be to do the same on the DXIL backend as we bring support 😊

All the best,

[Keenuts]

Abandoning this one. We'll probably end-up doing a test/HLSL folder to share common tests with the DXIL backend.

llvm/test/CodeGen/SPIRV/empty-module.ll

-; RUN: llc -O0 -mtriple=spirv64-unknown-unknown %s -o - | FileCheck %s
+; RUN: %if spirv-registered-target %{ llc -O0 -mtriple=spirv64-unknown-unknown %s -o - | FileCheck %s --check-prefix=SPIRV-CHECK %}
+; RUN: %if directx-registered-target %{ llc -O0 -mtriple=dxil-pc-shadermodel6.0-library %s -o - | FileCheck %s --check-prefix=DXIL-CHECK %}
 
-; CHECK-DAG: OpCapability Addresses
-; CHECK-DAG: OpCapability Linkage
-; CHECK-DAG: OpCapability Kernel
-; CHECK:     %1 = OpExtInstImport "OpenCL.std"
-; CHECK:     OpMemoryModel Physical64 OpenCL
-; CHECK:     OpSource Unknown 0
+; SPIRV-CHECK-DAG: OpCapability Addresses
+; SPIRV-CHECK-DAG: OpCapability Linkage
+; SPIRV-CHECK-DAG: OpCapability Kernel
+; SPIRV-CHECK:     %1 = OpExtInstImport "OpenCL.std"
+; SPIRV-CHECK:     OpMemoryModel Physical64 OpenCL
+; SPIRV-CHECK:     OpSource Unknown 0
+
+; DXIL-CHECK: target datalayout = "e-m:e-p:32:32-i1:32-i8:8-i16:16-i32:32-i64:64-f16:16-f32:32-f64:64-n8:16:32:64"
+; DXIL-CHECK: target triple = "dxil-pc-shadermodel6.0-library"