[HLSL][SPIRV] Add error test for unpackhalf2x16 (#166969)

Add an error test to check that a suitable error diagnostic is generated
for the use of the GL::unpackhalf2x16 operation in
 invalid contexts.

Fixes #166965

Co-authored-by: Tim Corringham <[email protected]>

Author: tcorringham

llvm/test/CodeGen/SPIRV/opencl/unpackhalf2x16-error.ll

@@ -0,0 +1,11 @@
+; RUN: not llc -verify-machineinstrs -O0 -mtriple=spirv64-unknown-unknown %s -o /dev/null 2>&1 | FileCheck %s
+; RUN: not llc -verify-machineinstrs -O0 -mtriple=spirv32-unknown-unknown %s -o /dev/null 2>&1 | FileCheck %s
+
+; CHECK: LLVM ERROR: %5:vfid(<2 x s64>) = nnan ninf nsz arcp afn reassoc G_INTRINSIC intrinsic(@llvm.spv.unpackhalf2x16), %0:iid(s64) is only supported with the GLSL extended instruction set.
+
+define hidden spir_func noundef nofpclass(nan inf) float @_Z9test_funcj(i32 noundef %0) local_unnamed_addr #0 {
+  %2 = tail call reassoc nnan ninf nsz arcp afn <2 x float> @llvm.spv.unpackhalf2x16.v2f32(i32 %0)
+  %3 = extractelement <2 x float> %2, i64 0
+  ret float %3
+}
+