[llvm] [SPIRV] Enable DCE in instruction selection and update tests (PR #168428)

[Nathan Gauër via llvm-commits]

================
@@ -506,22 +509,195 @@ static bool isConstReg(MachineRegisterInfo *MRI, Register OpReg) {
   return false;
 }
 
+// TODO(168736): We should make this either a flag in tabelgen
+// or reduce our dependence on the global registery, so we can remove this
+// function. It can easily be missed when new intrinsics are added.
+static bool intrinsicHasSideEffects(Intrinsic::ID ID) {
+  switch (ID) {
+  // Intrinsics that do not have side effects.
+  // This is not an exhaustive list and may need to be updated.
+  case Intrinsic::spv_all:
+  case Intrinsic::spv_alloca:
+  case Intrinsic::spv_any:
+  case Intrinsic::spv_bitcast:
+  case Intrinsic::spv_const_composite:
+  case Intrinsic::spv_cross:
+  case Intrinsic::spv_degrees:
+  case Intrinsic::spv_distance:
+  case Intrinsic::spv_extractelt:
+  case Intrinsic::spv_extractv:
+  case Intrinsic::spv_faceforward:
+  case Intrinsic::spv_fdot:
+  case Intrinsic::spv_firstbitlow:
+  case Intrinsic::spv_firstbitshigh:
+  case Intrinsic::spv_firstbituhigh:
+  case Intrinsic::spv_frac:
+  case Intrinsic::spv_gep:
+  case Intrinsic::spv_global_offset:
+  case Intrinsic::spv_global_size:
+  case Intrinsic::spv_group_id:
+  case Intrinsic::spv_insertelt:
+  case Intrinsic::spv_insertv:
+  case Intrinsic::spv_isinf:
+  case Intrinsic::spv_isnan:
+  case Intrinsic::spv_lerp:
+  case Intrinsic::spv_length:
+  case Intrinsic::spv_normalize:
+  case Intrinsic::spv_num_subgroups:
+  case Intrinsic::spv_num_workgroups:
+  case Intrinsic::spv_ptrcast:
+  case Intrinsic::spv_radians:
+  case Intrinsic::spv_reflect:
+  case Intrinsic::spv_refract:
+  case Intrinsic::spv_resource_getpointer:
+  case Intrinsic::spv_resource_handlefrombinding:
+  case Intrinsic::spv_resource_handlefromimplicitbinding:
+  case Intrinsic::spv_resource_nonuniformindex:
+  case Intrinsic::spv_rsqrt:
+  case Intrinsic::spv_saturate:
+  case Intrinsic::spv_sdot:
+  case Intrinsic::spv_sign:
+  case Intrinsic::spv_smoothstep:
+  case Intrinsic::spv_step:
+  case Intrinsic::spv_subgroup_id:
+  case Intrinsic::spv_subgroup_local_invocation_id:
+  case Intrinsic::spv_subgroup_max_size:
+  case Intrinsic::spv_subgroup_size:
+  case Intrinsic::spv_thread_id:
+  case Intrinsic::spv_thread_id_in_group:
+  case Intrinsic::spv_udot:
+  case Intrinsic::spv_undef:
+  case Intrinsic::spv_value_md:
+  case Intrinsic::spv_workgroup_size:
+    return false;
+  default:
+    return true;
+  }
+}
+
+// TODO(168736): We should make this either a flag in tabelgen
+// or reduce our dependence on the global registery, so we can remove this
----------------
Keenuts wrote:

```suggestion
// or reduce our dependence on the global registry, so we can remove this
```

https://github.com/llvm/llvm-project/pull/168428