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

[Farzon Lotfi via llvm-commits]

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@@ -506,22 +509,193 @@ static bool isConstReg(MachineRegisterInfo *MRI, Register OpReg) {
   return false;
 }
 
+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;
+  }
+}
+
+static bool isOpcodeWithNoSideEffects(unsigned Opcode) {
+  // TODO: This list should be generated by TableGen.
+  // Try to replace this with an opcode flag of some type to
+  // make sure that people are thinking about this when they add new opcodes.
----------------
farzonl wrote:

Can you file an issue for this?

Also if you add a todo with an issue like this to `intrinsicHasSideEffects` I'll consider that resolving my issue with that function.

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