intel/fs: Exclude control sources from execution type and region alignment calculations.

Currently the execution type calculation will return a bogus value in
cases like:

  mov_indirect(8) vgrf0:w, vgrf1:w, vgrf2:ud, 32u

Which will be considered to have a 32-bit integer execution type even
though the actual indirect move operation will be carried out with
16-bit precision.

Similarly there's no need to apply the CHV/BXT double-precision region
alignment restrictions to such control sources, since they aren't
directly involved in the double-precision arithmetic operations
emitted by these virtual instructions.  Applying the CHV/BXT
restrictions to control sources was expected to be harmless if mildly
inefficient, but unfortunately it exposed problems at codegen level
for virtual instructions (namely the SHUFFLE instruction used for the
Vulkan 1.1 subgroup feature) that weren't prepared to accept control
sources with an arbitrary strided region.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=109328
Reported-by: Mark Janes <mark.a.janes@intel.com>
Fixes: efa4e4bc5f "intel/fs: Introduce regioning lowering pass."
Tested-by: Anuj Phogat <anuj.phogat@gmail.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>

src/intel/compiler/brw_ir_fs.h

@@ -357,6 +357,13 @@ public:
    bool can_change_types() const;
    bool has_source_and_destination_hazard() const;
 
+   /**
+    * Return whether \p arg is a control source of a virtual instruction which
+    * shouldn't contribute to the execution type and usual regioning
+    * restriction calculations of arithmetic instructions.
+    */
+   bool is_control_source(unsigned arg) const;
+
    /**
     * Return the subset of flag registers read by the instruction as a bitset
     * with byte granularity.
@@ -461,7 +468,8 @@ get_exec_type(const fs_inst *inst)
    brw_reg_type exec_type = BRW_REGISTER_TYPE_B;
 
    for (int i = 0; i < inst->sources; i++) {
-      if (inst->src[i].file != BAD_FILE) {
+      if (inst->src[i].file != BAD_FILE &&
+          !inst->is_control_source(i)) {
          const brw_reg_type t = get_exec_type(inst->src[i].type);
          if (type_sz(t) > type_sz(exec_type))
             exec_type = t;