broadcom/compiler: allow instruction merges in v71

In v3d 4.x there were restrictions based on the number of raddrs used
by the combined instructions, but we don't have these restrictions in
v3d 7.x.

It should be noted that while there are no restrictions on the number
of raddrs addressed, a QPU instruction can only address a single small
immediate, so we should be careful about that when we add support for
small immediates.

Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/25450>

src/broadcom/compiler/qpu_schedule.c

@@ -906,8 +906,11 @@ qpu_raddrs_used(const struct v3d_qpu_instr *a,
 static bool
 qpu_merge_raddrs(struct v3d_qpu_instr *result,
                  const struct v3d_qpu_instr *add_instr,
-                 const struct v3d_qpu_instr *mul_instr)
+                 const struct v3d_qpu_instr *mul_instr,
+                 const struct v3d_device_info *devinfo)
 {
+        assert(devinfo->ver <= 42);
+
         uint64_t raddrs_used = qpu_raddrs_used(add_instr, mul_instr);
         int naddrs = util_bitcount64(raddrs_used);
 
@@ -1111,9 +1114,19 @@ qpu_merge_inst(const struct v3d_device_info *devinfo,
                 add_instr = a;
         }
 
-        if (add_instr && mul_instr &&
-            !qpu_merge_raddrs(&merge, add_instr, mul_instr)) {
-                        return false;
+        /* V3D 4.x and earlier use muxes to select the inputs for the ALUs and
+         * they have restrictions on the number of raddrs that can be adressed
+         * in a single instruction.
+         *
+         * FIXME: for V3D 7.x we can't merge instructions if they address more
+         * than one small immediate. For now, we don't support small immediates,
+         * so it is not a problem.
+         */
+        if (devinfo->ver <= 42) {
+                if (add_instr && mul_instr &&
+                    !qpu_merge_raddrs(&merge, add_instr, mul_instr, devinfo)) {
+                                return false;
+                }
         }
 
         merge.sig.thrsw |= b->sig.thrsw;