intel/brw/validate: Simplify grf span validation check by not using a mask

Previously this check would create a mask of the bytes used in the
grf, and then shift the mask. This worked well when there was 32 bytes
in the register because a 64-bit uint64_t could easily detect that
bytes were used in the next regiter. (The next register was the high
32-bits of the `access_mask` variable.)

With Xe2, the register size becomes 64 bytes, meaning this strategy
doesn't work. Instead of a mask, we can just check to see if more than
1 grfs are used during each loop iteration. (Suggested by Ken.) This
will make it easier to extend for Xe2 in a follow on commit.

Verified this with
dEQP-VK.subgroups.arithmetic.compute.subgroupexclusivemul_u64vec4_requiredsubgroupsize
on Xe2, which otherwise would cause the program to fail to validate
because it assumed a grf was 32 bytes.

Backport-to: 24.2
Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28479>
(cherry picked from commit f2800deacbf1d8d55b18f8fe1ec01930328c220c)

1 files changed, 8 insertions, 4 deletions

diff --git a/src/intel/compiler/brw_eu_validate.c b/src/intel/compiler/brw_eu_validate.c
index 3b6ed6a1518..6ba117e7f87 100644
--- a/src/intel/compiler/brw_eu_validate.c
+++ b/src/intel/compiler/brw_eu_validate.c
@@ -1075,21 +1075,25 @@ general_restrictions_on_region_parameters(const struct brw_isa_info *isa,
       /* VertStride must be used to cross GRF register boundaries. This rule
        * implies that elements within a 'Width' cannot cross GRF boundaries.
        */
-      const uint64_t mask = (1ULL << element_size) - 1;
       unsigned rowbase = subreg;
 
       for (int y = 0; y < exec_size / width; y++) {
-         uint64_t access_mask = 0;
+         bool spans_grfs = false;
          unsigned offset = rowbase;
+         unsigned first_grf = offset / REG_SIZE;
 
          for (int x = 0; x < width; x++) {
-            access_mask |= mask << (offset % 64);
+            const unsigned end_byte = offset + (element_size - 1);
+            const unsigned end_grf = end_byte / REG_SIZE;
+            spans_grfs = end_grf != first_grf;
+            if (spans_grfs)
+               break;
             offset += hstride * element_size;
          }
 
          rowbase += vstride * element_size;
 
-         if ((uint32_t)access_mask != 0 && (access_mask >> 32) != 0) {
+         if (spans_grfs) {
             ERROR("VertStride must be used to cross GRF register boundaries");
             break;
          }