nir_lower_mem_access_bit_sizes: fix negative chunk offsets

With a 64 bit pointer model, instead of doing -1 the pass ended up doing
+4294967295. The reason here was some implicit integer conversion going
horribly wrong, so just do the offset math in 64 bit to get a nice result.

Cc: mesa-stable
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/13023
Reviewed-by: Faith Ekstrand <faith.ekstrand@collabora.com>
Reviewed-by: Rhys Perry <pendingchaos02@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/34669>
(cherry picked from commit 33965bb21bac40840cf07958f509dcada4ead979)

.pick_status.json

@@ -774,7 +774,7 @@
         "description": "nir_lower_mem_access_bit_sizes: fix negative chunk offsets",
         "nominated": true,
         "nomination_type": 1,
-        "resolution": 0,
+        "resolution": 1,
         "main_sha": null,
         "because_sha": null,
         "notes": null

src/compiler/nir/nir_lower_mem_access_bit_sizes.c

@@ -239,7 +239,7 @@ lower_mem_load(nir_builder *b, nir_intrinsic_instr *intrin,
          /* In this case, we know how much to adjust the offset */
          uint32_t delta = chunk_align_offset % requested.align;
          nir_def *load_offset =
-            nir_iadd_imm(b, offset, chunk_start - (int)delta);
+            nir_iadd_imm(b, offset, (int64_t)chunk_start - (int64_t)delta);
 
          const uint32_t load_align_offset =
             (chunk_align_offset - delta) % align_mul;