Mesa (staging/22.0): nir: Handle out of bounds access in nir_vectorize_tess_levels.

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Module: Mesa
Branch: staging/22.0
Commit: 4ebb55c3971d737fc6a75b02a9c4b0195f699f6e
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=4ebb55c3971d737fc6a75b02a9c4b0195f699f6e

Author: Timur Kristóf <timur.kristof at gmail.com>
Date:   Wed Apr  6 18:53:20 2022 +0200

nir: Handle out of bounds access in nir_vectorize_tess_levels.

Replace out of bounds loads with undef.
Then, delete instructions with out of bounds access.

Fixes: f5adf27fb926a330a13af716f0a03da1a224656d "nir,radv: add and use nir_vectorize_tess_levels()"
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/6264
Signed-off-by: Timur Kristóf <timur.kristof at gmail.com>
Reviewed-by: Rhys Perry <pendingchaos02 at gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15775>
(cherry picked from commit a7147ef1e86af5dbc39371885664f05030b3b418)

---

 .pick_status.json                         |  2 +-
 src/compiler/nir/nir_lower_io_to_vector.c | 23 ++++++++++++++++++++---
 2 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/.pick_status.json b/.pick_status.json
index 67fc7087e23..e3168311fcf 100644
--- a/.pick_status.json
+++ b/.pick_status.json
@@ -108,7 +108,7 @@
         "description": "nir: Handle out of bounds access in nir_vectorize_tess_levels.",
         "nominated": true,
         "nomination_type": 1,
-        "resolution": 0,
+        "resolution": 1,
         "because_sha": "f5adf27fb926a330a13af716f0a03da1a224656d"
     },
     {
diff --git a/src/compiler/nir/nir_lower_io_to_vector.c b/src/compiler/nir/nir_lower_io_to_vector.c
index c2224f8f409..9878f180adb 100644
--- a/src/compiler/nir/nir_lower_io_to_vector.c
+++ b/src/compiler/nir/nir_lower_io_to_vector.c
@@ -613,7 +613,7 @@ nir_vectorize_tess_levels_impl(nir_function_impl *impl)
    nir_builder_init(&b, impl);
 
    nir_foreach_block(block, impl) {
-      nir_foreach_instr(instr, block) {
+      nir_foreach_instr_safe(instr, block) {
          if (instr->type != nir_instr_type_intrinsic)
             continue;
 
@@ -633,7 +633,8 @@ nir_vectorize_tess_levels_impl(nir_function_impl *impl)
 
          assert(deref->deref_type == nir_deref_type_array);
          assert(nir_src_is_const(deref->arr.index));
-         unsigned index = nir_src_as_uint(deref->arr.index);;
+         unsigned index = nir_src_as_uint(deref->arr.index);
+         unsigned vec_size = glsl_get_vector_elements(var->type);
 
          b.cursor = nir_before_instr(instr);
          nir_ssa_def *new_deref = &nir_build_deref_var(&b, var)->dest.ssa;
@@ -641,7 +642,23 @@ nir_vectorize_tess_levels_impl(nir_function_impl *impl)
 
          nir_deref_instr_remove_if_unused(deref);
 
-         intrin->num_components = glsl_get_vector_elements(var->type);
+         intrin->num_components = vec_size;
+
+         /* Handle out of bounds access. */
+         if (index >= vec_size) {
+            if (intrin->intrinsic == nir_intrinsic_load_deref) {
+               /* Return undef from out of bounds loads. */
+               b.cursor = nir_after_instr(instr);
+               nir_ssa_def *val = &intrin->dest.ssa;
+               nir_ssa_def *u = nir_ssa_undef(&b, val->num_components, val->bit_size);
+               nir_ssa_def_rewrite_uses(val, u);
+            }
+
+            /* Finally, remove the out of bounds access. */
+            nir_instr_remove(instr);
+            progress = true;
+            continue;
+         }
 
          if (intrin->intrinsic == nir_intrinsic_store_deref) {
             nir_intrinsic_set_write_mask(intrin, 1 << index);