Mesa (staging/21.2): glsl: Properly handle .length() of an unsized array

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Module: Mesa
Branch: staging/21.2
Commit: 319818e9fdd8adb81d87d838cecbb343a272a34f
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=319818e9fdd8adb81d87d838cecbb343a272a34f

Author: Yevhenii Kolesnikov <yevhenii.kolesnikov at globallogic.com>
Date:   Wed Jul 14 20:52:56 2021 +0300

glsl: Properly handle .length() of an unsized array

There are two distinct cases:
- The last member of a shader storage block (length determined at run-time)
- Implicitly-sized array (length determined at link-time)

Fixes: 273f61a0051a ("glsl: Add parser/compiler support for unsized array's length()")
Signed-off-by: Yevhenii Kolesnikov <yevhenii.kolesnikov at globallogic.com>
Reviewed-by: Timothy Arceri <tarceri at itsqueeze.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11952>
(cherry picked from commit c3f47f6e300ef1ec18b2c55ec82bccf263292351)

---

 .pick_status.json                  |  2 +-
 src/compiler/glsl/ast_function.cpp | 14 +++++++++++---
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/.pick_status.json b/.pick_status.json
index 9e087012cce..5c44ab19916 100644
--- a/.pick_status.json
+++ b/.pick_status.json
@@ -94,7 +94,7 @@
         "description": "glsl: Properly handle .length() of an unsized array",
         "nominated": true,
         "nomination_type": 1,
-        "resolution": 0,
+        "resolution": 1,
         "main_sha": null,
         "because_sha": "273f61a0051a794d1a39d70fb1dbf46a3ca3c63f"
     },
diff --git a/src/compiler/glsl/ast_function.cpp b/src/compiler/glsl/ast_function.cpp
index 73e72b5baa9..92ca6a4cf1b 100644
--- a/src/compiler/glsl/ast_function.cpp
+++ b/src/compiler/glsl/ast_function.cpp
@@ -2047,10 +2047,18 @@ ast_function_expression::handle_method(exec_list *instructions,
                                 "length called on unsized array"
                                 " only available with"
                                 " ARB_shader_storage_buffer_object");
+               goto fail;
+            } else if (op->variable_referenced()->is_in_shader_storage_block()) {
+               /* Calculate length of an unsized array in run-time */
+               result = new(ctx)
+                  ir_expression(ir_unop_ssbo_unsized_array_length, op);
+            } else {
+               /* When actual size is known at link-time, this will be
+                * replaced with a constant expression.
+                */
+               result = new (ctx)
+                  ir_expression(ir_unop_implicitly_sized_array_length, op);
             }
-            /* Calculate length of an unsized array in run-time */
-            result = new(ctx) ir_expression(ir_unop_ssbo_unsized_array_length,
-                                            op);
          } else {
             result = new(ctx) ir_constant(op->type->array_size());
          }