Mesa (18.3): st/glsl_to_nir: fix incorrect arrary access

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Module: Mesa
Branch: 18.3
Commit: d29dca6d1589336cd33e6fbfec01e765859036f1
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=d29dca6d1589336cd33e6fbfec01e765859036f1

Author: Timothy Arceri <tarceri at itsqueeze.com>
Date:   Fri Mar  1 21:35:41 2019 +1100

st/glsl_to_nir: fix incorrect arrary access

This fixes a segfault when we try to access the array using a
-1 when the array wasn't allocated in the first place.

Before 7536af670b75 we would just access a pre-allocated array
that was also load/stored to/from the shader cache. But now the
cache will no longer allocate these arrays if they are empty.
The change resulted in tests such as the following segfaulting
when run with a warm shader cache.

tests/spec/arb_arrays_of_arrays/execution/sampler/fs-struct-const-index.shader_test

(cherry picked from commit cb2898f4786f9e80e0a2dd061d620fc7ced6f1ea)

---

 src/mesa/state_tracker/st_glsl_to_nir.cpp | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/mesa/state_tracker/st_glsl_to_nir.cpp b/src/mesa/state_tracker/st_glsl_to_nir.cpp
index 581a8639ef0..37388471423 100644
--- a/src/mesa/state_tracker/st_glsl_to_nir.cpp
+++ b/src/mesa/state_tracker/st_glsl_to_nir.cpp
@@ -290,13 +290,16 @@ st_nir_assign_uniform_locations(struct gl_context *ctx,
       } else {
          loc = st_nir_lookup_parameter_index(prog->Parameters, uniform->name);
 
-         if (ctx->Const.PackedDriverUniformStorage) {
+         /* We need to check that loc is not -1 here before accessing the
+          * array. It can be negative for example when we have a struct that
+          * only contains opaque types.
+          */
+         if (loc >= 0 && ctx->Const.PackedDriverUniformStorage) {
             loc = prog->Parameters->ParameterValueOffset[loc];
          }
       }
 
       uniform->data.driver_location = loc;
-
       max = MAX2(max, loc + type_size(uniform->type));
    }
    *size = max;