llvmpipe,draw,gallivm: Ensure we don't walk beyond the end of the shader variant list.

u_simple_list.h uses a sentinel element, and not a NULL element. So
ensure list is not empty when reducing the list of shader variants.

Something I noticed while trying to free variants more aggressively.

Reviewed-by: Brian Paul <[email protected]>

2 files changed, 11 insertions, 3 deletions

diff --git a/src/gallium/drivers/llvmpipe/lp_state_fs.c b/src/gallium/drivers/llvmpipe/lp_state_fs.c
index 90f9271223c..26f8d7ff765 100644
--- a/src/gallium/drivers/llvmpipe/lp_state_fs.c
+++ b/src/gallium/drivers/llvmpipe/lp_state_fs.c
@@ -1373,10 +1373,12 @@ llvmpipe_update_fs(struct llvmpipe_context *lp)
          if (lp->nr_fs_variants >= LP_MAX_SHADER_VARIANTS) {
             for (i = 0; i < LP_MAX_SHADER_VARIANTS / 4; i++) {
                struct lp_fs_variant_list_item *item;
-               item = last_elem(&lp->fs_variants_list);
-               if (!item) {
+               if (is_empty_list(&lp->fs_variants_list)) {
                   break;
                }
+               item = last_elem(&lp->fs_variants_list);
+               assert(item);
+               assert(item->base);
                llvmpipe_remove_shader_variant(lp, item->base);
             }
          }
diff --git a/src/gallium/drivers/llvmpipe/lp_state_setup.c b/src/gallium/drivers/llvmpipe/lp_state_setup.c
index 97c9238f989..3243abff6e0 100644
--- a/src/gallium/drivers/llvmpipe/lp_state_setup.c
+++ b/src/gallium/drivers/llvmpipe/lp_state_setup.c
@@ -837,7 +837,13 @@ cull_setup_variants(struct llvmpipe_context *lp)
    llvmpipe_finish(pipe, __FUNCTION__);
 
    for (i = 0; i < LP_MAX_SETUP_VARIANTS / 4; i++) {
-      struct lp_setup_variant_list_item *item = last_elem(&lp->setup_variants_list);
+      struct lp_setup_variant_list_item *item;
+      if (is_empty_list(&lp->setup_variants_list)) {
+         break;
+      }
+      item = last_elem(&lp->setup_variants_list);
+      assert(item);
+      assert(item->base);
       remove_setup_variant(lp, item->base);
    }
 }