[Mesa-dev] [PATCH 5/5] glsl/linker: Safely generate mask of possible locations

[Ian Romanick]

From: Ian Romanick <ian.d.romanick at intel.com>

If MaxAttribs were ever raised to 32, undefined behavior would occur.
We had already gone to the effort (albeit incorrectly) handle this in
one case, so fix them all.

CID: 1369628
Signed-off-by: Ian Romanick <ian.d.romanick at intel.com>
---
 src/compiler/glsl/linker.cpp | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/compiler/glsl/linker.cpp b/src/compiler/glsl/linker.cpp
index 010f591..04c8692 100644
--- a/src/compiler/glsl/linker.cpp
+++ b/src/compiler/glsl/linker.cpp
@@ -2564,6 +2564,8 @@ find_available_slots(unsigned used_mask, unsigned needed_count)
 }
 
 
+#define SAFE_MASK_FROM_INDEX(i) (((i) >= 32) ? ~0 : ((1 << (i)) - 1))
+
 /**
  * Assign locations for either VS inputs or FS outputs
  *
@@ -2594,8 +2596,7 @@ assign_attribute_or_color_locations(void *mem_ctx,
 
    /* Mark invalid locations as being used.
     */
-   unsigned used_locations = (max_index >= 32)
-      ? 0 : ~((1 << max_index) - 1);
+   unsigned used_locations = ~SAFE_MASK_FROM_INDEX(max_index);
    unsigned double_storage_locations = 0;
 
    assert((target_index == MESA_SHADER_VERTEX)
@@ -2948,7 +2949,7 @@ assign_attribute_or_color_locations(void *mem_ctx,
 
    if (target_index == MESA_SHADER_VERTEX) {
       unsigned total_attribs_size =
-         _mesa_bitcount(used_locations & ((1 << max_index) - 1)) +
+         _mesa_bitcount(used_locations & SAFE_MASK_FROM_INDEX(max_index)) +
          _mesa_bitcount(double_storage_locations);
       if (total_attribs_size > max_index) {
          linker_error(prog,
@@ -3012,7 +3013,7 @@ assign_attribute_or_color_locations(void *mem_ctx,
     */
    if (target_index == MESA_SHADER_VERTEX) {
       unsigned total_attribs_size =
-         _mesa_bitcount(used_locations & ((1 << max_index) - 1)) +
+         _mesa_bitcount(used_locations & SAFE_MASK_FROM_INDEX(max_index)) +
          _mesa_bitcount(double_storage_locations);
       if (total_attribs_size > max_index) {
          linker_error(prog,
-- 
2.9.5