Mesa (master): glsl/linker: Safely generate mask of possible locations

[Ian Romanick]

Module: Mesa
Branch: master
Commit: 336afe7d7a8e066e1286bb93791d5c3d96ccc317
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=336afe7d7a8e066e1286bb93791d5c3d96ccc317

Author: Ian Romanick <ian.d.romanick at intel.com>
Date:   Fri Jan  5 18:43:32 2018 -0800

glsl/linker: Safely generate mask of possible locations

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>
Reviewed-by: Alejandro Piñeiro <apinheiro at igalia.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 d1f10eeecd..86ef5831b7 100644
--- a/src/compiler/glsl/linker.cpp
+++ b/src/compiler/glsl/linker.cpp
@@ -2552,6 +2552,8 @@ 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
  *
@@ -2582,8 +2584,7 @@ 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)
@@ -2936,7 +2937,7 @@ 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,
@@ -3000,7 +3001,7 @@ 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,