[Mesa-dev] [PATCH 2/2] i965: initialize the alignment related bits in struct brw_reg

[Samuel Iglesias Gonsálvez]

With the inclusion of the "df" field in the union, this union is going
to be at the offset 8 because of the alignment rules. The alignment
bits in the middle are uninitialized and valgrind complains with errors
similar to this:

==10298== Conditional jump or move depends on uninitialised value(s)
==10298==    at 0x4C31D52: __memcmp_sse4_1 (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==10298==    by 0xAB16663: backend_reg::equals(backend_reg const&) const (brw_shader.cpp:690)
==10298==    by 0xAAB629D: fs_reg::equals(fs_reg&) const (brw_fs.cpp:456)
==10298==    by 0xAAD4452: operands_match(fs_inst*, fs_inst*, bool*) (brw_fs_cse.cpp:161)
==10298==    by 0xAAD46C3: instructions_match(fs_inst*, fs_inst*, bool*) (brw_fs_cse.cpp:187)
==10298==    by 0xAAD4BAA: fs_visitor::opt_cse_local(bblock_t*) (brw_fs_cse.cpp:251)
==10298==    by 0xAAD5216: fs_visitor::opt_cse() (brw_fs_cse.cpp:361)
==10298==    by 0xAAC8AAD: fs_visitor::optimize() (brw_fs.cpp:5401)
==10298==    by 0xAACB9DC: fs_visitor::run_fs(bool) (brw_fs.cpp:5803)
==10298==    by 0xAACC38B: brw_compile_fs (brw_fs.cpp:6029)
==10298==    by 0xAA39796: brw_codegen_wm_prog (brw_wm.c:137)
==10298==    by 0xAA3B068: brw_fs_precompile (brw_wm.c:637)

This patch adds an explicit padding and initializes it to zero.

Signed-off-by: Samuel Iglesias Gonsálvez <siglesias at igalia.com>
---

This patch replaces the following one:

[PATCH 2/2] i965: check each field separately in backend_end::equals()

 src/mesa/drivers/dri/i965/brw_reg.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/mesa/drivers/dri/i965/brw_reg.h b/src/mesa/drivers/dri/i965/brw_reg.h
index 3b76d7d..ebb7f29 100644
--- a/src/mesa/drivers/dri/i965/brw_reg.h
+++ b/src/mesa/drivers/dri/i965/brw_reg.h
@@ -243,6 +243,9 @@ struct brw_reg {
    unsigned subnr:5;              /* :1 in align16 */
    unsigned nr:16;
 
+   /* IMPORTANT: adjust padding bits if you add new fields */
+   unsigned padding:32;
+
    union {
       struct {
          unsigned swizzle:8;      /* src only, align16 only */
@@ -337,7 +340,7 @@ brw_reg(enum brw_reg_file file,
    reg.pad0 = 0;
    reg.subnr = subnr * type_sz(type);
    reg.nr = nr;
-
+   reg.padding = 0;
    /* Initialize all union's bits to zero before setting them. */
    reg.df = 0;
 
-- 
2.5.0