Well...you need 7 bits/struct, so you can just use a byte array rather than
a struct array, and then manipulate each member using macros to hide the
ugly AND/OR/shifting. Would work for C89, for that matter.
On Wed, Sep 2, 2009 at 9:48 AM, Roland Scheidegger <[email protected]>wrote:
> Hmm, I'm not actually sure this will always reduce the state key size. I
> think the compiler is still allowed to pad the mode_opt struct out to
> whatever it likes (maybe #pragma pack(1) can prevent this), even though
> maybe gcc does not.
> I don't like pragmas too much, but it looks the only way to do this in
> some clean c99 way would be to get rid of the mode_opt struct entirely?
>
> Roland
>
> On 02.09.2009 16:23, Brian Paul wrote:
> > Unfortunately gcc (version 4.3.2 anyway) warns on this:
> > main/texenvprogram.c:87: warning: type of bit-field ‘Source’ is a GCC
> > extension
> > main/texenvprogram.c:88: warning: type of bit-field ‘Operand’ is a GCC
> > extension
> >
> > I'm trying to find a #pragma or something to silence the warning...
> >
> > -Brian
> >
> > Keith Whitwell wrote:
> >> Looks great Chris.
> >>
> >> Keith
> >>
> >> On Wed, 2009-09-02 at 05:11 -0700, Chris Wilson wrote:
> >>> By rearranging the bitfields within the key we can reduce the size
> >>> of the key from 644 to 196 bytes, reducing the cost of both the
> >>> hashing and equality tests.
> >>> ---
> >>> src/mesa/main/texenvprogram.c | 7 ++++---
> >>> 1 files changed, 4 insertions(+), 3 deletions(-)
> >>>
> >>> diff --git a/src/mesa/main/texenvprogram.c
> b/src/mesa/main/texenvprogram.c
> >>> index 5913957..3851937 100644
> >>> --- a/src/mesa/main/texenvprogram.c
> >>> +++ b/src/mesa/main/texenvprogram.c
> >>> @@ -82,8 +82,8 @@ texenv_doing_secondary_color(GLcontext *ctx)
> >>> #define DISASSEM (MESA_VERBOSE & VERBOSE_DISASSEM)
> >>>
> >>> struct mode_opt {
> >>> - GLuint Source:4; /**< SRC_x */
> >>> - GLuint Operand:3; /**< OPR_x */
> >>> + GLubyte Source:4; /**< SRC_x */
> >>> + GLubyte Operand:3; /**< OPR_x */
> >>> };
> >>>
> >>> struct state_key {
> >>> @@ -103,10 +103,11 @@ struct state_key {
> >>>
> >>> GLuint NumArgsRGB:3; /**< up to MAX_COMBINER_TERMS */
> >>> GLuint ModeRGB:5; /**< MODE_x */
> >>> - struct mode_opt OptRGB[MAX_COMBINER_TERMS];
> >>>
> >>> GLuint NumArgsA:3; /**< up to MAX_COMBINER_TERMS */
> >>> GLuint ModeA:5; /**< MODE_x */
> >>> +
> >>> + struct mode_opt OptRGB[MAX_COMBINER_TERMS];
> >>> struct mode_opt OptA[MAX_COMBINER_TERMS];
> >>> } unit[MAX_TEXTURE_UNITS];
> >>> };
> >>
> >>
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