Instead of testing each bit when iterating a bitmask, we can use ffsl
to skip over unset bits in single instruction. That way it will scale
by the number of bits set, not the total number of bits.
ffsl is a non-standard function which glibc only provides by defining
GNUC_SOURCE. However if we are compiling with GCC we can avoid that
mess and just use the equivalent builtin. When not compiling for GCC
it will fall back to _cogl_util_ffs if the size of ints and longs are
the same (which is the case on i686). Otherwise it fallbacks to a slow
function implementation.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
Instead of storing only 31 bits in the pointer for a CoglBitmask, it
now assumes it can store a whole unsigned long minus the one bit used
to mark whether it has been converted to a GArray or not. This works
on the assumption that we can cast an unsigned long to a pointer and
back without losing information which I think should be true for any
platforms that Cogl is interested in. This has the advantage that on
64-bit architectures we can store 63 bits before we have to resort to
using a GArray at no extra cost. The values in the GArray are now
stored as unsigned longs as well on the assumption that it is more
efficient to load and store data in chunks of longs rather than ints.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
When the GLES2 wrapper is removed we can't use the fixed function API
such as glColorPointer to set the builtin attributes. Instead the GLSL
progend now maintains a cache of attribute locations that are queried
with glGetAttribLocation. The code that previously maintained a cache
of the enabled texture coord arrays has been modified to also cache
the enabled vertex attributes under GLES2. The vertex attribute API is
now the only place that is using this cache so it has been moved into
cogl-vertex-attribute.c
This implements a growable array of bits called CoglBitmask. The
CoglBitmask is intended to be cheap if less than 32 bits are used. If
more bits are required it will allocate a GArray. The type is meant to
be allocated on the stack but because it can require additional
resources it also has a destroy function.
http://bugzilla.openedhand.com/show_bug.cgi?id=2132
