On 08/22/2013 02:59 AM, Liu Xin wrote:
Dear list,
i wonder if all vendors in mesa3d use intel's glsl compiler now? by
browsing glsl source code, i still don't understand how it generates
ir_texture. in my idea, it treats it as normal function call.
Yes, all drivers use the same shader compiler, in src/glsl.
for example, this is tiny fragment shader:
uniform sampler2D sampler2d;
varying mediump vec2 myTexCoord;
void main (void)
{
gl_FragColor = texture2D(sampler2d,myTexCoord);
}
glsl_compiler will emit LIR/HIR like this. please note (call texture2D
...). it's a normal ir_call instead of ir_texture. i confirm that
ast2hir doesn't new ir_texture in any case.
That's correct. At shader compile time, all built-in functions
(texturing, mix, abs, sin, etc.) are treated as normal functions.
We create several other shaders - stored in the builtins_to_link list -
and at link time, we link those with the user's shaders. Then, the
function inliner runs and replaces the (call ...) nodes.
If you run ./src/glsl/builtins/tools/texture_builtins.py, you can see
the IR for all of the texturing functions. The body of these functions
contain the (tex ...) nodes. ir_reader creates these, as part of
_mesa_glsl_initialize_functions().
The built-in code is kind of a mess...sorry for that.
(function main
(signature void
(parameters
)
(
(declare (temporary ) vec4 texture2D_retval@0x94fc11c)
(assign (constant bool (1)) (xyzw) (var_ref
texture2D_retval@0x94fc11c) (call texture2D ((var_ref
sampler2d@0x955b114) (var_ref myTexCoord@0x955b03c) ))
)
(assign (constant bool (1)) (xyzw) (var_ref
gl_FragColor@0x92c2eb4) (var_ref texture2D_retval@0x94fc11c) )
))
)
do mesa glsl compiler can make use of ir_texture? i think it must be yes
because all GPUs have texture unit and should handle tex commands. how
does mesa do it?
thanks,
--lx
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