[Mesa-dev] [PATCH 1/2] meta: Add a GLSL-based _mesa_meta_Clear() variant.

[Kenneth Graunke]

On 07/19/2011 01:46 PM, Ian Romanick wrote:
> On 07/18/2011 09:33 AM, Eric Anholt wrote:
>> This cuts out a large portion of the overhead of glClear() from
>> resetting the texenv state and recomputing the fixed function
>> programs.  It also means less use of fixed function internally in our
>> GLES2 drivers, which is rather bogus.
>> ---
>>  src/mesa/drivers/common/meta.c |  166 ++++++++++++++++++++++++++++++++++++++++
>>  src/mesa/drivers/common/meta.h |    3 +
>>  2 files changed, 169 insertions(+), 0 deletions(-)
> 
>> diff --git a/src/mesa/drivers/common/meta.c b/src/mesa/drivers/common/meta.c
>> index 0e58aec..09d7186 100644
>> --- a/src/mesa/drivers/common/meta.c
>> +++ b/src/mesa/drivers/common/meta.c
>> @@ -62,6 +62,7 @@
>>  #include "main/teximage.h"
>>  #include "main/texparam.h"
>>  #include "main/texstate.h"
>> +#include "main/uniforms.h"
>>  #include "main/varray.h"
>>  #include "main/viewport.h"
>>  #include "program/program.h"
>> @@ -235,6 +236,8 @@ struct clear_state
>>  {
>>     GLuint ArrayObj;
>>     GLuint VBO;
>> +   GLuint ShaderProg;
>> +   GLint ColorLocation;
>>  };
> 
> 
>> @@ -1589,6 +1592,169 @@ _mesa_meta_Clear(struct gl_context *ctx, GLbitfield buffers)
>>     _mesa_meta_end(ctx);
>>  }
> 
>> +static void
>> +meta_glsl_clear_init(struct gl_context *ctx, struct clear_state *clear)
>> +{
>> +   const char *vs_source =
>> +      "attribute vec4 position;\n"
>> +      "void main()\n"
>> +      "{\n"
>> +      "   gl_Position = position;\n"
>> +      "}\n";
>> +   const char *fs_source =
>> +      "uniform vec4 color;\n"
>> +      "void main()\n"
>> +      "{\n"
>> +      "   gl_FragColor = color;\n"
>> +      "}\n";
>> +   GLuint vs, fs;
>> +
>> +   if (clear->ArrayObj != 0)
>> +      return;
>> +
>> +   /* create vertex array object */
>> +   _mesa_GenVertexArrays(1, &clear->ArrayObj);
>> +   _mesa_BindVertexArray(clear->ArrayObj);
>> +
>> +   /* create vertex array buffer */
>> +   _mesa_GenBuffersARB(1, &clear->VBO);
>> +   _mesa_BindBufferARB(GL_ARRAY_BUFFER_ARB, clear->VBO);
>> +
>> +   /* setup vertex arrays */
>> +   _mesa_VertexAttribPointerARB(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float),
>> +				(void *)0);
>> +   _mesa_EnableVertexAttribArrayARB(0);
>> +
>> +   vs = _mesa_CreateShaderObjectARB(GL_VERTEX_SHADER);
>> +   _mesa_ShaderSourceARB(vs, 1, &vs_source, NULL);
>> +   _mesa_CompileShaderARB(vs);
>> +
>> +   fs = _mesa_CreateShaderObjectARB(GL_FRAGMENT_SHADER);
>> +   _mesa_ShaderSourceARB(fs, 1, &fs_source, NULL);
>> +   _mesa_CompileShaderARB(fs);
>> +
>> +   clear->ShaderProg = _mesa_CreateProgramObjectARB();
>> +   _mesa_AttachShader(clear->ShaderProg, fs);
>> +   _mesa_AttachShader(clear->ShaderProg, vs);
>> +   _mesa_BindAttribLocationARB(clear->ShaderProg, 0, "position");
>> +   _mesa_LinkProgramARB(clear->ShaderProg);
>> +
>> +   _mesa_DeleteShader(fs);
>> +   _mesa_DeleteShader(vs);
>> +
>> +   clear->ColorLocation = _mesa_GetUniformLocationARB(clear->ShaderProg,
>> +						      "color");
>> +}
>> +
>> +/**
>> + * Meta implementation of ctx->Driver.Clear() in terms of polygon rendering.
>> + */
>> +void
>> +_mesa_meta_glsl_Clear(struct gl_context *ctx, GLbitfield buffers)
>> +{
>> +   struct clear_state *clear = &ctx->Meta->Clear;
>> +   /* save all state but scissor, pixel pack/unpack */
>> +   GLbitfield metaSave = (META_ALL -
>> +			  META_SCISSOR -
>> +			  META_PIXEL_STORE -
>> +			  META_CONDITIONAL_RENDER);
>> +   const GLuint stencilMax = (1 << ctx->DrawBuffer->Visual.stencilBits) - 1;
>> +   struct gl_framebuffer *fb = ctx->DrawBuffer;
>> +   const float x0 = ((float)fb->_Xmin / fb->Width) * 2.0 - 1.0;
>> +   const float y0 = ((float)fb->_Ymin / fb->Height) * 2.0 - 1.0;
>> +   const float x1 = ((float)fb->_Xmax / fb->Width) * 2.0 - 1.0;
>> +   const float y1 = ((float)fb->_Ymax / fb->Height) * 2.0 - 1.0;
>> +   const float z = -invert_z(ctx->Depth.Clear);
>> +   struct vertex {
>> +      GLfloat x, y, z;
>> +   } verts[4];
>> +
>> +   metaSave = (META_ALPHA_TEST |
>> +	       META_BLEND |
>> +	       META_DEPTH_TEST |
>> +	       META_RASTERIZATION |
>> +	       META_SHADER |
>> +	       META_STENCIL_TEST |
>> +	       META_VERTEX |
>> +	       META_VIEWPORT |
>> +	       META_CLAMP_FRAGMENT_COLOR);
> 
> Why is metaSave initialized twice?

Yeah, that seems like a copy and paste bug.

> Also, BITS - OTHER_BITS - MORE_BITS
> is non-obvious.  This should result in the same compile-time constant as
> BITS & ~(OTHER_BITS | MORE_BITS), right?

I agree, it's confusing.  Copy and pasted from the original clear code.
 And yes, that should be equivalent.

--Kenneth