[Mesa-dev] [PATCH 2/3] mesa: Avoid computing fixed function texture state setup if possible.

[Eric Anholt]

None of the consumers of this state will be called while the fs or vs
is in place, and the update_texture_state() call will get re-called on
fs/vs change, so it should be safe to skip the computation.  Improves
the performance of a VS state change microbenchmark by 1.60186% +/-
0.443318% (n=20).

v2: Add comments explaining the flow of state to these two functions.
---
 src/mesa/main/texstate.c |  133 +++++++++++++++++++++++++++++----------------
 1 files changed, 86 insertions(+), 47 deletions(-)

diff --git a/src/mesa/main/texstate.c b/src/mesa/main/texstate.c
index 187ec9c..641e1f8 100644
--- a/src/mesa/main/texstate.c
+++ b/src/mesa/main/texstate.c
@@ -476,6 +476,84 @@ update_tex_combine(struct gl_context *ctx, struct gl_texture_unit *texUnit)
    }
 }
 
+/**
+ * Sets up the computed texture combiner state to be used by the fixed function
+ * fragment program, and the texture coordinates used by the fixed function
+ * fragment program, for use in setting up the fixed function vertex program.
+ *
+ * Thus, this has to come after _ReallyEnabled setup, but before
+ * update_ffvs_texture_state().
+ */
+static void
+update_fffs_texture_state(struct gl_context *ctx)
+{
+   GLuint unit;
+
+   ctx->Texture._EnabledUnits = 0;
+   ctx->Texture._EnabledCoordUnits = 0;
+
+   for (unit = 0; unit < ctx->Const.MaxCombinedTextureImageUnits; unit++) {
+      struct gl_texture_unit *texUnit = &ctx->Texture.Unit[unit];
+
+      if (!texUnit->_ReallyEnabled)
+	 continue;
+
+      ctx->Texture._EnabledUnits |= (1 << unit);
+      ctx->Texture._EnabledCoordUnits |= (1 << unit);
+
+      update_tex_combine(ctx, texUnit);
+   }
+}
+
+/**
+ * Sets up the computed fixed function vertex program state for texturing by the
+ * fragment shader, which is all about choosing what texture coordinates we need
+ * as vertex outputs and how to compute them.
+ *
+ * This relies on the choice of texture units (_ReallyEnabled) and the choice of
+ * texture coordinates needed as FS inputs (_EnabledCoordUnits).
+ */
+static void
+update_ffvs_texture_state(struct gl_context *ctx)
+{
+   GLuint unit;
+
+   ctx->Texture._GenFlags = 0x0;
+   ctx->Texture._TexMatEnabled = 0x0;
+   ctx->Texture._TexGenEnabled = 0x0;
+
+   /* Setup texgen for those texture coordinate sets that are in use */
+   for (unit = 0; unit < ctx->Const.MaxTextureCoordUnits; unit++) {
+      struct gl_texture_unit *texUnit = &ctx->Texture.Unit[unit];
+
+      texUnit->_GenFlags = 0x0;
+
+      if (!(ctx->Texture._EnabledCoordUnits & (1 << unit)))
+	 continue;
+
+      if (texUnit->TexGenEnabled) {
+	 if (texUnit->TexGenEnabled & S_BIT) {
+	    texUnit->_GenFlags |= texUnit->GenS._ModeBit;
+	 }
+	 if (texUnit->TexGenEnabled & T_BIT) {
+	    texUnit->_GenFlags |= texUnit->GenT._ModeBit;
+	 }
+	 if (texUnit->TexGenEnabled & R_BIT) {
+	    texUnit->_GenFlags |= texUnit->GenR._ModeBit;
+	 }
+	 if (texUnit->TexGenEnabled & Q_BIT) {
+	    texUnit->_GenFlags |= texUnit->GenQ._ModeBit;
+	 }
+
+	 ctx->Texture._TexGenEnabled |= ENABLE_TEXGEN(unit);
+	 ctx->Texture._GenFlags |= texUnit->_GenFlags;
+      }
+
+      ASSERT(unit < Elements(ctx->TextureMatrixStack));
+      if (ctx->TextureMatrixStack[unit].Top->type != MATRIX_IDENTITY)
+	 ctx->Texture._TexMatEnabled |= ENABLE_TEXMAT(unit);
+   }
+}
 
 /**
  * \note This routine refers to derived texture matrix values to
@@ -491,7 +569,6 @@ update_texture_state( struct gl_context *ctx )
    GLuint unit;
    struct gl_program *fprog = NULL;
    struct gl_program *vprog = NULL;
-   GLbitfield enabledFragUnits = 0x0;
 
    if (ctx->Shader.CurrentVertexProgram &&
        ctx->Shader.CurrentVertexProgram->LinkStatus) {
@@ -518,11 +595,6 @@ update_texture_state( struct gl_context *ctx )
    /* TODO: only set this if there are actual changes */
    ctx->NewState |= _NEW_TEXTURE;
 
-   ctx->Texture._EnabledUnits = 0x0;
-   ctx->Texture._GenFlags = 0x0;
-   ctx->Texture._TexMatEnabled = 0x0;
-   ctx->Texture._TexGenEnabled = 0x0;
-
    /*
     * Update texture unit state.
     */
@@ -601,59 +673,26 @@ update_texture_state( struct gl_context *ctx )
             continue;
          }
       }
-
-      /* if we get here, we know this texture unit is enabled */
-
-      ctx->Texture._EnabledUnits |= (1 << unit);
-
-      if (enabledFragTargets)
-         enabledFragUnits |= (1 << unit);
-
-      update_tex_combine(ctx, texUnit);
    }
 
 
    /* Determine which texture coordinate sets are actually needed */
    if (fprog) {
       const GLuint coordMask = (1 << MAX_TEXTURE_COORD_UNITS) - 1;
+      /* Note that this gets consumed by update_ffvs_texture_state(). */
       ctx->Texture._EnabledCoordUnits
          = (fprog->InputsRead >> FRAG_ATTRIB_TEX0) & coordMask;
    }
    else {
-      ctx->Texture._EnabledCoordUnits = enabledFragUnits;
+      update_fffs_texture_state(ctx);
    }
 
-   /* Setup texgen for those texture coordinate sets that are in use */
-   for (unit = 0; unit < ctx->Const.MaxTextureCoordUnits; unit++) {
-      struct gl_texture_unit *texUnit = &ctx->Texture.Unit[unit];
-
-      texUnit->_GenFlags = 0x0;
-
-      if (!(ctx->Texture._EnabledCoordUnits & (1 << unit)))
-	 continue;
-
-      if (texUnit->TexGenEnabled) {
-	 if (texUnit->TexGenEnabled & S_BIT) {
-	    texUnit->_GenFlags |= texUnit->GenS._ModeBit;
-	 }
-	 if (texUnit->TexGenEnabled & T_BIT) {
-	    texUnit->_GenFlags |= texUnit->GenT._ModeBit;
-	 }
-	 if (texUnit->TexGenEnabled & R_BIT) {
-	    texUnit->_GenFlags |= texUnit->GenR._ModeBit;
-	 }
-	 if (texUnit->TexGenEnabled & Q_BIT) {
-	    texUnit->_GenFlags |= texUnit->GenQ._ModeBit;
-	 }
-
-	 ctx->Texture._TexGenEnabled |= ENABLE_TEXGEN(unit);
-	 ctx->Texture._GenFlags |= texUnit->_GenFlags;
-      }
-
-      ASSERT(unit < Elements(ctx->TextureMatrixStack));
-      if (ctx->TextureMatrixStack[unit].Top->type != MATRIX_IDENTITY)
-	 ctx->Texture._TexMatEnabled |= ENABLE_TEXMAT(unit);
-   }
+   /* Skip texgen and texmat computed state setup in the presence of a vertex
+    * program.  Those state flags are only used in the case of fixed function
+    * vertex shading, in the tnl pipeline or ff_vertex_shader.
+    */
+   if (!vprog)
+      update_ffvs_texture_state(ctx);
 }
 
 
-- 
1.7.9