mesa: optimize set_varying_vp_inputs by precomputing the conditions

set_varying_vp_inputs is called every draw call, which checks
_Maintain*Program. Let's move that checking out of there.

This adds a new flag that determines whether set_varying_vp_inputs
should do anything.

All code that changes _Maintain*Program must now reinitialize the new
flag. This is done by new function _mesa_reset_vertex_processing_mode.

Reviewed-by: Zoltán Böszörményi <zboszor@gmail.com>
Reviewed-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8798>

src/mesa/drivers/dri/i915/i915_context.c

@@ -30,6 +30,7 @@
 #include "main/framebuffer.h"
 #include "main/extensions.h"
 #include "main/macros.h"
+#include "main/state.h"
 #include "main/version.h"
 #include "main/vtxfmt.h"
 #include "intel_chipset.h"
@@ -255,6 +256,7 @@ i915CreateContext(int api,
       ctx->Const.Program[MESA_SHADER_FRAGMENT].MediumInt;
 
    ctx->FragmentProgram._MaintainTexEnvProgram = true;
+   _mesa_reset_vertex_processing_mode(ctx);
 
    /* FINISHME: Are there other options that should be enabled for software
     * FINISHME: vertex shaders?

src/mesa/drivers/dri/i965/brw_context.c

@@ -1127,6 +1127,7 @@ brwCreateContext(gl_api api,
 
    ctx->VertexProgram._MaintainTnlProgram = true;
    ctx->FragmentProgram._MaintainTexEnvProgram = true;
+   _mesa_reset_vertex_processing_mode(ctx);
 
    brw_draw_init( brw );
 

src/mesa/drivers/x11/xm_api.c

@@ -71,6 +71,7 @@
 #include "main/framebuffer.h"
 #include "main/macros.h"
 #include "main/renderbuffer.h"
+#include "main/state.h"
 #include "main/teximage.h"
 #include "main/version.h"
 #include "main/vtxfmt.h"
@@ -920,6 +921,7 @@ XMesaContext XMesaCreateContext( XMesaVisual v, XMesaContext share_list )
    if (0) {
       mesaCtx->VertexProgram._MaintainTnlProgram = GL_TRUE;
       mesaCtx->FragmentProgram._MaintainTexEnvProgram = GL_TRUE;
+      _mesa_reset_vertex_processing_mode(ctx);
    }
 
    _mesa_enable_sw_extensions(mesaCtx);

src/mesa/main/context.c

@@ -1247,6 +1247,7 @@ _mesa_initialize_context(struct gl_context *ctx,
    if (ctx->VertexProgram._MaintainTnlProgram) {
       /* this is required... */
       ctx->FragmentProgram._MaintainTexEnvProgram = GL_TRUE;
+      _mesa_reset_vertex_processing_mode(ctx);
    }
 
    /* Mesa core handles all the formats that mesa core knows about.
@@ -1287,6 +1288,7 @@ _mesa_initialize_context(struct gl_context *ctx,
    case API_OPENGLES2:
       ctx->FragmentProgram._MaintainTexEnvProgram = GL_TRUE;
       ctx->VertexProgram._MaintainTnlProgram = GL_TRUE;
+      _mesa_reset_vertex_processing_mode(ctx);
       break;
    }
 

src/mesa/main/mtypes.h

@@ -2382,6 +2382,8 @@ struct gl_vertex_program_state
 
    GLboolean _Overriden;
 
+   bool _VPModeOptimizesConstantAttribs;
+
    /**
     * If we have a vertex program, a TNL program or no program at all.
     * Note that this value should be kept up to date all the time,

src/mesa/main/state.c

@@ -571,19 +571,8 @@ _mesa_update_state( struct gl_context *ctx )
 static void
 set_varying_vp_inputs(struct gl_context *ctx, GLbitfield varying_inputs)
 {
-   /*
+   if (ctx->VertexProgram._VPModeOptimizesConstantAttribs &&
-    * The gl_context::varying_vp_inputs value is only used when in
+       ctx->varying_vp_inputs != varying_inputs) {
-    * VP_MODE_FF mode.
-    */
-   if (VP_MODE_FF != ctx->VertexProgram._VPMode)
-      return;
-
-   /* Only fixed-func generated programs ever uses varying_vp_inputs. */
-   if (!ctx->VertexProgram._MaintainTnlProgram &&
-       !ctx->FragmentProgram._MaintainTexEnvProgram)
-      return;
-
-   if (ctx->varying_vp_inputs != varying_inputs) {
       ctx->varying_vp_inputs = varying_inputs;
       ctx->NewState |= _NEW_VARYING_VP_INPUTS;
    }
@@ -622,6 +611,14 @@ set_vertex_processing_mode(struct gl_context *ctx, gl_vertex_processing_mode m)
    /* Finally memorize the value */
    ctx->VertexProgram._VPMode = m;
 
+   /* The gl_context::varying_vp_inputs value is only used when in
+    * VP_MODE_FF mode and the fixed-func pipeline is emulated by shaders.
+    */
+   ctx->VertexProgram._VPModeOptimizesConstantAttribs =
+      m == VP_MODE_FF &&
+      ctx->VertexProgram._MaintainTnlProgram &&
+      ctx->FragmentProgram._MaintainTexEnvProgram;
+
    /* Since we only track the varying inputs while being in fixed function
     * vertex processing mode, we may need to recheck for the
     * _NEW_VARYING_VP_INPUTS bit.
@@ -649,6 +646,13 @@ _mesa_update_vertex_processing_mode(struct gl_context *ctx)
 }
 
 
+void
+_mesa_reset_vertex_processing_mode(struct gl_context *ctx)
+{
+   ctx->VertexProgram._VPMode = -1; /* force the update */
+   _mesa_update_vertex_processing_mode(ctx);
+}
+
 /**
  * Set the _DrawVAO and the net enabled arrays.
  * The vao->_Enabled bitmask is transformed due to position/generic0

src/mesa/main/state.h

@@ -54,6 +54,9 @@ _mesa_set_vp_override(struct gl_context *ctx, GLboolean flag);
 extern void
 _mesa_update_vertex_processing_mode(struct gl_context *ctx);
 
+extern void
+_mesa_reset_vertex_processing_mode(struct gl_context *ctx);
+
 
 /**
  * Set the _DrawVAO and the net enabled arrays.

src/mesa/program/program.c

@@ -35,6 +35,7 @@
 #include "main/hash.h"
 #include "main/macros.h"
 #include "main/shaderobj.h"
+#include "main/state.h"
 #include "program.h"
 #include "prog_cache.h"
 #include "prog_parameter.h"
@@ -100,7 +101,7 @@ _mesa_init_program(struct gl_context *ctx)
                            ctx->Shared->DefaultFragmentProgram);
    assert(ctx->FragmentProgram.Current);
    ctx->FragmentProgram.Cache = _mesa_new_program_cache();
-   ctx->VertexProgram._VPMode = VP_MODE_FF;
+   _mesa_reset_vertex_processing_mode(ctx);
 
    /* XXX probably move this stuff */
    ctx->ATIFragmentShader.Enabled = GL_FALSE;

src/mesa/state_tracker/st_context.c

@@ -33,6 +33,7 @@
 #include "main/glthread.h"
 #include "main/samplerobj.h"
 #include "main/shaderobj.h"
+#include "main/state.h"
 #include "main/version.h"
 #include "main/vtxfmt.h"
 #include "main/hash.h"
@@ -649,6 +650,7 @@ st_create_context_priv(struct gl_context *ctx, struct pipe_context *pipe,
     */
    ctx->FragmentProgram._MaintainTexEnvProgram = GL_TRUE;
    ctx->VertexProgram._MaintainTnlProgram = GL_TRUE;
+   _mesa_reset_vertex_processing_mode(ctx);
 
    if (no_error)
       ctx->Const.ContextFlags |= GL_CONTEXT_FLAG_NO_ERROR_BIT_KHR;