mesa: optimize the dual source blend error checking using a bitmask

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/i965/brw_wm.c

@@ -480,7 +480,7 @@ brw_wm_populate_key(struct brw_context *brw, struct brw_wm_prog_key *key)
 
    /* _NEW_COLOR */
    key->force_dual_color_blend = brw->dual_color_blend_by_location &&
-      (ctx->Color.BlendEnabled & 1) && ctx->Color.Blend[0]._UsesDualSrc;
+      (ctx->Color.BlendEnabled & 1) && ctx->Color._BlendUsesDualSrc & 0x1;
 
    /* _NEW_MULTISAMPLE, _NEW_BUFFERS */
    key->alpha_to_coverage =  _mesa_is_alpha_to_coverage_enabled(ctx);

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

@@ -1942,7 +1942,7 @@ genX(upload_wm)(struct brw_context *brw)
 #if GEN_GEN == 6
       wm.DualSourceBlendEnable =
          wm_prog_data->dual_src_blend && (ctx->Color.BlendEnabled & 1) &&
-         ctx->Color.Blend[0]._UsesDualSrc;
+         ctx->Color._BlendUsesDualSrc & 0x1;
       wm.oMaskPresenttoRenderTarget = wm_prog_data->uses_omask;
       wm.NumberofSFOutputAttributes = wm_prog_data->num_varying_inputs;
 
@@ -2885,7 +2885,7 @@ set_blend_entry_bits(struct brw_context *brw, BLEND_ENTRY_GENXML *entry, int i,
        * We override SRC1_ALPHA to ONE and ONE_MINUS_SRC1_ALPHA to ZERO,
        * and leave it enabled anyway.
        */
-      if (GEN_GEN >= 6 && ctx->Color.Blend[i]._UsesDualSrc && alpha_to_one) {
+      if (GEN_GEN >= 6 && ctx->Color._BlendUsesDualSrc & (1 << i) && alpha_to_one) {
          srcRGB = fix_dual_blend_alpha_to_one(srcRGB);
          srcA = fix_dual_blend_alpha_to_one(srcA);
          dstRGB = fix_dual_blend_alpha_to_one(dstRGB);
@@ -2910,7 +2910,7 @@ set_blend_entry_bits(struct brw_context *brw, BLEND_ENTRY_GENXML *entry, int i,
        * so we just disable the blending to prevent possible issues.
        */
       entry->ColorBufferBlendEnable =
-         !ctx->Color.Blend[0]._UsesDualSrc || wm_prog_data->dual_src_blend;
+         !(ctx->Color._BlendUsesDualSrc & 0x1) || wm_prog_data->dual_src_blend;
 
       entry->DestinationBlendFactor = blend_factor(dstRGB);
       entry->SourceBlendFactor = blend_factor(srcRGB);
@@ -3926,7 +3926,7 @@ genX(upload_ps)(struct brw_context *brw)
        */
       ps.DualSourceBlendEnable = prog_data->dual_src_blend &&
                                  (ctx->Color.BlendEnabled & 1) &&
-                                 ctx->Color.Blend[0]._UsesDualSrc;
+                                 ctx->Color._BlendUsesDualSrc & 0x1;
 
       /* BRW_NEW_FS_PROG_DATA */
       ps.AttributeEnable = (prog_data->num_varying_inputs != 0);
@@ -4818,7 +4818,7 @@ genX(upload_ps_blend)(struct brw_context *brw)
          /* Alpha to One doesn't work with Dual Color Blending.  Override
           * SRC1_ALPHA to ONE and ONE_MINUS_SRC1_ALPHA to ZERO.
           */
-         if (alpha_to_one && color->Blend[0]._UsesDualSrc) {
+         if (alpha_to_one && color->_BlendUsesDualSrc & 0x1) {
             srcRGB = fix_dual_blend_alpha_to_one(srcRGB);
             srcA = fix_dual_blend_alpha_to_one(srcA);
             dstRGB = fix_dual_blend_alpha_to_one(dstRGB);
@@ -4843,7 +4843,7 @@ genX(upload_ps_blend)(struct brw_context *brw)
           * so we just disable the blending to prevent possible issues.
           */
          pb.ColorBufferBlendEnable =
-            !color->Blend[0]._UsesDualSrc || wm_prog_data->dual_src_blend;
+            !(color->_BlendUsesDualSrc & 0x1) || wm_prog_data->dual_src_blend;
          pb.SourceAlphaBlendFactor = brw_translate_blend_factor(srcA);
          pb.DestinationAlphaBlendFactor = brw_translate_blend_factor(dstA);
          pb.SourceBlendFactor = brw_translate_blend_factor(srcRGB);

src/mesa/main/blend.c

@@ -168,7 +168,7 @@ blend_factor_is_dual_src(GLenum factor)
 	   factor == GL_ONE_MINUS_SRC1_ALPHA);
 }
 
-static void
+static bool
 update_uses_dual_src(struct gl_context *ctx, int buf)
 {
    bool uses_dual_src =
@@ -177,10 +177,14 @@ update_uses_dual_src(struct gl_context *ctx, int buf)
        blend_factor_is_dual_src(ctx->Color.Blend[buf].SrcA) ||
        blend_factor_is_dual_src(ctx->Color.Blend[buf].DstA));
 
-   if (ctx->Color.Blend[buf]._UsesDualSrc != uses_dual_src) {
+   if (((ctx->Color._BlendUsesDualSrc >> buf) & 0x1) != uses_dual_src) {
-      ctx->Color.Blend[buf]._UsesDualSrc = uses_dual_src;
+      if (uses_dual_src)
-      _mesa_update_valid_to_render_state(ctx);
+         ctx->Color._BlendUsesDualSrc |= 1 << buf;
+      else
+         ctx->Color._BlendUsesDualSrc &= ~(1 << buf);
+      return true; /* changed state */
    }
+   return false; /* no change */
 }
 
 
@@ -247,10 +251,16 @@ blend_func_separate(struct gl_context *ctx,
       ctx->Color.Blend[buf].DstA = dfactorA;
    }
 
+   GLbitfield old_blend_uses_dual_src = ctx->Color._BlendUsesDualSrc;
    update_uses_dual_src(ctx, 0);
-   for (unsigned buf = 1; buf < numBuffers; buf++) {
+   /* We have to replicate the bit to all color buffers. */
-      ctx->Color.Blend[buf]._UsesDualSrc = ctx->Color.Blend[0]._UsesDualSrc;
+   if (ctx->Color._BlendUsesDualSrc & 0x1)
-   }
+      ctx->Color._BlendUsesDualSrc |= BITFIELD_RANGE(1, numBuffers - 1);
+   else
+      ctx->Color._BlendUsesDualSrc = 0;
+
+   if (ctx->Color._BlendUsesDualSrc != old_blend_uses_dual_src)
+      _mesa_update_valid_to_render_state(ctx);
 
    ctx->Color._BlendFuncPerBuffer = GL_FALSE;
 
@@ -404,7 +414,8 @@ blend_func_separatei(GLuint buf, GLenum sfactorRGB, GLenum dfactorRGB,
    ctx->Color.Blend[buf].DstRGB = dfactorRGB;
    ctx->Color.Blend[buf].SrcA = sfactorA;
    ctx->Color.Blend[buf].DstA = dfactorA;
-   update_uses_dual_src(ctx, buf);
+   if (update_uses_dual_src(ctx, buf))
+      _mesa_update_valid_to_render_state(ctx);
    ctx->Color._BlendFuncPerBuffer = GL_TRUE;
 }
 

src/mesa/main/draw_validate.c

@@ -96,11 +96,14 @@ _mesa_update_valid_to_render_state(struct gl_context *ctx)
     *     has more than the value of MAX_DUAL_SOURCE_DRAW_BUFFERS-1 active
     *     color attachements."
     */
-   for (unsigned i = ctx->Const.MaxDualSourceDrawBuffers;
+   unsigned max_dual_source_buffers = ctx->Const.MaxDualSourceDrawBuffers;
-	i < ctx->DrawBuffer->_NumColorDrawBuffers; i++) {
+   unsigned num_color_buffers = ctx->DrawBuffer->_NumColorDrawBuffers;
-      if (ctx->Color.Blend[i]._UsesDualSrc)
+
-         return;
+   if (num_color_buffers > max_dual_source_buffers &&
-   }
+       ctx->Color._BlendUsesDualSrc &
+       BITFIELD_RANGE(max_dual_source_buffers,
+                      num_color_buffers - max_dual_source_buffers))
+      return;
 
    if (ctx->Color.BlendEnabled &&
        ctx->Color._AdvancedBlendMode != BLEND_NONE) {
@@ -119,7 +122,7 @@ _mesa_update_valid_to_render_state(struct gl_context *ctx)
       if (ctx->DrawBuffer->ColorDrawBuffer[0] == GL_FRONT_AND_BACK)
          return;
 
-      for (unsigned i = 1; i < ctx->DrawBuffer->_NumColorDrawBuffers; i++) {
+      for (unsigned i = 1; i < num_color_buffers; i++) {
          if (ctx->DrawBuffer->ColorDrawBuffer[i] != GL_NONE)
             return;
       }

src/mesa/main/mtypes.h

@@ -399,12 +399,9 @@ struct gl_colorbuffer_attrib
       GLenum16 DstA;               /**< Alpha blend dest term */
       GLenum16 EquationRGB;        /**< GL_ADD, GL_SUBTRACT, etc. */
       GLenum16 EquationA;          /**< GL_ADD, GL_SUBTRACT, etc. */
-      /**
-       * Set if any blend factor uses SRC1.  Computed at the time blend factors
-       * get set.
-       */
-      GLboolean _UsesDualSrc;
    } Blend[MAX_DRAW_BUFFERS];
+   /** Bitfield of color buffers with enabled dual source blending. */
+   GLbitfield _BlendUsesDualSrc;
    /** Are the blend func terms currently different for each buffer/target? */
    GLboolean _BlendFuncPerBuffer;
    /** Are the blend equations currently different for each buffer/target? */