i965: Disable thread dispatch when the FS doesn't do any work.

This should reduce the cost of generating shadow maps, for example.
No performance difference measured in nexuiz, though it does trigger
this path.

diff --git a/src/mesa/drivers/dri/i965/brw_wm.h b/src/mesa/drivers/dri/i965/brw_wm.h
index a094c45a7e02ee6ad00b20e1afb6cbf02283b3f4..99bd15c187fb4ad01f4d220873e0c357957f0237 100644 (file)
--- a/src/mesa/drivers/dri/i965/brw_wm.h
+++ b/src/mesa/drivers/dri/i965/brw_wm.h
@@ -33,6 +33,7 @@
 #ifndef BRW_WM_H
 #define BRW_WM_H
 
+#include <stdbool.h>
 
 #include "program/prog_instruction.h"
 #include "brw_context.h"
@@ -473,4 +474,6 @@ GLboolean brw_link_shader(struct gl_context *ctx, struct gl_shader_program *prog
 struct gl_shader *brw_new_shader(struct gl_context *ctx, GLuint name, GLuint type);
 struct gl_shader_program *brw_new_shader_program(struct gl_context *ctx, GLuint name);
 
+bool brw_color_buffer_write_enabled(struct brw_context *brw);
+
 #endif

diff --git a/src/mesa/drivers/dri/i965/brw_wm_state.c b/src/mesa/drivers/dri/i965/brw_wm_state.c
index 817adefb0cc8a2ae7043c1cf308ed1f72000fa20..411204e70453382ad20eb4c6e5d880373887b572 100644 (file)
--- a/src/mesa/drivers/dri/i965/brw_wm_state.c
+++ b/src/mesa/drivers/dri/i965/brw_wm_state.c
@@ -52,9 +52,36 @@ struct brw_wm_unit_key {
    unsigned int nr_surfaces, sampler_count;
    GLboolean uses_depth, computes_depth, uses_kill, is_glsl;
    GLboolean polygon_stipple, stats_wm, line_stipple, offset_enable;
+   GLboolean color_write_enable;
    GLfloat offset_units, offset_factor;
 };
 
+bool
+brw_color_buffer_write_enabled(struct brw_context *brw)
+{
+   struct gl_context *ctx = &brw->intel.ctx;
+   const struct gl_fragment_program *fp = brw->fragment_program;
+   int i;
+
+   /* _NEW_BUFFERS */
+   for (i = 0; i < ctx->DrawBuffer->_NumColorDrawBuffers; i++) {
+      struct gl_renderbuffer *rb = ctx->DrawBuffer->_ColorDrawBuffers[i];
+
+      /* _NEW_COLOR */
+      if (rb &&
+         (fp->Base.OutputsWritten & BITFIELD64_BIT(FRAG_RESULT_COLOR) ||
+          fp->Base.OutputsWritten & BITFIELD64_BIT(FRAG_RESULT_DATA0 + i)) &&
+         (ctx->Color.ColorMask[i][0] ||
+          ctx->Color.ColorMask[i][1] ||
+          ctx->Color.ColorMask[i][2] ||
+          ctx->Color.ColorMask[i][3])) {
+        return true;
+      }
+   }
+
+   return false;
+}
+
 static void
 wm_unit_populate_key(struct brw_context *brw, struct brw_wm_unit_key *key)
 {
@@ -100,6 +127,9 @@ wm_unit_populate_key(struct brw_context *brw, struct brw_wm_unit_key *key)
    if (brw->state.depth_region == NULL)
       key->computes_depth = 0;
 
+   /* _NEW_BUFFERS | _NEW_COLOR */
+   key->color_write_enable = brw_color_buffer_write_enabled(brw);
+
    /* _NEW_COLOR */
    key->uses_kill = fp->UsesKill || ctx->Color.AlphaEnabled;
    key->is_glsl = bfp->isGLSL;
@@ -188,7 +218,13 @@ wm_unit_create_from_key(struct brw_context *brw, struct brw_wm_unit_key *key,
       wm.wm5.enable_16_pix = 1;
 
    wm.wm5.max_threads = brw->wm_max_threads - 1;
-   wm.wm5.thread_dispatch_enable = 1;  /* AKA: color_write */
+
+   if (key->color_write_enable ||
+       key->uses_kill ||
+       key->computes_depth) {
+      wm.wm5.thread_dispatch_enable = 1;
+   }
+
    wm.wm5.legacy_line_rast = 0;
    wm.wm5.legacy_global_depth_bias = 0;
    wm.wm5.early_depth_test = 1;                /* never need to disable */
@@ -293,7 +329,8 @@ const struct brw_tracked_state brw_wm_unit = {
               _NEW_POLYGONSTIPPLE | 
               _NEW_LINE | 
               _NEW_COLOR |
-              _NEW_DEPTH),
+              _NEW_DEPTH |
+              _NEW_BUFFERS),
 
       .brw = (BRW_NEW_FRAGMENT_PROGRAM | 
              BRW_NEW_CURBE_OFFSETS |

diff --git a/src/mesa/drivers/dri/i965/gen6_wm_state.c b/src/mesa/drivers/dri/i965/gen6_wm_state.c
index 7ef99eea6277c696772c2e4710660460c5d957b1..21059be9657f79ff6959a698768f3f6a9485474a 100644 (file)
--- a/src/mesa/drivers/dri/i965/gen6_wm_state.c
+++ b/src/mesa/drivers/dri/i965/gen6_wm_state.c
@@ -29,6 +29,7 @@
 #include "brw_state.h"
 #include "brw_defines.h"
 #include "brw_util.h"
+#include "brw_wm.h"
 #include "program/prog_parameter.h"
 #include "program/prog_statevars.h"
 #include "intel_batchbuffer.h"
@@ -123,7 +124,6 @@ upload_wm_state(struct brw_context *brw)
           GEN6_WM_DISPATCH_START_GRF_SHIFT_0);
 
    dw5 |= (40 - 1) << GEN6_WM_MAX_THREADS_SHIFT;
-   dw5 |= GEN6_WM_DISPATCH_ENABLE;
 
    /* BRW_NEW_FRAGMENT_PROGRAM */
    if (fp->isGLSL)
@@ -149,6 +149,11 @@ upload_wm_state(struct brw_context *brw)
    if (fp->program.UsesKill || ctx->Color.AlphaEnabled)
       dw5 |= GEN6_WM_KILL_ENABLE;
 
+   if (brw_color_buffer_write_enabled(brw) ||
+       dw5 & (GEN6_WM_KILL_ENABLE | GEN6_WM_COMPUTED_DEPTH)) {
+      dw5 |= GEN6_WM_DISPATCH_ENABLE;
+   }
+
    dw6 |= GEN6_WM_PERSPECTIVE_PIXEL_BARYCENTRIC;
 
    dw6 |= brw_count_bits(brw->fragment_program->Base.InputsRead) <<
@@ -169,7 +174,7 @@ upload_wm_state(struct brw_context *brw)
 
 const struct brw_tracked_state gen6_wm_state = {
    .dirty = {
-      .mesa  = (_NEW_LINE | _NEW_POLYGONSTIPPLE | _NEW_COLOR |
+      .mesa  = (_NEW_LINE | _NEW_POLYGONSTIPPLE | _NEW_COLOR | _NEW_BUFFERS |
                _NEW_PROGRAM_CONSTANTS),
       .brw   = (BRW_NEW_CURBE_OFFSETS |
                BRW_NEW_FRAGMENT_PROGRAM |