On 06/15/2011 08:27 AM, Eric Anholt wrote:
On Wed, 15 Jun 2011 01:24:54 -0700, Kenneth Graunke<kenn...@whitecape.org>  
wrote:
Gen4-6 don't have a sample_d_c message, so we have to do a regular
sample_d and emit instructions to manually perform the comparison.

This requires a state dependent recompile whenever ctx->Depth.Func
changes.  do_wm_prog looks for a compiled program in the cache based off
of brw_wm_prog_key, and if it doesn't find one, recompiles.  So we
simply need to add the depth comparison function to the key; the
_NEW_DEPTH dirty bit was already in-place.

diff --git a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp 
b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
index 03687ce..67344bd 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
@@ -744,7 +744,7 @@ fs_visitor::emit_texture_gen5(ir_texture *ir, fs_reg dst, 
fs_reg coordinate,
     }
     mlen += ir->coordinate->type->vector_elements * reg_width;

-   if (ir->shadow_comparitor) {
+   if (ir->shadow_comparitor&&  ir->op != ir_txd) {
        mlen = MAX2(mlen, header_present + 4 * reg_width);

        this->result = reg_undef;
@@ -934,6 +934,21 @@ fs_visitor::visit(ir_texture *ir)
     int sampler = _mesa_get_sampler_uniform_value(ir->sampler, prog,&fp->Base);
     sampler = fp->Base.SamplerUnits[sampler];

+   /* Pre-Ivybridge doesn't have a sample_d_c message, so shadow compares
+    * for textureGrad/TXD need to be emulated with instructions.
+    */
+   bool hw_compare_supported = ir->op != ir_txd || intel->gen>  7;
+   if (ir->shadow_comparitor&&  !hw_compare_supported) {
+      /* Mark that this program is only valid for the current glDepthFunc */
+      c->key.depth_compare_func = ctx->Depth.Func;

The compiler is only called if the key wasn't found in the cache, so you
can't set the key inside the compiler :)

You're right, of course. Unfortunately, I really want to! Only shaders using shadow2DGradARB need to be recompiled when glDepthFunc changes, so I really want to leave it as 0 for most shaders. Otherwise the common case will have completely pointless recompiles.

Unfortunately, I only know whether or not I need it at compile time...

This -almost- works...it just means we'll recompile shaders using shadow2DGradARB every time, since they'll never be found in the cache. Stupid. I'll reply with a patch which works around this.

+
+      /* No need to even sample for GL_ALWAYS or GL_NEVER...bail early */
+      if (ctx->Depth.Func == GL_ALWAYS)
+        return swizzle_shadow_result(ir, fs_reg(1.0f), sampler);
+      else if (ctx->Depth.Func == GL_NEVER)
+        return swizzle_shadow_result(ir, fs_reg(0.0f), sampler);
+   }

Generally I use "c->key." values to make it obvious that state dependent
recompiles are in place, instead of "ctx->".

Good idea.  Updated.

diff --git a/src/mesa/drivers/dri/i965/brw_wm.h 
b/src/mesa/drivers/dri/i965/brw_wm.h
index e244b55..0b284b6 100644
--- a/src/mesa/drivers/dri/i965/brw_wm.h
+++ b/src/mesa/drivers/dri/i965/brw_wm.h
@@ -67,6 +67,7 @@ struct brw_wm_prog_key {
     GLuint alpha_test:1;
     GLuint clamp_fragment_color:1;
     GLuint line_aa:2;
+   uint8_t depth_compare_func; /* 0 if irrelevant, GL_LESS etc. otherwise */

Wow, those do happen to fit in 8 bits.  Might comment that explicitly --
leaving out bits when storing GLenums has been a common bug and seeing
things like this make me paranoid and go check :)

:) Makes sense; commented.  I figured we really want to pack the key.
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