swrast: initial multi-threaded span rendering

Optional parallel rendering of spans using OpenMP.
Initial implementation for aa triangles. A new option for scons is
also provided to activate the openmp support (off by default).

Signed-off-by: Brian Paul <[email protected]>

1 files changed, 12 insertions, 0 deletions

diff --git a/src/mesa/tnl/t_pipeline.c b/src/mesa/tnl/t_pipeline.c
index 18f095f0d4b..881d5d5f535 100644
--- a/src/mesa/tnl/t_pipeline.c
+++ b/src/mesa/tnl/t_pipeline.c
@@ -146,7 +146,17 @@ void _tnl_run_pipeline( struct gl_context *ctx )
 	 _tnl_notify_pipeline_output_change( ctx );
    }
 
+#ifndef _OPENMP
+   /* Don't adjust FPU precision mode in case multiple threads are to be used.
+    * This would require that the additional threads also changed the FPU mode
+    * which is quite a mess as this had to be done in all parallelized sections;
+    * otherwise the master thread and all other threads are running in different
+    * modes, producing inconsistent results.
+    * Note that all x64 implementations don't define/use START_FAST_MATH, so
+    * this is "hack" is only used in i386 mode
+    */
    START_FAST_MATH(__tmp);
+#endif
 
    for (i = 0; i < tnl->pipeline.nr_stages ; i++) {
       struct tnl_pipeline_stage *s = &tnl->pipeline.stages[i];
@@ -154,7 +164,9 @@ void _tnl_run_pipeline( struct gl_context *ctx )
 	 break;
    }
 
+#ifndef _OPENMP
    END_FAST_MATH(__tmp);
+#endif
 }