[Mesa-dev] [PATCH 3/3] st/mesa: For vertex shaders, don't emit saturate when SM 3.0 is unsupported

[Abdiel Janulgue]

There is a bug in the current lowering pass implementation where we lower saturate
to clamp only for vertex shaders on drivers supporting SM 3.0. The correct behavior
is to actually lower to clamp only when we don't support saturate which happens
on drivers that don't support SM 3.0

Reviewed-by: Marek Olšák <marek.olsak at amd.com>
Signed-off-by: Abdiel Janulgue <abdiel.janulgue at linux.intel.com>
---
 src/mesa/state_tracker/st_context.c        | 2 ++
 src/mesa/state_tracker/st_glsl_to_tgsi.cpp | 5 +----
 2 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/src/mesa/state_tracker/st_context.c b/src/mesa/state_tracker/st_context.c
index 1723513..9da0c77 100644
--- a/src/mesa/state_tracker/st_context.c
+++ b/src/mesa/state_tracker/st_context.c
@@ -271,6 +271,8 @@ st_create_context_priv( struct gl_context *ctx, struct pipe_context *pipe,
     */
    st->ctx->Point.MaxSize = MAX2(ctx->Const.MaxPointSize,
                                  ctx->Const.MaxPointSizeAA);
+   /* For vertex shaders, make sure not to emit saturate when SM 3.0 is not supported */
+   ctx->Const.ShaderCompilerOptions[MESA_SHADER_VERTEX].EmitNoSat = !st->has_shader_model3;
 
    _mesa_compute_version(ctx);
 
diff --git a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
index fd51595..80dd102 100644
--- a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
+++ b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
@@ -5419,9 +5419,6 @@ st_link_shader(struct gl_context *ctx, struct gl_shader_program *prog)
       if (!pscreen->get_param(pscreen, PIPE_CAP_TEXTURE_GATHER_OFFSETS))
          lower_offset_arrays(ir);
       do_mat_op_to_vec(ir);
-      /* Emit saturates in the vertex shader only if SM 3.0 is supported. */
-      bool vs_sm3 = (_mesa_shader_stage_to_program(prog->_LinkedShaders[i]->Stage) ==
-                         GL_VERTEX_PROGRAM_ARB) && st_context(ctx)->has_shader_model3;
       lower_instructions(ir,
                          MOD_TO_FRACT |
                          DIV_TO_MUL_RCP |
@@ -5432,7 +5429,7 @@ st_link_shader(struct gl_context *ctx, struct gl_shader_program *prog)
                          BORROW_TO_ARITH |
                          (options->EmitNoPow ? POW_TO_EXP2 : 0) |
                          (!ctx->Const.NativeIntegers ? INT_DIV_TO_MUL_RCP : 0) |
-                         (vs_sm3 ? SAT_TO_CLAMP : 0));
+                         (options->EmitNoSat ? SAT_TO_CLAMP : 0));
 
       lower_ubo_reference(prog->_LinkedShaders[i], ir);
       do_vec_index_to_cond_assign(ir);
-- 
1.9.1