driconf, glsl: Add a vs_position_always_precise option

This is basically the same workaround as in 9b577f2a88 (driconf, glsl: Add a
vs_position_always_invariant option) commit but for tesselation evaluation
shaders. Some applications do not mark outputs as precise in tesselation
evaluation shaders which can lead to different results in case some
optimizations were applied.

Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
Signed-off-by: Vadym Shovkoplias <vadym.shovkoplias@globallogic.com>
Fixes: 09705747d7 ("nir/algebraic: Reassociate fadd into fmul in DPH-like pattern")
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/13027>

src/compiler/glsl/builtin_variables.cpp

@@ -1630,6 +1630,9 @@ builtin_variable_generator::generate_varyings()
 
          var->data.invariant = fields[i].location == VARYING_SLOT_POS &&
                                options->PositionAlwaysInvariant;
+
+         var->data.precise = fields[i].location == VARYING_SLOT_POS &&
+                               options->PositionAlwaysPrecise;
       }
    }
 }

src/gallium/auxiliary/pipe-loader/driinfo_gallium.h

@@ -48,6 +48,7 @@ DRI_CONF_SECTION_MISCELLANEOUS
    DRI_CONF_ALWAYS_HAVE_DEPTH_BUFFER(false)
    DRI_CONF_GLSL_ZERO_INIT(false)
    DRI_CONF_VS_POSITION_ALWAYS_INVARIANT(false)
+   DRI_CONF_VS_POSITION_ALWAYS_PRECISE(false)
    DRI_CONF_ALLOW_RGB10_CONFIGS(true)
    DRI_CONF_ALLOW_FP16_CONFIGS(false)
    DRI_CONF_FORCE_INTEGER_TEX_NEAREST(false)

src/gallium/auxiliary/util/u_driconf.c

@@ -54,6 +54,7 @@ u_driconf_fill_st_options(struct st_config_options *options,
    query_bool_option(glsl_zero_init);
    query_bool_option(force_integer_tex_nearest);
    query_bool_option(vs_position_always_invariant);
+   query_bool_option(vs_position_always_precise);
    query_bool_option(force_glsl_abs_sqrt);
    query_bool_option(allow_glsl_cross_stage_interpolation_mismatch);
    query_bool_option(allow_draw_out_of_order);

src/gallium/include/frontend/api.h

@@ -230,6 +230,7 @@ struct st_config_options
    bool glsl_ignore_write_to_readonly_var;
    bool glsl_zero_init;
    bool vs_position_always_invariant;
+   bool vs_position_always_precise;
    bool force_glsl_abs_sqrt;
    bool allow_glsl_cross_stage_interpolation_mismatch;
    bool allow_draw_out_of_order;

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

@@ -95,6 +95,7 @@ static const driOptionDescription brw_driconf[] = {
    DRI_CONF_SECTION_MISCELLANEOUS
       DRI_CONF_GLSL_ZERO_INIT(false)
       DRI_CONF_VS_POSITION_ALWAYS_INVARIANT(false)
+      DRI_CONF_VS_POSITION_ALWAYS_PRECISE(false)
       DRI_CONF_ALLOW_RGB10_CONFIGS(false)
       DRI_CONF_ALLOW_RGB565_CONFIGS(true)
       DRI_CONF_ALLOW_FP16_CONFIGS(false)
@@ -2803,6 +2804,7 @@ __DRIconfig **brw_init_screen(__DRIscreen *dri_screen)
       !(screen->kernel_features & KERNEL_ALLOWS_CONTEXT_ISOLATION);
 
    screen->compiler->glsl_compiler_options[MESA_SHADER_VERTEX].PositionAlwaysInvariant = driQueryOptionb(&screen->optionCache, "vs_position_always_invariant");
+   screen->compiler->glsl_compiler_options[MESA_SHADER_TESS_EVAL].PositionAlwaysPrecise = driQueryOptionb(&screen->optionCache, "vs_position_always_precise");
 
    screen->compiler->supports_pull_constants = true;
    screen->compiler->compact_params = true;

src/mesa/main/mtypes.h

@@ -3295,6 +3295,9 @@ struct gl_shader_compiler_options
    /** (driconf) Force gl_Position to be considered invariant */
    GLboolean PositionAlwaysInvariant;
 
+   /** (driconf) Force gl_Position to be considered precise */
+   GLboolean PositionAlwaysPrecise;
+
    const struct nir_shader_compiler_options *NirOptions;
 };
 

src/mesa/state_tracker/st_context.c

@@ -796,6 +796,8 @@ st_create_context_priv(struct gl_context *ctx, struct pipe_context *pipe,
 
    ctx->Const.ShaderCompilerOptions[MESA_SHADER_VERTEX].PositionAlwaysInvariant = options->vs_position_always_invariant;
 
+   ctx->Const.ShaderCompilerOptions[MESA_SHADER_TESS_EVAL].PositionAlwaysPrecise = options->vs_position_always_precise;
+
    enum pipe_shader_ir preferred_ir = (enum pipe_shader_ir)
       screen->get_shader_param(screen, PIPE_SHADER_VERTEX,
                                PIPE_SHADER_CAP_PREFERRED_IR);

src/util/driconf.h

@@ -359,6 +359,10 @@
    DRI_CONF_OPT_B(vs_position_always_invariant, def, \
                   "Force the vertex shader's gl_Position output to be considered 'invariant'")
 
+#define DRI_CONF_VS_POSITION_ALWAYS_PRECISE(def) \
+   DRI_CONF_OPT_B(vs_position_always_precise, def, \
+                  "Force the vertex shader's gl_Position output to be considered 'precise'")
+
 #define DRI_CONF_ALLOW_RGB10_CONFIGS(def) \
    DRI_CONF_OPT_B(allow_rgb10_configs, def, \
                   "Allow exposure of visuals and fbconfigs with rgb10a2 formats")