[Mesa-dev] [PATCH] glsl_to_tgsi: invert gl_SamplePosition.y for the default framebuffer

[Marek Olšák]

From: Marek Olšák <marek.olsak at amd.com>

Fixes dEQP-GLES31.functional.shaders.sample_variables.sample_pos.correctness.default_framebuffer
with --deqp-gl-config-name=rgba8888d24s8ms4

Cc: 18.1 18.2 <mesa-stable at lists.freedesktop.org>
---
 src/mesa/state_tracker/st_glsl_to_tgsi.cpp | 35 +++++++++++++++++++++-
 1 file changed, 34 insertions(+), 1 deletion(-)

diff --git a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
index ffaaeff77a5..b7e672675d1 100644
--- a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
+++ b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
@@ -6258,20 +6258,48 @@ compile_tgsi_instruction(struct st_translate *t,
 
    default:
       ureg_insn(ureg,
                 inst->op,
                 dst, num_dst,
                 src, num_src, inst->precise);
       break;
    }
 }
 
+/* Invert SamplePos.y when rendering to the default framebuffer. */
+static void
+emit_samplepos_adjustment(struct st_translate *t, int wpos_y_transform)
+{
+   struct ureg_program *ureg = t->ureg;
+
+   assert(wpos_y_transform >= 0);
+   struct ureg_src trans_const = ureg_DECL_constant(ureg, wpos_y_transform);
+   struct ureg_src samplepos_sysval = t->systemValues[SYSTEM_VALUE_SAMPLE_POS];
+   struct ureg_dst samplepos_flipped = ureg_DECL_temporary(ureg);
+   struct ureg_dst is_fbo = ureg_DECL_temporary(ureg);
+
+   ureg_ADD(ureg, ureg_writemask(samplepos_flipped, TGSI_WRITEMASK_Y),
+            ureg_imm1f(ureg, 1), ureg_negate(samplepos_sysval));
+
+   /* If trans.x == 1, use samplepos.y, else use 1 - samplepos.y. */
+   ureg_FSEQ(ureg, ureg_writemask(is_fbo, TGSI_WRITEMASK_Y),
+             ureg_scalar(trans_const, TGSI_SWIZZLE_X), ureg_imm1f(ureg, 1));
+   ureg_UCMP(ureg, ureg_writemask(samplepos_flipped, TGSI_WRITEMASK_Y),
+             ureg_src(is_fbo), samplepos_sysval, ureg_src(samplepos_flipped));
+   ureg_MOV(ureg, ureg_writemask(samplepos_flipped, TGSI_WRITEMASK_X),
+            samplepos_sysval);
+
+   /* Use the result in place of the system value. */
+   t->systemValues[SYSTEM_VALUE_SAMPLE_POS] = ureg_src(samplepos_flipped);
+}
+
+
 /**
  * Emit the TGSI instructions for inverting and adjusting WPOS.
  * This code is unavoidable because it also depends on whether
  * a FBO is bound (STATE_FB_WPOS_Y_TRANSFORM).
  */
 static void
 emit_wpos_adjustment(struct gl_context *ctx,
                      struct st_translate *t,
                      int wpos_transform_const,
                      boolean invert,
@@ -6825,20 +6853,24 @@ st_translate_program(
                            t->systemValues[i]);
                   t->systemValues[i] = ureg_scalar(ureg_src(temp), 0);
                }
             }
 
             if (procType == PIPE_SHADER_FRAGMENT &&
                 semName == TGSI_SEMANTIC_POSITION)
                emit_wpos(st_context(ctx), t, proginfo, ureg,
                          program->wpos_transform_const);
 
+            if (procType == PIPE_SHADER_FRAGMENT &&
+                semName == TGSI_SEMANTIC_SAMPLEPOS)
+               emit_samplepos_adjustment(t, program->wpos_transform_const);
+
             sysInputs &= ~(1ull << i);
          }
       }
    }
 
    t->array_sizes = program->array_sizes;
    t->input_decls = program->inputs;
    t->num_input_decls = program->num_inputs;
    t->output_decls = program->outputs;
    t->num_output_decls = program->num_outputs;
@@ -7136,21 +7168,22 @@ get_mesa_program_tgsi(struct gl_context *ctx,
                              &prog->info.patch_outputs_written);
    count_resources(v, prog);
 
    /* The GLSL IR won't be needed anymore. */
    ralloc_free(shader->ir);
    shader->ir = NULL;
 
    /* This must be done before the uniform storage is associated. */
    if (shader->Stage == MESA_SHADER_FRAGMENT &&
        (prog->info.inputs_read & VARYING_BIT_POS ||
-        prog->info.system_values_read & (1ull << SYSTEM_VALUE_FRAG_COORD))) {
+        prog->info.system_values_read & (1ull << SYSTEM_VALUE_FRAG_COORD) ||
+        prog->info.system_values_read & (1ull << SYSTEM_VALUE_SAMPLE_POS))) {
       static const gl_state_index16 wposTransformState[STATE_LENGTH] = {
          STATE_INTERNAL, STATE_FB_WPOS_Y_TRANSFORM
       };
 
       v->wpos_transform_const = _mesa_add_state_reference(prog->Parameters,
                                                           wposTransformState);
    }
 
    /* Avoid reallocation of the program parameter list, because the uniform
     * storage is only associated with the original parameter list.
-- 
2.17.1