Re: [Mesa-dev] [PATCH RESEND v4] glsl: enforce invariant conditions for built-in variables

[Lars Hamre]

Gentle ping. I would appreciate feedbaçk on what (if anything) I
should do to get this patch into shape.

Regards,
Lars Hamre

On Mon, Jun 6, 2016 at 9:00 AM, Lars Hamre  wrote:
> v2:
>  - ES version check (Tapani Pälli)
> v3/v4:
>  - compare varying slot locations rather than names (Ilia Mirkin)
>
> The conditions for which certain built-in special variables
> can be declared invariant were not being checked.
>
> GLSL ES 1.00 specification, Section "Invariance and linkage" says:
>
> For the built-in special variables, gl_FragCoord can
> only be declared invariant if and only if gl_Position is
> declared invariant. Similarly gl_PointCoord can only be
> declared invariant if and only if gl_PointSize is declared
> invariant. It is an error to declare gl_FrontFacing as invariant.
>
> This fixes the following piglit tests in spec/glsl-es-1.00/linker:
> glsl-fcoord-invariant
> glsl-fface-invariant
> glsl-pcoord-invariant
>
> Signed-off-by: Lars Hamre 
>
> ---
>
> NOTE: Someone with access will need to commit this after the
>   review process
>
>  src/compiler/glsl/link_varyings.cpp | 39 
> +
>  1 file changed, 39 insertions(+)
>
> diff --git a/src/compiler/glsl/link_varyings.cpp 
> b/src/compiler/glsl/link_varyings.cpp
> index 34c8906..755000e 100644
> --- a/src/compiler/glsl/link_varyings.cpp
> +++ b/src/compiler/glsl/link_varyings.cpp
> @@ -336,6 +336,9 @@ cross_validate_outputs_to_inputs(struct gl_shader_program 
> *prog,
> ir_variable *explicit_locations[MAX_VARYINGS_INCL_PATCH][4] =
>{ {NULL, NULL} };
>
> +   bool is_gl_position_invariant = false;
> +   bool is_gl_point_size_invariant = false;
> +
> /* Find all shader outputs in the "producer" stage.
>  */
> foreach_in_list(ir_instruction, node, producer->ir) {
> @@ -344,6 +347,13 @@ cross_validate_outputs_to_inputs(struct 
> gl_shader_program *prog,
>if (var == NULL || var->data.mode != ir_var_shader_out)
>   continue;
>
> +  if (prog->IsES && prog->Version < 300) {
> + if (var->data.location == VARYING_SLOT_POS)
> +is_gl_position_invariant = var->data.invariant;
> + if (var->data.location == VARYING_SLOT_PSIZ)
> +is_gl_point_size_invariant = var->data.invariant;
> +  }
> +
>if (!var->data.explicit_location
>|| var->data.location < VARYING_SLOT_VAR0)
>   parameters.add_variable(var);
> @@ -430,6 +440,35 @@ cross_validate_outputs_to_inputs(struct 
> gl_shader_program *prog,
>if (input == NULL || input->data.mode != ir_var_shader_in)
>   continue;
>
> +  /*
> +   * GLSL ES 1.00 specification, Section "Invariance and linkage" says:
> +   *
> +   *  "For the built-in special variables, gl_FragCoord can
> +   *  only be declared invariant if and only if gl_Position is
> +   *  declared invariant. Similarly gl_PointCoord can only be
> +   *  declared invariant if and only if gl_PointSize is declared
> +   *  invariant. It is an error to declare gl_FrontFacing as invariant."
> +   */
> +  if (prog->IsES && prog->Version < 300 && input->data.invariant) {
> + if (input->data.location == VARYING_SLOT_FACE) {
> +linker_error(prog,
> + "gl_FrontFacing cannot be declared invariant");
> +return;
> + } else if (!is_gl_position_invariant &&
> +input->data.location == VARYING_SLOT_POS) {
> +linker_error(prog,
> + "gl_FragCoord cannot be declared invariant "
> + "unless gl_Position is also invariant");
> +return;
> + } else if (!is_gl_point_size_invariant &&
> +input->data.location == VARYING_SLOT_PNTC) {
> +linker_error(prog,
> + "gl_PointCoord cannot be declared invariant "
> + "unless gl_PointSize is also invariant");
> +return;
> + }
> +  }
> +
>if (strcmp(input->name, "gl_Color") == 0 && input->data.used) {
>   const ir_variable *const front_color =
>  parameters.get_variable("gl_FrontColor");
> --
> 2.5.5
>
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[Mesa-dev] [PATCH RESEND v4] glsl: enforce invariant conditions for built-in variables

[Lars Hamre]

v2:
 - ES version check (Tapani Pälli)
v3/v4:
 - compare varying slot locations rather than names (Ilia Mirkin)

The conditions for which certain built-in special variables
can be declared invariant were not being checked.

GLSL ES 1.00 specification, Section "Invariance and linkage" says:

For the built-in special variables, gl_FragCoord can
only be declared invariant if and only if gl_Position is
declared invariant. Similarly gl_PointCoord can only be
declared invariant if and only if gl_PointSize is declared
invariant. It is an error to declare gl_FrontFacing as invariant.

This fixes the following piglit tests in spec/glsl-es-1.00/linker:
glsl-fcoord-invariant
glsl-fface-invariant
glsl-pcoord-invariant

Signed-off-by: Lars Hamre 

---

NOTE: Someone with access will need to commit this after the
  review process

 src/compiler/glsl/link_varyings.cpp | 39 +
 1 file changed, 39 insertions(+)

diff --git a/src/compiler/glsl/link_varyings.cpp 
b/src/compiler/glsl/link_varyings.cpp
index 34c8906..755000e 100644
--- a/src/compiler/glsl/link_varyings.cpp
+++ b/src/compiler/glsl/link_varyings.cpp
@@ -336,6 +336,9 @@ cross_validate_outputs_to_inputs(struct gl_shader_program 
*prog,
ir_variable *explicit_locations[MAX_VARYINGS_INCL_PATCH][4] =
   { {NULL, NULL} };

+   bool is_gl_position_invariant = false;
+   bool is_gl_point_size_invariant = false;
+
/* Find all shader outputs in the "producer" stage.
 */
foreach_in_list(ir_instruction, node, producer->ir) {
@@ -344,6 +347,13 @@ cross_validate_outputs_to_inputs(struct gl_shader_program 
*prog,
   if (var == NULL || var->data.mode != ir_var_shader_out)
  continue;

+  if (prog->IsES && prog->Version < 300) {
+ if (var->data.location == VARYING_SLOT_POS)
+is_gl_position_invariant = var->data.invariant;
+ if (var->data.location == VARYING_SLOT_PSIZ)
+is_gl_point_size_invariant = var->data.invariant;
+  }
+
   if (!var->data.explicit_location
   || var->data.location < VARYING_SLOT_VAR0)
  parameters.add_variable(var);
@@ -430,6 +440,35 @@ cross_validate_outputs_to_inputs(struct gl_shader_program 
*prog,
   if (input == NULL || input->data.mode != ir_var_shader_in)
  continue;

+  /*
+   * GLSL ES 1.00 specification, Section "Invariance and linkage" says:
+   *
+   *  "For the built-in special variables, gl_FragCoord can
+   *  only be declared invariant if and only if gl_Position is
+   *  declared invariant. Similarly gl_PointCoord can only be
+   *  declared invariant if and only if gl_PointSize is declared
+   *  invariant. It is an error to declare gl_FrontFacing as invariant."
+   */
+  if (prog->IsES && prog->Version < 300 && input->data.invariant) {
+ if (input->data.location == VARYING_SLOT_FACE) {
+linker_error(prog,
+ "gl_FrontFacing cannot be declared invariant");
+return;
+ } else if (!is_gl_position_invariant &&
+input->data.location == VARYING_SLOT_POS) {
+linker_error(prog,
+ "gl_FragCoord cannot be declared invariant "
+ "unless gl_Position is also invariant");
+return;
+ } else if (!is_gl_point_size_invariant &&
+input->data.location == VARYING_SLOT_PNTC) {
+linker_error(prog,
+ "gl_PointCoord cannot be declared invariant "
+ "unless gl_PointSize is also invariant");
+return;
+ }
+  }
+
   if (strcmp(input->name, "gl_Color") == 0 && input->data.used) {
  const ir_variable *const front_color =
 parameters.get_variable("gl_FrontColor");
--
2.5.5

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