[Mesa-dev] [PATCH v2 2/2] mesa: Add spec citations for DispatchCompute*

[Jordan Justen]

Note: The OpenGL 4.3 - 4.5 specification language for DispatchCompute
appears to have an error regarding the max allowed values. When adding
the specification citation, we note why the code does not match the
specification language.

v2:
 * Updates based on review from Iago

Signed-off-by: Jordan Justen <jordan.l.justen at intel.com>
Cc: Iago Toral Quiroga <itoral at igalia.com>
Cc: Marta Lofstedt <marta.lofstedt at intel.com>
---
 src/mesa/main/api_validate.c | 34 +++++++++++++++++++++++++++++-----
 1 file changed, 29 insertions(+), 5 deletions(-)

diff --git a/src/mesa/main/api_validate.c b/src/mesa/main/api_validate.c
index a3ee8c0..a490189 100644
--- a/src/mesa/main/api_validate.c
+++ b/src/mesa/main/api_validate.c
@@ -918,6 +918,11 @@ check_valid_to_compute(struct gl_context *ctx, const char *function)
       return false;
    }
 
+   /* From the OpenGL 4.3 Core Specification, Chapter 19, Compute Shaders:
+    *
+    * "An INVALID_OPERATION error is generated if there is no active program
+    *  for the compute shader stage."
+    */
    prog = ctx->_Shader->CurrentProgram[MESA_SHADER_COMPUTE];
    if (prog == NULL || prog->_LinkedShaders[MESA_SHADER_COMPUTE] == NULL) {
       _mesa_error(ctx, GL_INVALID_OPERATION,
@@ -940,6 +945,24 @@ _mesa_validate_DispatchCompute(struct gl_context *ctx,
       return GL_FALSE;
 
    for (i = 0; i < 3; i++) {
+      /* From the OpenGL 4.3 Core Specification, Chapter 19, Compute Shaders:
+       *
+       * "An INVALID_VALUE error is generated if any of num_groups_x,
+       *  num_groups_y and num_groups_z are greater than or equal to the
+       *  maximum work group count for the corresponding dimension."
+       *
+       * However, the "or equal to" portions appears to be a specification
+       * bug. In all other areas, the specification appears to indicate that
+       * the number of workgroups can match the MAX_COMPUTE_WORK_GROUP_COUNT
+       * value. For example, under DispatchComputeIndirect:
+       *
+       * "If any of num_groups_x, num_groups_y or num_groups_z is greater than
+       *  the value of MAX_COMPUTE_WORK_GROUP_COUNT for the corresponding
+       *  dimension then the results are undefined."
+       *
+       * Additionally, the OpenGLES 3.1 specification does not contain "or
+       * equal to" as an error condition.
+       */
       if (num_groups[i] > ctx->Const.MaxComputeWorkGroupCount[i]) {
          _mesa_error(ctx, GL_INVALID_VALUE,
                      "glDispatchCompute(num_groups_%c)", 'x' + i);
@@ -977,6 +1000,12 @@ valid_dispatch_indirect(struct gl_context *ctx,
       return GL_FALSE;
    }
 
+   /* From the OpenGL 4.3 Core Specification, Chapter 19, Compute Shaders:
+    *
+    * "An INVALID_OPERATION error is generated if no buffer is bound to the
+    *  DRAW_INDIRECT_BUFFER binding, or if the command would source data
+    *  beyond the end of the buffer object."
+    */
    if (!_mesa_is_bufferobj(ctx->DispatchIndirectBuffer)) {
       _mesa_error(ctx, GL_INVALID_OPERATION,
                   "%s: no buffer bound to DISPATCH_INDIRECT_BUFFER", name);
@@ -989,11 +1018,6 @@ valid_dispatch_indirect(struct gl_context *ctx,
       return GL_FALSE;
    }
 
-   /* From the ARB_compute_shader specification:
-    *
-    * "An INVALID_OPERATION error is generated if this command sources data
-    *  beyond the end of the buffer object [...]"
-    */
    if (ctx->DispatchIndirectBuffer->Size < end) {
       _mesa_error(ctx, GL_INVALID_OPERATION,
                   "%s(DISPATCH_INDIRECT_BUFFER too small)", name);
-- 
2.6.2