commit d47cb4124ac9d515bd91fa3c1e807ac1c05bda35
author Nanley Chery <nanley.g.chery@intel.com> Mon Nov 02 09:02:42 2020 -0800
committer Dylan Baker <dylan.c.baker@intel.com> Tue Nov 17 10:57:31 2020 -0800
tree dad9660221ace9406c80864fca69472fe0089884
parent 5b83eb0b0980a5f488ef4bab589f8537960f7072

mesa: Clamp some depth values in glClearBufferfv

OpenGL 3.0 spec, section 4.2.3 "Clearing the Buffers":

   If buffer is DEPTH, drawbuffer must be zero, and value points to the
   single depth value to clear the depth buffer to. Clamping and type
   conversion for fixed-point depth buffers are performed in the same
   fashion as for ClearDepth.

Enables iris to pass the clearbuffer-depth piglit test.

v2. Add spec citation. (Eric Anholt)
v3. Don't clamp floating point formats. (Eric Anholt)

Cc: mesa-stable
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7410>
(cherry picked from commit 1bf539b3a2129779addde397886870c00045e6d7)

.pick_status.json

diff --git a/.pick_status.json b/.pick_status.json
index db02c68..ad51376 100644
--- a/.pick_status.json
+++ b/.pick_status.json
@@ -1093,7 +1093,7 @@
         "description": "mesa: Clamp some depth values in glClearBufferfv",
         "nominated": true,
         "nomination_type": 0,
-        "resolution": 0,
+        "resolution": 1,
         "master_sha": null,
         "because_sha": null
     },

src/mesa/main/clear.c

diff --git a/src/mesa/main/clear.c b/src/mesa/main/clear.c
index ca0ecd9..0a51a86 100644
--- a/src/mesa/main/clear.c
+++ b/src/mesa/main/clear.c
@@ -30,6 +30,7 @@
 
 
 
+#include "glformats.h"
 #include "glheader.h"
 #include "clear.h"
 #include "context.h"
@@ -589,7 +590,20 @@
           * hook instead.
           */
          const GLclampd clearSave = ctx->Depth.Clear;
-         ctx->Depth.Clear = *value;
+
+         /* Page 263 (page 279 of the PDF) of the OpenGL 3.0 spec says:
+          *
+          *     "If buffer is DEPTH, drawbuffer must be zero, and value points
+          *     to the single depth value to clear the depth buffer to.
+          *     Clamping and type conversion for fixed-point depth buffers are
+          *     performed in the same fashion as for ClearDepth."
+          */
+         const struct gl_renderbuffer *rb =
+            ctx->DrawBuffer->Attachment[BUFFER_DEPTH].Renderbuffer;
+         const bool is_float_depth =
+            _mesa_has_depth_float_channel(rb->InternalFormat);
+         ctx->Depth.Clear = is_float_depth ? *value : SATURATE(*value);
+
          ctx->Driver.Clear(ctx, BUFFER_BIT_DEPTH);
          ctx->Depth.Clear = clearSave;
       }