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authorKenneth Graunke <kenneth@whitecape.org>2016-10-14 17:59:36 -0700
committerEmil Velikov <emil.l.velikov@gmail.com>2016-12-14 19:03:11 +0000
commit41c18889be9844213b989705781f56865b82117d (patch)
treea7e2d9493ec898e4657a2eab9bafd2052ba4b4c0 /src
parentadda8b9eb67a888c10da1e9beb9426dffce74744 (diff)
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i965: Allocate at least some URB space even when max_vertices = 0.
Allocating zero URB space is a really bad idea. The hardware has to give threads a handle to their URB space, and threads have to use that to terminate the thread. Having it be an empty region just breaks a lot of assumptions. Hence, why we asserted that it isn't possible. Unfortunately, it /is/ possible prior to Gen8, if max_vertices = 0. In theory a geometry shader could do SSBO/image access and maybe still accomplish something. In reality, this is tripped up by conformance tests. Gen8+ already avoids this problem by placing the vertex count DWord in the URB entry header. This fixes things on earlier generations. Cc: mesa-stable@lists.freedesktop.org Signed-off-by: Kenneth Graunke <kenneth@whitecape.org> Reviewed-by: Anuj Phogat <anuj.phogat@gmail.com> Tested-by: Ian Romanick <ian.d.romanick@intel.com> (cherry picked from commit a41f5dcb141a11ca5ca0c765c305027b0f0b609e)
Diffstat (limited to 'src')
-rw-r--r--src/mesa/drivers/dri/i965/brw_vec4_gs_visitor.cpp8
1 files changed, 7 insertions, 1 deletions
diff --git a/src/mesa/drivers/dri/i965/brw_vec4_gs_visitor.cpp b/src/mesa/drivers/dri/i965/brw_vec4_gs_visitor.cpp
index b0ee289..ac200d2 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4_gs_visitor.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4_gs_visitor.cpp
@@ -780,7 +780,13 @@ brw_compile_gs(const struct brw_compiler *compiler, void *log_data,
if (compiler->devinfo->gen >= 8)
output_size_bytes += 32;
- assert(output_size_bytes >= 1);
+ /* Shaders can technically set max_vertices = 0, at which point we
+ * may have a URB size of 0 bytes. Nothing good can come from that,
+ * so enforce a minimum size.
+ */
+ if (output_size_bytes == 0)
+ output_size_bytes = 1;
+
unsigned max_output_size_bytes = GEN7_MAX_GS_URB_ENTRY_SIZE_BYTES;
if (compiler->devinfo->gen == 6)
max_output_size_bytes = GEN6_MAX_GS_URB_ENTRY_SIZE_BYTES;