[Mesa-dev] [PATCH] glsl: Make bitfield_insert/extract and bfi/bfm non-vectorizable.

[Kenneth Graunke]

Currently, opt_vectorize() tries to combine:

    result.x = bitfieldInsert(src0.x, src1.x, src2.x, src3.x);
    result.y = bitfieldInsert(src0.y, src1.y, src2.y, src3.y);
    result.z = bitfieldInsert(src0.z, src1.z, src2.z, src3.z);
    result.w = bitfieldInsert(src0.w, src1.w, src2.w, src3.w);

into a single ir_quadop_bitfield_insert opcode, which operates on
ivec4s.  However, GLSL IR's opcodes currently require the bits and
offset parameters to be scalar integers.  So, this breaks.

We want to be able to vectorize this eventually, but for now, just
chicken out and make opt_vectorize() bail by marking all the bitfield
insert/extract related opcodes as horizontal.  This is a relatively
uncommon case today, so we'll do the simple fix for stable branches,
and fix it properly on master.

Fixes assertion failures when compiling Shadow of Mordor vertex shaders
on i965 in vec4 mode (where OptimizeForAOS enables opt_vectorize()).

Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
Cc: mesa-stable at lists.freedesktop.org
Cc: Matt Turner <mattst88 at gmail.com>
Cc: Jason Ekstrand <jason at jlekstrand.net>
Cc: Ilia Mirkin <imirkin at alum.mit.edu>
---
 src/glsl/ir.h | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

I found some issues with my previous patch, and am working on a more
complete set.  In the meantime, this fixes the issue.

diff --git a/src/glsl/ir.h b/src/glsl/ir.h
index a728c03..93e0734 100644
--- a/src/glsl/ir.h
+++ b/src/glsl/ir.h
@@ -1726,7 +1726,12 @@ public:
              operation == ir_binop_dot ||
              operation == ir_binop_vector_extract ||
              operation == ir_triop_vector_insert ||
-             operation == ir_quadop_vector;
+             operation == ir_quadop_vector ||
+             /* TODO: these can't currently be vectorized */
+             operation == ir_quadop_bitfield_insert ||
+             operation == ir_triop_bitfield_extract ||
+             operation == ir_triop_bfi ||
+             operation == ir_binop_bfm;
    }
 
    /**
-- 
2.7.0