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i965: make BRW_COMPRESSION_2NDHALF valid for brw_SAMPLE

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SIMD8 sampler messages are allowed in SIMD16 mode, and they could not work
without BRW_COMPRESSION_2NDHALF.  Later PRMs (gen5 and later) do not
explicitly state whether BRW_COMPRESSION_2NDHALF is allowed, but they do have
examples using send with SecHalf.  It should be safe to assume SecHalf is
valid.

Signed-off-by: Chia-I Wu <olv@lunarg.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
This commit is contained in:
Chia-I Wu
2013-09-27 15:23:56 +08:00
committed by Chia-I Wu
parent 1176a3aac6
commit 44f0777f17
1 changed files with 16 additions and 1 deletions
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src/mesa/drivers/dri/i965/brw_eu_emit.c
+16 -1
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@@ -2197,7 +2197,22 @@ void brw_SAMPLE(struct brw_compile *p,
insn = next_insn(p, BRW_OPCODE_SEND);
insn->header.predicate_control = 0; /* XXX */
insn->header.compression_control = BRW_COMPRESSION_NONE;
/* From the 965 PRM (volume 4, part 1, section 14.2.41):
*
* "Instruction compression is not allowed for this instruction (that
* is, send). The hardware behavior is undefined if this instruction is
* set as compressed. However, compress control can be set to "SecHalf"
* to affect the EMask generation."
*
* No similar wording is found in later PRMs, but there are examples
* utilizing send with SecHalf. More importantly, SIMD8 sampler messages
* are allowed in SIMD16 mode and they could not work without SecHalf. For
* these reasons, we allow BRW_COMPRESSION_2NDHALF here.
*/
if (insn->header.compression_control != BRW_COMPRESSION_2NDHALF)
insn->header.compression_control = BRW_COMPRESSION_NONE;
if (brw->gen < 6)
insn->header.destreg__conditionalmod = msg_reg_nr;