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i965/fs: Fix the example about overwriting uniforms in SIMD16.

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mov takes only a single source argument. Example instruction
inexplicably changed from add to mov in commit f10f5e49.

Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
This commit is contained in:
Matt Turner
2013-12-07 12:59:59 -08:00
parent 71bc11a375
commit 80b949f16b
1 changed files with 5 additions and 5 deletions
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src/mesa/drivers/dri/i965/brw_fs_live_variables.cpp
+5 -5
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@@ -64,18 +64,18 @@ fs_live_variables::setup_one_read(bblock_t *block, fs_inst *inst,
* destination starts (naturally). This gets more complicated for
* simd16, because the instruction:
*
* mov(16) g4<1>F g4<8,8,1>F g6<8,8,1>F
* add(16) g4<1>F g4<8,8,1>F g6<8,8,1>F
*
* is actually decoded in hardware as:
*
* mov(8) g4<1>F g4<8,8,1>F g6<8,8,1>F
* mov(8) g5<1>F g5<8,8,1>F g7<8,8,1>F
* add(8) g4<1>F g4<8,8,1>F g6<8,8,1>F
* add(8) g5<1>F g5<8,8,1>F g7<8,8,1>F
*
* Which is safe. However, if we have uniform accesses
* happening, we get into trouble:
*
* mov(8) g4<1>F g4<0,1,0>F g6<8,8,1>F
* mov(8) g5<1>F g4<0,1,0>F g7<8,8,1>F
* add(8) g4<1>F g4<0,1,0>F g6<8,8,1>F
* add(8) g5<1>F g4<0,1,0>F g7<8,8,1>F
*
* Now our destination for the first instruction overwrote the
* second instruction's src0, and we get garbage for those 8