diff options
author | Ian Romanick <[email protected]> | 2018-06-13 12:32:27 -0700 |
---|---|---|
committer | Ian Romanick <[email protected]> | 2018-06-15 17:22:27 -0700 |
commit | 284b563fb0689f8c51aae45ad9e331ba4b776ddf (patch) | |
tree | 88275eaeec03e56dc42da2cffd831756f4a22dbf /src/intel | |
parent | 4106f6ce54f77c3cb5712eafc1358f53b99b5e09 (diff) |
i965/fs: Optimize OR with 0 into a MOV
fs_visitor::set_gs_stream_control_data_bits generates some code like
"control_data_bits | stream_id << ((2 * (vertex_count - 1)) % 32)" as
part of EmitVertex. The first time this (dynamically) occurs in the
shader, control_data_bits is zero. Many times we can determine this
statically and various optimizations will collaborate to make one of the
OR operands literal zero.
Converting the OR to a MOV usually allows it to be copy-propagated away.
However, this does not happen in at least some shaders (in the assembly
output of shaders/closed/UnrealEngine4/EffectsCaveDemo/301.shader_test,
search for shl).
All of the affected shaders are geometry shaders.
Broadwell and Skylake had similar results. (Skylake shown)
total instructions in shared programs: 14375452 -> 14375413 (<.01%)
instructions in affected programs: 6422 -> 6383 (-0.61%)
helped: 39
HURT: 0
helped stats (abs) min: 1 max: 1 x̄: 1.00 x̃: 1
helped stats (rel) min: 0.14% max: 2.56% x̄: 1.91% x̃: 2.56%
95% mean confidence interval for instructions value: -1.00 -1.00
95% mean confidence interval for instructions %-change: -2.26% -1.57%
Instructions are helped.
total cycles in shared programs: 531981179 -> 531980555 (<.01%)
cycles in affected programs: 27493 -> 26869 (-2.27%)
helped: 39
HURT: 0
helped stats (abs) min: 16 max: 16 x̄: 16.00 x̃: 16
helped stats (rel) min: 0.60% max: 7.92% x̄: 5.94% x̃: 7.92%
95% mean confidence interval for cycles value: -16.00 -16.00
95% mean confidence interval for cycles %-change: -6.98% -4.90%
Cycles are helped.
No changes on earlier platforms.
Signed-off-by: Ian Romanick <[email protected]>
Diffstat (limited to 'src/intel')
-rw-r--r-- | src/intel/compiler/brw_fs.cpp | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/src/intel/compiler/brw_fs.cpp b/src/intel/compiler/brw_fs.cpp index d67c0a41922..d836b268629 100644 --- a/src/intel/compiler/brw_fs.cpp +++ b/src/intel/compiler/brw_fs.cpp @@ -2448,7 +2448,8 @@ fs_visitor::opt_algebraic() } break; case BRW_OPCODE_OR: - if (inst->src[0].equals(inst->src[1])) { + if (inst->src[0].equals(inst->src[1]) || + inst->src[1].is_zero()) { inst->opcode = BRW_OPCODE_MOV; inst->src[1] = reg_undef; progress = true; |