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i965: disable loop unrolling in GLSL IR 

There is a single regression in loop unrolling which is:

loops HURT:   shaders/orbital_explorer.shader_test GS SIMD8:    0 -> 1

However the loop is huge so it seems reasonable not to unroll it. It's
surprising that GLSL IR does unroll it.

shader-db results BDW:

total instructions in shared programs: 13037455 -> 13036947 (-0.00%)
instructions in affected programs: 17982 -> 17474 (-2.83%)
helped: 63
HURT: 25

total cycles in shared programs: 262217870 -> 262227990 (0.00%)
cycles in affected programs: 2287046 -> 2297166 (0.44%)
helped: 969
HURT: 844

total loops in shared programs: 2951 -> 2952 (0.03%)
loops in affected programs: 0 -> 1
helped: 0
HURT: 1

LOST:   0
GAINED: 1

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
This commit is contained in:
Timothy Arceri 2016-12-13 11:37:25 +11:00
parent 715f0d06d1
commit 40e9f2f138
1 changed files with 1 additions and 1 deletions
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2
src/mesa/drivers/dri/i965/brw_compiler.c
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@ -122,7 +122,7 @@ brw_compiler_create(void *mem_ctx, const struct gen_device_info *devinfo)
/* We want the GLSL compiler to emit code that uses condition codes */
for (int i = 0; i < MESA_SHADER_STAGES; i++) {
compiler->glsl_compiler_options[i].MaxUnrollIterations = 32;
compiler->glsl_compiler_options[i].MaxUnrollIterations = 0;
compiler->glsl_compiler_options[i].MaxIfDepth =
devinfo->gen < 6 ? 16 : UINT_MAX;