Mesa (master): nir: bump loop max unroll limit

[Timothy Arceri]

Module: Mesa
Branch: master
Commit: dd65f0efc91418bbafd5cc4b63840b5a734d43d1
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=dd65f0efc91418bbafd5cc4b63840b5a734d43d1

Author: Timothy Arceri <timothy.arceri at collabora.com>
Date:   Wed Jan 18 13:12:37 2017 +1100

nir: bump loop max unroll limit

The original number was chosen in an attempt to match the limits applied to
GLSL IR.

A look at the git history of the why these limits were chosen for GLSL IR
shows it was more to do with the slow speed of unrolling large loops in
GLSL IR than anything else. The speed of loop unrolling in NIR is not a
problem so we may wish to bump this even higher in future.

No shader-db change, however a furture change will disbale the GLSL IR
optimisation loop in the i965 backend results in 4 loops from The Talos
Principle failing to unroll. Bumping the limit allows them to unroll which
results in the instruction count matching the previous output from when the
GLSL IR opts were still enabled.

Reviewed-by: Jason Ekstrand <jason at jlekstrand.net>

---

 src/compiler/nir/nir_opt_loop_unroll.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/compiler/nir/nir_opt_loop_unroll.c b/src/compiler/nir/nir_opt_loop_unroll.c
index 2c19980..37cbced 100644
--- a/src/compiler/nir/nir_opt_loop_unroll.c
+++ b/src/compiler/nir/nir_opt_loop_unroll.c
@@ -460,7 +460,7 @@ is_loop_small_enough_to_unroll(nir_shader *shader, nir_loop_info *li)
       return true;
 
    bool loop_not_too_large =
-      li->num_instructions * li->trip_count <= max_iter * 25;
+      li->num_instructions * li->trip_count <= max_iter * 26;
 
    return loop_not_too_large;
 }