intel/fs: Do cmod prop again after scheduling

Pre-RA scheduling can create more opportunities for CMOD propagation.
This takes advantage of that.

It may be worth doing this again in post-RA scheduling, but there are
additional problems there.

I'm a little torn about the use of the OPT() macro.  On the one hand, it
would be confusing to see dumps from INTEL_DEBUG=optimizer that don't
match the final output.  On the other hand, since register allocation
can fail, the same pass can be run multiple times.  Each time one or
both passes might or might not make progress.  This would also lead to
incongruous, confusing output.

Ice Lake
total instructions in shared programs: 14549808 -> 14548529 (<.01%)
instructions in affected programs: 231985 -> 230706 (-0.55%)
helped: 632
HURT: 0
helped stats (abs) min: 1 max: 32 x̄: 2.02 x̃: 1
helped stats (rel) min: 0.05% max: 2.56% x̄: 0.57% x̃: 0.41%
95% mean confidence interval for instructions value: -2.25 -1.79
95% mean confidence interval for instructions %-change: -0.61% -0.54%
Instructions are helped.

total cycles in shared programs: 203770850 -> 203776599 (<.01%)
cycles in affected programs: 2495653 -> 2501402 (0.23%)
helped: 282
HURT: 197
helped stats (abs) min: 1 max: 242 x̄: 20.37 x̃: 16
helped stats (rel) min: <.01% max: 11.65% x̄: 0.91% x̃: 0.64%
HURT stats (abs)   min: 2 max: 609 x̄: 58.35 x̃: 20
HURT stats (rel)   min: <.01% max: 10.97% x̄: 1.35% x̃: 0.66%
95% mean confidence interval for cycles value: 5.27 18.73
95% mean confidence interval for cycles %-change: -0.16% 0.21%
Inconclusive result (%-change mean confidence interval includes 0).

LOST:   0
GAINED: 2

Skylake
total instructions in shared programs: 13447708 -> 13446594 (<.01%)
instructions in affected programs: 216813 -> 215699 (-0.51%)
helped: 623
HURT: 0
helped stats (abs) min: 1 max: 32 x̄: 1.79 x̃: 1
helped stats (rel) min: 0.06% max: 2.86% x̄: 0.59% x̃: 0.42%
95% mean confidence interval for instructions value: -1.99 -1.59
95% mean confidence interval for instructions %-change: -0.63% -0.55%
Instructions are helped.

total cycles in shared programs: 193759224 -> 193762726 (<.01%)
cycles in affected programs: 2540035 -> 2543537 (0.14%)
helped: 249
HURT: 190
helped stats (abs) min: 2 max: 196 x̄: 16.67 x̃: 14
helped stats (rel) min: <.01% max: 4.71% x̄: 0.66% x̃: 0.62%
HURT stats (abs)   min: 2 max: 614 x̄: 40.27 x̃: 14
HURT stats (rel)   min: 0.02% max: 5.78% x̄: 0.86% x̃: 0.37%
95% mean confidence interval for cycles value: 2.57 13.39
95% mean confidence interval for cycles %-change: -0.11% 0.11%
Inconclusive result (%-change mean confidence interval includes 0).

LOST:   0
GAINED: 1

Broadwell
total instructions in shared programs: 13418631 -> 13417393 (<.01%)
instructions in affected programs: 243192 -> 241954 (-0.51%)
helped: 694
HURT: 0
helped stats (abs) min: 1 max: 31 x̄: 1.78 x̃: 1
helped stats (rel) min: 0.06% max: 2.86% x̄: 0.59% x̃: 0.44%
95% mean confidence interval for instructions value: -1.95 -1.62
95% mean confidence interval for instructions %-change: -0.62% -0.55%
Instructions are helped.

total cycles in shared programs: 200822940 -> 200829128 (<.01%)
cycles in affected programs: 2128651 -> 2134839 (0.29%)
helped: 251
HURT: 226
helped stats (abs) min: 1 max: 200 x̄: 14.32 x̃: 12
helped stats (rel) min: <.01% max: 3.56% x̄: 0.60% x̃: 0.50%
HURT stats (abs)   min: 2 max: 611 x̄: 43.28 x̃: 18
HURT stats (rel)   min: 0.02% max: 7.03% x̄: 0.93% x̃: 0.54%
95% mean confidence interval for cycles value: 7.44 18.50
95% mean confidence interval for cycles %-change: 0.02% 0.23%
Cycles are HURT.

Haswell and Ivy Bridge had similar results. (Haswell shown)
total instructions in shared programs: 11569710 -> 11568829 (<.01%)
instructions in affected programs: 147862 -> 146981 (-0.60%)
helped: 487
HURT: 0
helped stats (abs) min: 1 max: 34 x̄: 1.81 x̃: 1
helped stats (rel) min: 0.12% max: 4.75% x̄: 0.57% x̃: 0.45%
95% mean confidence interval for instructions value: -2.03 -1.59
95% mean confidence interval for instructions %-change: -0.61% -0.54%
Instructions are helped.

total cycles in shared programs: 187079425 -> 187079437 (<.01%)
cycles in affected programs: 1088494 -> 1088506 (<.01%)
helped: 234
HURT: 124
helped stats (abs) min: 2 max: 282 x̄: 22.66 x̃: 16
helped stats (rel) min: 0.03% max: 7.88% x̄: 0.93% x̃: 0.75%
HURT stats (abs)   min: 1 max: 276 x̄: 42.86 x̃: 20
HURT stats (rel)   min: 0.03% max: 6.70% x̄: 0.99% x̃: 0.53%
95% mean confidence interval for cycles value: -5.54 5.61
95% mean confidence interval for cycles %-change: -0.41% -0.11%
Inconclusive result (value mean confidence interval includes 0).

total spills in shared programs: 7746 -> 7740 (-0.08%)
spills in affected programs: 6 -> 0
helped: 1
HURT: 0

total fills in shared programs: 6264 -> 6258 (-0.10%)
fills in affected programs: 6 -> 0
helped: 1
HURT: 0

Sandy Bridge
total instructions in shared programs: 10688576 -> 10688177 (<.01%)
instructions in affected programs: 137875 -> 137476 (-0.29%)
helped: 358
HURT: 0
helped stats (abs) min: 1 max: 9 x̄: 1.11 x̃: 1
helped stats (rel) min: 0.15% max: 1.43% x̄: 0.35% x̃: 0.28%
95% mean confidence interval for instructions value: -1.18 -1.05
95% mean confidence interval for instructions %-change: -0.37% -0.32%
Instructions are helped.

total cycles in shared programs: 153397144 -> 153393046 (<.01%)
cycles in affected programs: 1220713 -> 1216615 (-0.34%)
helped: 255
HURT: 31
helped stats (abs) min: 1 max: 304 x̄: 16.71 x̃: 16
helped stats (rel) min: <.01% max: 6.70% x̄: 0.41% x̃: 0.31%
HURT stats (abs)   min: 1 max: 41 x̄: 5.29 x̃: 3
HURT stats (rel)   min: 0.02% max: 0.65% x̄: 0.16% x̃: 0.11%
95% mean confidence interval for cycles value: -17.44 -11.22
95% mean confidence interval for cycles %-change: -0.40% -0.29%
Cycles are helped.

Iron Lake
total instructions in shared programs: 8106894 -> 8105529 (-0.02%)
instructions in affected programs: 287197 -> 285832 (-0.48%)
helped: 1099
HURT: 0
helped stats (abs) min: 1 max: 10 x̄: 1.24 x̃: 1
helped stats (rel) min: 0.16% max: 4.55% x̄: 0.67% x̃: 0.61%
95% mean confidence interval for instructions value: -1.29 -1.19
95% mean confidence interval for instructions %-change: -0.70% -0.64%
Instructions are helped.

total cycles in shared programs: 188347022 -> 188344266 (<.01%)
cycles in affected programs: 3740632 -> 3737876 (-0.07%)
helped: 758
HURT: 10
helped stats (abs) min: 2 max: 38 x̄: 3.68 x̃: 2
helped stats (rel) min: <.01% max: 1.00% x̄: 0.12% x̃: 0.08%
HURT stats (abs)   min: 2 max: 4 x̄: 3.20 x̃: 4
HURT stats (rel)   min: 0.03% max: 0.07% x̄: 0.06% x̃: 0.07%
95% mean confidence interval for cycles value: -3.82 -3.35
95% mean confidence interval for cycles %-change: -0.13% -0.11%
Cycles are helped.

GM45
total instructions in shared programs: 4985449 -> 4984768 (-0.01%)
instructions in affected programs: 145154 -> 144473 (-0.47%)
helped: 547
HURT: 0
helped stats (abs) min: 1 max: 10 x̄: 1.24 x̃: 1
helped stats (rel) min: 0.16% max: 2.86% x̄: 0.66% x̃: 0.61%
95% mean confidence interval for instructions value: -1.31 -1.18
95% mean confidence interval for instructions %-change: -0.69% -0.62%
Instructions are helped.

total cycles in shared programs: 128835062 -> 128833144 (<.01%)
cycles in affected programs: 2720650 -> 2718732 (-0.07%)
helped: 517
HURT: 1
helped stats (abs) min: 2 max: 38 x̄: 3.71 x̃: 2
helped stats (rel) min: <.01% max: 0.89% x̄: 0.11% x̃: 0.07%
HURT stats (abs)   min: 2 max: 2 x̄: 2.00 x̃: 2
HURT stats (rel)   min: 0.04% max: 0.04% x̄: 0.04% x̃: 0.04%
95% mean confidence interval for cycles value: -4.02 -3.39
95% mean confidence interval for cycles %-change: -0.12% -0.10%
Cycles are helped.

Reviewed-by: Matt Turner <[email protected]>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/3965>

1 files changed, 11 insertions, 0 deletions

diff --git a/src/intel/compiler/brw_fs.cpp b/src/intel/compiler/brw_fs.cpp
index 749c69718a4..f284a2b6644 100644
--- a/src/intel/compiler/brw_fs.cpp
+++ b/src/intel/compiler/brw_fs.cpp
@@ -7803,6 +7803,17 @@ fs_visitor::allocate_registers(unsigned min_dispatch_width, bool allow_spilling)
          break;
       }
 
+      /* Scheduling may create additional opportunities for CMOD propagation,
+       * so let's do it again.  If CMOD propagation made any progress,
+       * elminate dead code one more time.
+       */
+      bool progress = false;
+      const int iteration = 99;
+      int pass_num = 0;
+
+      if (OPT(opt_cmod_propagation))
+         OPT(dead_code_eliminate);
+
       /* We only allow spilling for the last schedule mode and only if the
        * allow_spilling parameter and dispatch width work out ok.
        */