Revert "nir: add late opt to turn inot/b2f combos back to bcsel"

This reverts commit 7acc865226.

With these optimizations in place, the extra constant folding added in
the next commit extends some live ranges of 0.0 and ±1.0 constants, and
that causes several hundred shaders to have more spills and fills.

I believe this optimization we made basically irrelevant by 7725d60938
"intel/fs: Emit better code for b2f(inot(a)) and b2i(inot(a))".

All Gen7.5+ platforms had similar results. (Ice Lake shown)
total instructions in shared programs: 17225303 -> 17224634 (<.01%)
instructions in affected programs: 879402 -> 878733 (-0.08%)
helped: 679
HURT: 1
helped stats (abs) min: 1 max: 1 x̄: 1.00 x̃: 1
helped stats (rel) min: 0.03% max: 0.93% x̄: 0.24% x̃: 0.05%
HURT stats (abs)   min: 10 max: 10 x̄: 10.00 x̃: 10
HURT stats (rel)   min: 0.45% max: 0.45% x̄: 0.45% x̃: 0.45%
95% mean confidence interval for instructions value: -1.02 -0.95
95% mean confidence interval for instructions %-change: -0.26% -0.22%
Instructions are helped.

total cycles in shared programs: 360842595 -> 360828542 (<.01%)
cycles in affected programs: 110443594 -> 110429541 (-0.01%)
helped: 389
HURT: 265
helped stats (abs) min: 1 max: 7525 x̄: 162.81 x̃: 28
helped stats (rel) min: <.01% max: 18.66% x̄: 1.11% x̃: 0.11%
HURT stats (abs)   min: 1 max: 7614 x̄: 185.96 x̃: 48
HURT stats (rel)   min: <.01% max: 25.08% x̄: 0.95% x̃: 0.10%
95% mean confidence interval for cycles value: -75.65 32.67
95% mean confidence interval for cycles %-change: -0.49% -0.06%
Inconclusive result (value mean confidence interval includes 0).

total spills in shared programs: 12159 -> 12161 (0.02%)
spills in affected programs: 13 -> 15 (15.38%)
helped: 0
HURT: 1

total fills in shared programs: 25207 -> 25208 (<.01%)
fills in affected programs: 25 -> 26 (4.00%)
helped: 0
HURT: 1

Ivy Bridge
total instructions in shared programs: 12082019 -> 12082013 (<.01%)
instructions in affected programs: 1033 -> 1027 (-0.58%)
helped: 6
HURT: 0
helped stats (abs) min: 1 max: 1 x̄: 1.00 x̃: 1
helped stats (rel) min: 0.41% max: 0.83% x̄: 0.61% x̃: 0.59%
95% mean confidence interval for instructions value: -1.00 -1.00
95% mean confidence interval for instructions %-change: -0.78% -0.45%
Instructions are helped.

total cycles in shared programs: 179849270 -> 179849157 (<.01%)
cycles in affected programs: 4735 -> 4622 (-2.39%)
helped: 4
HURT: 0
helped stats (abs) min: 2 max: 74 x̄: 28.25 x̃: 18
helped stats (rel) min: 0.13% max: 6.53% x̄: 2.85% x̃: 2.36%
95% mean confidence interval for cycles value: -82.73 26.23
95% mean confidence interval for cycles %-change: -7.98% 2.28%
Inconclusive result (value mean confidence interval includes 0).

Sandy Bridge
total instructions in shared programs: 10882750 -> 10882748 (<.01%)
instructions in affected programs: 266 -> 264 (-0.75%)
helped: 2
HURT: 0

Iron Lake
total cycles in shared programs: 188609440 -> 188609448 (<.01%)
cycles in affected programs: 4320 -> 4328 (0.19%)
helped: 0
HURT: 2

GM45
total cycles in shared programs: 129016868 -> 129016872 (<.01%)
cycles in affected programs: 2302 -> 2306 (0.17%)
helped: 0
HURT: 1

Reviewed-by: Matt Turner <mattst88@gmail.com>

src/compiler/nir/nir_opt_algebraic.py

@@ -1128,9 +1128,6 @@ late_optimizations = [
    (('~flrp@32', ('fadd(is_used_once)', a, b), ('fadd(is_used_once)', a, c), d), ('fadd', ('flrp', b, c, d), a)),
    (('~flrp@64', ('fadd(is_used_once)', a, b), ('fadd(is_used_once)', a, c), d), ('fadd', ('flrp', b, c, d), a)),
 
-   (('b2f(is_used_more_than_once)', ('inot', 'a@1')), ('bcsel', a, 0.0, 1.0)),
-   (('fneg(is_used_more_than_once)', ('b2f', ('inot', 'a@1'))), ('bcsel', a, -0.0, -1.0)),
-
    (('~fadd@32', 1.0, ('fmul(is_used_once)', c , ('fadd', b, -1.0 ))), ('fadd', ('fadd', 1.0, ('fneg', c)), ('fmul', b, c)), 'options->lower_flrp32'),
    (('~fadd@64', 1.0, ('fmul(is_used_once)', c , ('fadd', b, -1.0 ))), ('fadd', ('fadd', 1.0, ('fneg', c)), ('fmul', b, c)), 'options->lower_flrp64'),
 

src/compiler/nir/nir_search_helpers.h

@@ -143,22 +143,6 @@ is_not_const(nir_alu_instr *instr, unsigned src, UNUSED unsigned num_components,
    return !nir_src_is_const(instr->src[src].src);
 }
 
-static inline bool
-is_used_more_than_once(nir_alu_instr *instr)
-{
-   bool zero_if_use = list_empty(&instr->dest.dest.ssa.if_uses);
-   bool zero_use = list_empty(&instr->dest.dest.ssa.uses);
-
-   if (zero_use && zero_if_use)
-      return false;
-   else if (zero_use && list_is_singular(&instr->dest.dest.ssa.if_uses))
-      return false;
-   else if (zero_if_use && list_is_singular(&instr->dest.dest.ssa.uses))
-      return false;
-
-   return true;
-}
-
 static inline bool
 is_used_once(nir_alu_instr *instr)
 {