intel/fs: Generate if instructions with inverted conditions

Per-platform results were all over the place, so I have included all the
results here.  There is an important note at the bottom of the commit
message.

Skylake
total instructions in shared programs: 15184683 -> 15184679 (<.01%)
instructions in affected programs: 2786 -> 2782 (-0.14%)
helped: 4
HURT: 0
helped stats (abs) min: 1 max: 1 x̄: 1.00 x̃: 1
helped stats (rel) min: 0.05% max: 0.84% x̄: 0.44% x̃: 0.44%
95% mean confidence interval for instructions value: -1.00 -1.00
95% mean confidence interval for instructions %-change: -0.96% 0.07%
Inconclusive result (%-change mean confidence interval includes 0).

total cycles in shared programs: 370961367 -> 370961173 (<.01%)
cycles in affected programs: 205867 -> 205673 (-0.09%)
helped: 5
HURT: 1
helped stats (abs) min: 1 max: 149 x̄: 39.60 x̃: 16
helped stats (rel) min: 0.02% max: 1.05% x̄: 0.45% x̃: 0.55%
HURT stats (abs)   min: 4 max: 4 x̄: 4.00 x̃: 4
HURT stats (rel)   min: 0.03% max: 0.03% x̄: 0.03% x̃: 0.03%
95% mean confidence interval for cycles value: -93.01 28.34
95% mean confidence interval for cycles %-change: -0.82% 0.08%
Inconclusive result (value mean confidence interval includes 0).

Broadwell
total instructions in shared programs: 15465366 -> 15465362 (<.01%)
instructions in affected programs: 2799 -> 2795 (-0.14%)
helped: 4
HURT: 0
helped stats (abs) min: 1 max: 1 x̄: 1.00 x̃: 1
helped stats (rel) min: 0.04% max: 0.84% x̄: 0.44% x̃: 0.44%
95% mean confidence interval for instructions value: -1.00 -1.00
95% mean confidence interval for instructions %-change: -0.96% 0.07%
Inconclusive result (%-change mean confidence interval includes 0).

total cycles in shared programs: 410938419 -> 410938531 (<.01%)
cycles in affected programs: 566028 -> 566140 (0.02%)
helped: 18
HURT: 17
helped stats (abs) min: 1 max: 16 x̄: 3.50 x̃: 1
helped stats (rel) min: <.01% max: 1.05% x̄: 0.13% x̃: <.01%
HURT stats (abs)   min: 1 max: 12 x̄: 10.29 x̃: 12
HURT stats (rel)   min: <.01% max: 0.16% x̄: 0.08% x̃: 0.09%
95% mean confidence interval for cycles value: 0.31 6.09
95% mean confidence interval for cycles %-change: -0.10% 0.05%
Inconclusive result (%-change mean confidence interval includes 0).

Haswell
total instructions in shared programs: 13749760 -> 13749759 (<.01%)
instructions in affected programs: 2241 -> 2240 (-0.04%)
helped: 1
HURT: 0

total cycles in shared programs: 385398913 -> 385398363 (<.01%)
cycles in affected programs: 554914 -> 554364 (-0.10%)
helped: 31
HURT: 1
helped stats (abs) min: 1 max: 453 x̄: 18.00 x̃: 6
helped stats (rel) min: <.01% max: 0.25% x̄: 0.03% x̃: 0.05%
HURT stats (abs)   min: 8 max: 8 x̄: 8.00 x̃: 8
HURT stats (rel)   min: 0.06% max: 0.06% x̄: 0.06% x̃: 0.06%
95% mean confidence interval for cycles value: -45.88 11.51
95% mean confidence interval for cycles %-change: -0.05% -0.02%
Inconclusive result (value mean confidence interval includes 0).

Ivy Bridge
total cycles in shared programs: 180663626 -> 180663881 (<.01%)
cycles in affected programs: 472350 -> 472605 (0.05%)
helped: 15
HURT: 30
helped stats (abs) min: 1 max: 1 x̄: 1.00 x̃: 1
helped stats (rel) min: <.01% max: <.01% x̄: <.01% x̃: <.01%
HURT stats (abs)   min: 8 max: 10 x̄: 9.00 x̃: 9
HURT stats (rel)   min: 0.06% max: 0.14% x̄: 0.10% x̃: 0.10%
95% mean confidence interval for cycles value: 4.21 7.12
95% mean confidence interval for cycles %-change: 0.05% 0.08%
Cycles are HURT.

Sandy Bridge
total cycles in shared programs: 154568664 -> 154569225 (<.01%)
cycles in affected programs: 356486 -> 357047 (0.16%)
helped: 1
HURT: 31
helped stats (abs) min: 2 max: 2 x̄: 2.00 x̃: 2
helped stats (rel) min: 0.02% max: 0.02% x̄: 0.02% x̃: 0.02%
HURT stats (abs)   min: 4 max: 33 x̄: 18.16 x̃: 8
HURT stats (rel)   min: 0.05% max: 0.23% x̄: 0.14% x̃: 0.10%
95% mean confidence interval for cycles value: 12.19 22.87
95% mean confidence interval for cycles %-change: 0.10% 0.16%
Cycles are HURT.

Iron Lake
total instructions in shared programs: 8206589 -> 8206565 (<.01%)
instructions in affected programs: 3024 -> 3000 (-0.79%)
helped: 12
HURT: 0
helped stats (abs) min: 2 max: 2 x̄: 2.00 x̃: 2
helped stats (rel) min: 0.75% max: 0.83% x̄: 0.80% x̃: 0.80%
95% mean confidence interval for instructions value: -2.00 -2.00
95% mean confidence interval for instructions %-change: -0.82% -0.77%
Instructions are helped.

total cycles in shared programs: 187657428 -> 187656228 (<.01%)
cycles in affected programs: 95748 -> 94548 (-1.25%)
helped: 12
HURT: 0
helped stats (abs) min: 80 max: 120 x̄: 100.00 x̃: 100
helped stats (rel) min: 1.00% max: 1.66% x̄: 1.27% x̃: 1.21%
95% mean confidence interval for cycles value: -113.27 -86.73
95% mean confidence interval for cycles %-change: -1.43% -1.11%
Cycles are helped.

GM45
total instructions in shared programs: 5037569 -> 5037557 (<.01%)
instructions in affected programs: 1521 -> 1509 (-0.79%)
helped: 6
HURT: 0
helped stats (abs) min: 2 max: 2 x̄: 2.00 x̃: 2
helped stats (rel) min: 0.75% max: 0.83% x̄: 0.79% x̃: 0.79%
95% mean confidence interval for instructions value: -2.00 -2.00
95% mean confidence interval for instructions %-change: -0.83% -0.75%
Instructions are helped.

total cycles in shared programs: 128101478 -> 128100758 (<.01%)
cycles in affected programs: 52746 -> 52026 (-1.37%)
helped: 6
HURT: 0
helped stats (abs) min: 120 max: 120 x̄: 120.00 x̃: 120
helped stats (rel) min: 1.16% max: 1.66% x̄: 1.41% x̃: 1.41%
95% mean confidence interval for cycles value: -120.00 -120.00
95% mean confidence interval for cycles %-change: -1.70% -1.12%
Cycles are helped.

This change has almost no effect right now.  However, removing this
patch (but leaving the patch "nir/algebraic: Replace a bcsel of a b2f
with a b2f(!(a || b))") after adding a patch that removes !(a < b) -> (a
>= b) optimizations (like
https://patchwork.freedesktop.org/patch/264787/) has the following
results on Skylake:

Skylake
total instructions in shared programs: 15071022 -> 15089710 (0.12%)
instructions in affected programs: 1022219 -> 1040907 (1.83%)
helped: 1
HURT: 3937
helped stats (abs) min: 41 max: 41 x̄: 41.00 x̃: 41
helped stats (rel) min: 1.01% max: 1.01% x̄: 1.01% x̃: 1.01%
HURT stats (abs)   min: 1 max: 256 x̄: 4.76 x̃: 4
HURT stats (rel)   min: 0.05% max: 11.18% x̄: 2.59% x̃: 2.60%
95% mean confidence interval for instructions value: 4.56 4.93
95% mean confidence interval for instructions %-change: 2.54% 2.64%
Instructions are HURT.

total cycles in shared programs: 369777134 -> 370092923 (0.09%)
cycles in affected programs: 17516573 -> 17832362 (1.80%)
helped: 115
HURT: 3624
helped stats (abs) min: 1 max: 1721 x̄: 81.18 x̃: 28
helped stats (rel) min: <.01% max: 10.74% x̄: 1.24% x̃: 0.65%
HURT stats (abs)   min: 1 max: 12640 x̄: 89.71 x̃: 54
HURT stats (rel)   min: <.01% max: 28.24% x̄: 4.72% x̃: 4.52%
95% mean confidence interval for cycles value: 75.21 93.71
95% mean confidence interval for cycles %-change: 4.43% 4.64%
Cycles are HURT.

total spills in shared programs: 9450 -> 9442 (-0.08%)
spills in affected programs: 166 -> 158 (-4.82%)
helped: 2
HURT: 0

total fills in shared programs: 21115 -> 21094 (-0.10%)
fills in affected programs: 438 -> 417 (-4.79%)
helped: 2
HURT: 0

LOST:   1
GAINED: 0

Reviewed-by: Kenneth Graunke <[email protected]>

1 files changed, 20 insertions, 3 deletions

diff --git a/src/intel/compiler/brw_fs_nir.cpp b/src/intel/compiler/brw_fs_nir.cpp
index 9ecfad99939..fb373e1757e 100644
--- a/src/intel/compiler/brw_fs_nir.cpp
+++ b/src/intel/compiler/brw_fs_nir.cpp
@@ -381,13 +381,30 @@ fs_visitor::nir_emit_cf_list(exec_list *list)
 void
 fs_visitor::nir_emit_if(nir_if *if_stmt)
 {
+   bool invert;
+   fs_reg cond_reg;
+
+   /* If the condition has the form !other_condition, use other_condition as
+    * the source, but invert the predicate on the if instruction.
+    */
+   nir_alu_instr *const cond = nir_src_as_alu_instr(&if_stmt->condition);
+   if (cond != NULL && cond->op == nir_op_inot) {
+      assert(!cond->src[0].negate);
+      assert(!cond->src[0].abs);
+
+      invert = true;
+      cond_reg = get_nir_src(cond->src[0].src);
+   } else {
+      invert = false;
+      cond_reg = get_nir_src(if_stmt->condition);
+   }
+
    /* first, put the condition into f0 */
    fs_inst *inst = bld.MOV(bld.null_reg_d(),
-                            retype(get_nir_src(if_stmt->condition),
-                                   BRW_REGISTER_TYPE_D));
+                           retype(cond_reg, BRW_REGISTER_TYPE_D));
    inst->conditional_mod = BRW_CONDITIONAL_NZ;
 
-   bld.IF(BRW_PREDICATE_NORMAL);
+   bld.IF(BRW_PREDICATE_NORMAL)->predicate_inverse = invert;
 
    nir_emit_cf_list(&if_stmt->then_list);