nir/algebraic: Eliminate useless fsat() on operand of comparison w/value in (0, 1)

v2: Fix copy-and-paste bug in a cmp b vs b cmp a cases.

All Gen7+ platforms had similar results. (Ice Lake shown)
total instructions in shared programs: 17224337 -> 17224269 (<.01%)
instructions in affected programs: 13578 -> 13510 (-0.50%)
helped: 68
HURT: 0
helped stats (abs) min: 1 max: 1 x̄: 1.00 x̃: 1
helped stats (rel) min: 0.31% max: 3.12% x̄: 0.84% x̃: 0.42%
95% mean confidence interval for instructions value: -1.00 -1.00
95% mean confidence interval for instructions %-change: -1.05% -0.63%
Instructions are helped.

total cycles in shared programs: 360826090 -> 360825137 (<.01%)
cycles in affected programs: 94867 -> 93914 (-1.00%)
helped: 58
HURT: 1
helped stats (abs) min: 2 max: 28 x̄: 17.74 x̃: 18
helped stats (rel) min: 0.08% max: 3.17% x̄: 1.39% x̃: 1.22%
HURT stats (abs)   min: 76 max: 76 x̄: 76.00 x̃: 76
HURT stats (rel)   min: 2.86% max: 2.86% x̄: 2.86% x̃: 2.86%
95% mean confidence interval for cycles value: -19.53 -12.78
95% mean confidence interval for cycles %-change: -1.56% -1.08%
Cycles are helped.

No changes on any other Intel platform.

Reviewed-by: Matt Turner <[email protected]>
Reviewed-by: Thomas Helland <[email protected]>

1 files changed, 30 insertions, 0 deletions

diff --git a/src/compiler/nir/nir_search_helpers.h b/src/compiler/nir/nir_search_helpers.h
index dd220dfdffd..9e03c610ece 100644
--- a/src/compiler/nir/nir_search_helpers.h
+++ b/src/compiler/nir/nir_search_helpers.h
@@ -109,6 +109,36 @@ is_zero_to_one(nir_alu_instr *instr, unsigned src, unsigned num_components,
    return true;
 }
 
+/**
+ * Exclusive compare with (0, 1).
+ *
+ * This differs from \c is_zero_to_one because that function tests 0 <= src <=
+ * 1 while this function tests 0 < src < 1.
+ */
+static inline bool
+is_gt_0_and_lt_1(nir_alu_instr *instr, unsigned src, unsigned num_components,
+                 const uint8_t *swizzle)
+{
+   /* only constant srcs: */
+   if (!nir_src_is_const(instr->src[src].src))
+      return false;
+
+   for (unsigned i = 0; i < num_components; i++) {
+      switch (nir_op_infos[instr->op].input_types[src]) {
+      case nir_type_float: {
+         double val = nir_src_comp_as_float(instr->src[src].src, swizzle[i]);
+         if (isnan(val) || val <= 0.0f || val >= 1.0f)
+            return false;
+         break;
+      }
+      default:
+         return false;
+      }
+   }
+
+   return true;
+}
+
 static inline bool
 is_not_const_zero(nir_alu_instr *instr, unsigned src, unsigned num_components,
                   const uint8_t *swizzle)