[Mesa-dev] [PATCH 8/9] nir: Add a flag for lowering fsat.

[Eric Anholt]

vc4 cse/algebraic-disabled stats:
total instructions in shared programs: 44356 -> 44354 (-0.00%)
instructions in affected programs:     55 -> 53 (-3.64%)
---
 src/gallium/drivers/vc4/vc4_program.c | 1 +
 src/glsl/nir/nir.h                    | 1 +
 src/glsl/nir/nir_opt_algebraic.py     | 3 ++-
 3 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/gallium/drivers/vc4/vc4_program.c b/src/gallium/drivers/vc4/vc4_program.c
index 8be2d15..3f06005 100644
--- a/src/gallium/drivers/vc4/vc4_program.c
+++ b/src/gallium/drivers/vc4/vc4_program.c
@@ -2100,6 +2100,7 @@ nir_to_qir(struct vc4_compile *c)
 static const nir_shader_compiler_options nir_options = {
         .lower_ffma = true,
         .lower_fpow = true,
+        .lower_fsat = true,
         .lower_fsqrt = true,
         .lower_negate = true,
 };
diff --git a/src/glsl/nir/nir.h b/src/glsl/nir/nir.h
index f7f5d33..03be7b4 100644
--- a/src/glsl/nir/nir.h
+++ b/src/glsl/nir/nir.h
@@ -1329,6 +1329,7 @@ typedef struct nir_function {
 typedef struct nir_shader_compiler_options {
    bool lower_ffma;
    bool lower_fpow;
+   bool lower_fsat;
    bool lower_fsqrt;
    /** lowers fneg and ineg to fsub and isub. */
    bool lower_negate;
diff --git a/src/glsl/nir/nir_opt_algebraic.py b/src/glsl/nir/nir_opt_algebraic.py
index 84c60ec..9542ef3 100644
--- a/src/glsl/nir/nir_opt_algebraic.py
+++ b/src/glsl/nir/nir_opt_algebraic.py
@@ -83,7 +83,8 @@ optimizations = [
    (('feq', ('fadd', a, b), 0.0), ('feq', a, ('fneg', b))),
    (('fne', ('fadd', a, b), 0.0), ('fne', a, ('fneg', b))),
    (('fge', ('fneg', ('fabs', a)), 0.0), ('feq', a, 0.0)),
-   (('fmin', ('fmax', a, 0.0), 1.0), ('fsat', a)),
+   (('fmin', ('fmax', a, 0.0), 1.0), ('fsat', a), '!options->lower_fsat'),
+   (('fsat', a), ('fmin', ('fmax', a, 0.0), 1.0), 'options->lower_fsat'),
    # Logical and bit operations
    (('fand', a, 0.0), 0.0),
    (('iand', a, a), a),
-- 
2.1.4