[Mesa-dev] [PATCH 5/9] nir: Add a flag for lowering fneg/ineg.

[Eric Anholt]

vc4 cse/algebraic-disabled stats:
total instructions in shared programs: 44911 -> 44732 (-0.40%)
instructions in affected programs:     11371 -> 11192 (-1.57%)
---
 src/gallium/drivers/vc4/vc4_program.c |  1 +
 src/glsl/nir/nir.h                    |  2 ++
 src/glsl/nir/nir_opt_algebraic.py     | 10 ++++++++++
 3 files changed, 13 insertions(+)

diff --git a/src/gallium/drivers/vc4/vc4_program.c 
b/src/gallium/drivers/vc4/vc4_program.c
index fd818b4..304cd04 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_fpow = true,
         .lower_fsqrt = true,
+        .lower_negate = true,
 };
 
 static struct vc4_compile *
diff --git a/src/glsl/nir/nir.h b/src/glsl/nir/nir.h
index b0ad4b0..0746adf 100644
--- a/src/glsl/nir/nir.h
+++ b/src/glsl/nir/nir.h
@@ -1329,6 +1329,8 @@ typedef struct nir_function {
 typedef struct nir_shader_compiler_options {
    bool lower_fpow;
    bool lower_fsqrt;
+   /** lowers fneg and ineg to fsub and isub. */
+   bool lower_negate;
 } nir_shader_compiler_options;
 
 typedef struct nir_shader {
diff --git a/src/glsl/nir/nir_opt_algebraic.py 
b/src/glsl/nir/nir_opt_algebraic.py
index 2020997..7d5f543 100644
--- a/src/glsl/nir/nir_opt_algebraic.py
+++ b/src/glsl/nir/nir_opt_algebraic.py
@@ -136,6 +136,16 @@ optimizations = [
    (('bcsel', a, b, b), b),
    (('fcsel', a, b, b), b),
 
+   # Subtracts
+   (('fsub', 0.0, ('fsub', 0.0, a)), a),
+   (('isub', 0, ('isub', 0, a)), a),
+   (('fneg', a), ('fsub', 0.0, a), 'options->lower_negate'),
+   (('ineg', a), ('isub', 0, a), 'options->lower_negate'),
+   (('fadd', a, ('fsub', 0.0, b)), ('fsub', a, b)),
+   (('iadd', a, ('isub', 0, b)), ('isub', a, b)),
+   (('fabs', ('fsub', 0.0, a)), ('fabs', a)),
+   (('iabs', ('isub', 0, a)), ('fabs', a)),
+
 # This one may not be exact
    (('feq', ('fadd', a, b), 0.0), ('feq', a, ('fneg', b))),
 ]
-- 
2.1.4

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