Mesa (master): nir: Add a flag for lowering fneg/ineg.

[Eric Anholt]

Module: Mesa
Branch: master
Commit: 42a8ace66e539957b31ea96fe9a2aaacdb90f30e
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=42a8ace66e539957b31ea96fe9a2aaacdb90f30e

Author: Eric Anholt <eric at anholt.net>
Date:   Wed Jan 28 10:52:53 2015 -0800

nir: Add a flag for lowering fneg/ineg.

vc4 cse/algebraic-disabled stats:
total instructions in shared programs: 44911 -> 44732 (-0.40%)
instructions in affected programs:     11371 -> 11192 (-1.57%)

v2: Fix broken iabs(isub(0, a)) transformation.
v3: Rebase to master (no TGSI->NIR present)

Reviewed-by: Kenneth Graunke <kenneth at whitecape.org> (v1)

---

 src/glsl/nir/nir.h                |    2 ++
 src/glsl/nir/nir_opt_algebraic.py |   10 ++++++++++
 2 files changed, 12 insertions(+)

diff --git a/src/glsl/nir/nir.h b/src/glsl/nir/nir.h
index 37e15ef..6448d4a 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 f93757e..8d5c03b 100644
--- a/src/glsl/nir/nir_opt_algebraic.py
+++ b/src/glsl/nir/nir_opt_algebraic.py
@@ -141,6 +141,16 @@ optimizations = [
    # next round of opt_algebraic, get picked up by one of the above two.
    (('bcsel', '#a', b, c), ('bcsel', ('ine', 'a', 0), b, c)),
 
+   # 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)), ('iabs', a)),
+
 # This one may not be exact
    (('feq', ('fadd', a, b), 0.0), ('feq', a, ('fneg', b))),
 ]