nir/algebraic: Flag inexact optimizations

Many of our optimizations, while great for cutting shaders down to size,
aren't really precision-safe.  This commit tries to flag all of the
inexact floating-point optimizations so they don't get run on values that
are flagged "exact".  It's a bit conservative and maybe flags some safe
optimizations as unsafe but that's better than missing one.

Reviewed-by: Francisco Jerez <currojerez@riseup.net>

1 files changed, 62 insertions, 59 deletions

diff --git a/src/compiler/nir/nir_opt_algebraic.py b/src/compiler/nir/nir_opt_algebraic.py
index 7e3aa5a..5363323 100644
--- a/src/compiler/nir/nir_opt_algebraic.py
+++ b/src/compiler/nir/nir_opt_algebraic.py
@@ -61,19 +61,19 @@ optimizations = [
    (('fabs', ('fneg', a)), ('fabs', a)),
    (('iabs', ('iabs', a)), ('iabs', a)),
    (('iabs', ('ineg', a)), ('iabs', a)),
-   (('fadd', a, 0.0), a),
+   (('~fadd', a, 0.0), a),
    (('iadd', a, 0), a),
    (('usadd_4x8', a, 0), a),
    (('usadd_4x8', a, ~0), ~0),
-   (('fadd', ('fmul', a, b), ('fmul', a, c)), ('fmul', a, ('fadd', b, c))),
+   (('~fadd', ('fmul', a, b), ('fmul', a, c)), ('fmul', a, ('fadd', b, c))),
    (('iadd', ('imul', a, b), ('imul', a, c)), ('imul', a, ('iadd', b, c))),
-   (('fadd', ('fneg', a), a), 0.0),
+   (('~fadd', ('fneg', a), a), 0.0),
    (('iadd', ('ineg', a), a), 0),
    (('iadd', ('ineg', a), ('iadd', a, b)), b),
    (('iadd', a, ('iadd', ('ineg', a), b)), b),
-   (('fadd', ('fneg', a), ('fadd', a, b)), b),
-   (('fadd', a, ('fadd', ('fneg', a), b)), b),
-   (('fmul', a, 0.0), 0.0),
+   (('~fadd', ('fneg', a), ('fadd', a, b)), b),
+   (('~fadd', a, ('fadd', ('fneg', a), b)), b),
+   (('~fmul', a, 0.0), 0.0),
    (('imul', a, 0), 0),
    (('umul_unorm_4x8', a, 0), 0),
    (('umul_unorm_4x8', a, ~0), a),
@@ -81,29 +81,29 @@ optimizations = [
    (('imul', a, 1), a),
    (('fmul', a, -1.0), ('fneg', a)),
    (('imul', a, -1), ('ineg', a)),
-   (('ffma', 0.0, a, b), b),
-   (('ffma', a, 0.0, b), b),
-   (('ffma', a, b, 0.0), ('fmul', a, b)),
+   (('~ffma', 0.0, a, b), b),
+   (('~ffma', a, 0.0, b), b),
+   (('~ffma', a, b, 0.0), ('fmul', a, b)),
    (('ffma', a, 1.0, b), ('fadd', a, b)),
    (('ffma', 1.0, a, b), ('fadd', a, b)),
-   (('flrp', a, b, 0.0), a),
-   (('flrp', a, b, 1.0), b),
-   (('flrp', a, a, b), a),
-   (('flrp', 0.0, a, b), ('fmul', a, b)),
-   (('flrp', a, b, ('b2f', c)), ('bcsel', c, b, a), 'options->lower_flrp'),
+   (('~flrp', a, b, 0.0), a),
+   (('~flrp', a, b, 1.0), b),
+   (('~flrp', a, a, b), a),
+   (('~flrp', 0.0, a, b), ('fmul', a, b)),
+   (('~flrp', a, b, ('b2f', c)), ('bcsel', c, b, a), 'options->lower_flrp'),
    (('flrp', a, b, c), ('fadd', ('fmul', c, ('fsub', b, a)), a), 'options->lower_flrp'),
    (('ffract', a), ('fsub', a, ('ffloor', a)), 'options->lower_ffract'),
-   (('fadd', ('fmul', a, ('fadd', 1.0, ('fneg', ('b2f', c)))), ('fmul', b, ('b2f', c))), ('bcsel', c, b, a), 'options->lower_flrp'),
-   (('fadd', ('fmul', a, ('fadd', 1.0, ('fneg',         c ))), ('fmul', b,         c )), ('flrp', a, b, c), '!options->lower_flrp'),
-   (('fadd', a, ('fmul', ('b2f', c), ('fadd', b, ('fneg', a)))), ('bcsel', c, b, a), 'options->lower_flrp'),
-   (('fadd', a, ('fmul',         c , ('fadd', b, ('fneg', a)))), ('flrp', a, b, c), '!options->lower_flrp'),
+   (('~fadd', ('fmul', a, ('fadd', 1.0, ('fneg', ('b2f', c)))), ('fmul', b, ('b2f', c))), ('bcsel', c, b, a), 'options->lower_flrp'),
+   (('~fadd', ('fmul', a, ('fadd', 1.0, ('fneg',         c ))), ('fmul', b,         c )), ('flrp', a, b, c), '!options->lower_flrp'),
+   (('~fadd', a, ('fmul', ('b2f', c), ('fadd', b, ('fneg', a)))), ('bcsel', c, b, a), 'options->lower_flrp'),
+   (('~fadd', a, ('fmul',         c , ('fadd', b, ('fneg', a)))), ('flrp', a, b, c), '!options->lower_flrp'),
    (('ffma', a, b, c), ('fadd', ('fmul', a, b), c), 'options->lower_ffma'),
-   (('fadd', ('fmul', a, b), c), ('ffma', a, b, c), '!options->lower_ffma'),
+   (('~fadd', ('fmul', a, b), c), ('ffma', a, b, c), '!options->lower_ffma'),
    # Comparison simplifications
-   (('inot', ('flt', a, b)), ('fge', a, b)),
-   (('inot', ('fge', a, b)), ('flt', a, b)),
-   (('inot', ('feq', a, b)), ('fne', a, b)),
-   (('inot', ('fne', a, b)), ('feq', a, b)),
+   (('~inot', ('flt', a, b)), ('fge', a, b)),
+   (('~inot', ('fge', a, b)), ('flt', a, b)),
+   (('~inot', ('feq', a, b)), ('fne', a, b)),
+   (('~inot', ('fne', a, b)), ('feq', a, b)),
    (('inot', ('ilt', a, b)), ('ige', a, b)),
    (('inot', ('ige', a, b)), ('ilt', a, b)),
    (('inot', ('ieq', a, b)), ('ine', a, b)),
@@ -132,15 +132,15 @@ optimizations = [
    (('imax', a, a), a),
    (('umin', a, a), a),
    (('umax', a, a), a),
-   (('fmin', ('fmax', a, 0.0), 1.0), ('fsat', a), '!options->lower_fsat'),
-   (('fmax', ('fmin', a, 1.0), 0.0), ('fsat', a), '!options->lower_fsat'),
+   (('~fmin', ('fmax', a, 0.0), 1.0), ('fsat', a), '!options->lower_fsat'),
+   (('~fmax', ('fmin', a, 1.0), 0.0), ('fsat', a), '!options->lower_fsat'),
    (('fsat', a), ('fmin', ('fmax', a, 0.0), 1.0), 'options->lower_fsat'),
    (('fsat', ('fsat', a)), ('fsat', a)),
    (('fmin', ('fmax', ('fmin', ('fmax', a, 0.0), 1.0), 0.0), 1.0), ('fmin', ('fmax', a, 0.0), 1.0)),
-   (('ior', ('flt', a, b), ('flt', a, c)), ('flt', a, ('fmax', b, c))),
-   (('ior', ('flt', a, c), ('flt', b, c)), ('flt', ('fmin', a, b), c)),
-   (('ior', ('fge', a, b), ('fge', a, c)), ('fge', a, ('fmin', b, c))),
-   (('ior', ('fge', a, c), ('fge', b, c)), ('fge', ('fmax', a, b), c)),
+   (('~ior', ('flt', a, b), ('flt', a, c)), ('flt', a, ('fmax', b, c))),
+   (('~ior', ('flt', a, c), ('flt', b, c)), ('flt', ('fmin', a, b), c)),
+   (('~ior', ('fge', a, b), ('fge', a, c)), ('fge', a, ('fmin', b, c))),
+   (('~ior', ('fge', a, c), ('fge', b, c)), ('fge', ('fmax', a, b), c)),
    (('fabs', ('slt', a, b)), ('slt', a, b)),
    (('fabs', ('sge', a, b)), ('sge', a, b)),
    (('fabs', ('seq', a, b)), ('seq', a, b)),
@@ -191,35 +191,35 @@ optimizations = [
    (('iand', 0xff, ('ushr', a, 24)), ('ushr', a, 24)),
    (('iand', 0xffff, ('ushr', a, 16)), ('ushr', a, 16)),
    # Exponential/logarithmic identities
-   (('fexp2', ('flog2', a)), a), # 2^lg2(a) = a
-   (('flog2', ('fexp2', a)), a), # lg2(2^a) = a
+   (('~fexp2', ('flog2', a)), a), # 2^lg2(a) = a
+   (('~flog2', ('fexp2', a)), a), # lg2(2^a) = a
    (('fpow', a, b), ('fexp2', ('fmul', ('flog2', a), b)), 'options->lower_fpow'), # a^b = 2^(lg2(a)*b)
-   (('fexp2', ('fmul', ('flog2', a), b)), ('fpow', a, b), '!options->lower_fpow'), # 2^(lg2(a)*b) = a^b
-   (('fexp2', ('fadd', ('fmul', ('flog2', a), b), ('fmul', ('flog2', c), d))),
-    ('fmul', ('fpow', a, b), ('fpow', c, d)), '!options->lower_fpow'), # 2^(lg2(a) * b + lg2(c) + d) = a^b * c^d
-   (('fpow', a, 1.0), a),
-   (('fpow', a, 2.0), ('fmul', a, a)),
-   (('fpow', a, 4.0), ('fmul', ('fmul', a, a), ('fmul', a, a))),
-   (('fpow', 2.0, a), ('fexp2', a)),
-   (('fpow', ('fpow', a, 2.2), 0.454545), a),
-   (('fpow', ('fabs', ('fpow', a, 2.2)), 0.454545), ('fabs', a)),
-   (('fsqrt', ('fexp2', a)), ('fexp2', ('fmul', 0.5, a))),
-   (('frcp', ('fexp2', a)), ('fexp2', ('fneg', a))),
-   (('frsq', ('fexp2', a)), ('fexp2', ('fmul', -0.5, a))),
-   (('flog2', ('fsqrt', a)), ('fmul', 0.5, ('flog2', a))),
-   (('flog2', ('frcp', a)), ('fneg', ('flog2', a))),
-   (('flog2', ('frsq', a)), ('fmul', -0.5, ('flog2', a))),
-   (('flog2', ('fpow', a, b)), ('fmul', b, ('flog2', a))),
-   (('fadd', ('flog2', a), ('flog2', b)), ('flog2', ('fmul', a, b))),
-   (('fadd', ('flog2', a), ('fneg', ('flog2', b))), ('flog2', ('fdiv', a, b))),
-   (('fmul', ('fexp2', a), ('fexp2', b)), ('fexp2', ('fadd', a, b))),
+   (('~fexp2', ('fmul', ('flog2', a), b)), ('fpow', a, b), '!options->lower_fpow'), # 2^(lg2(a)*b) = a^b
+   (('~fexp2', ('fadd', ('fmul', ('flog2', a), b), ('fmul', ('flog2', c), d))),
+    ('~fmul', ('fpow', a, b), ('fpow', c, d)), '!options->lower_fpow'), # 2^(lg2(a) * b + lg2(c) + d) = a^b * c^d
+   (('~fpow', a, 1.0), a),
+   (('~fpow', a, 2.0), ('fmul', a, a)),
+   (('~fpow', a, 4.0), ('fmul', ('fmul', a, a), ('fmul', a, a))),
+   (('~fpow', 2.0, a), ('fexp2', a)),
+   (('~fpow', ('fpow', a, 2.2), 0.454545), a),
+   (('~fpow', ('fabs', ('fpow', a, 2.2)), 0.454545), ('fabs', a)),
+   (('~fsqrt', ('fexp2', a)), ('fexp2', ('fmul', 0.5, a))),
+   (('~frcp', ('fexp2', a)), ('fexp2', ('fneg', a))),
+   (('~frsq', ('fexp2', a)), ('fexp2', ('fmul', -0.5, a))),
+   (('~flog2', ('fsqrt', a)), ('fmul', 0.5, ('flog2', a))),
+   (('~flog2', ('frcp', a)), ('fneg', ('flog2', a))),
+   (('~flog2', ('frsq', a)), ('fmul', -0.5, ('flog2', a))),
+   (('~flog2', ('fpow', a, b)), ('fmul', b, ('flog2', a))),
+   (('~fadd', ('flog2', a), ('flog2', b)), ('flog2', ('fmul', a, b))),
+   (('~fadd', ('flog2', a), ('fneg', ('flog2', b))), ('flog2', ('fdiv', a, b))),
+   (('~fmul', ('fexp2', a), ('fexp2', b)), ('fexp2', ('fadd', a, b))),
    # Division and reciprocal
-   (('fdiv', 1.0, a), ('frcp', a)),
+   (('~fdiv', 1.0, a), ('frcp', a)),
    (('fdiv', a, b), ('fmul', a, ('frcp', b)), 'options->lower_fdiv'),
-   (('frcp', ('frcp', a)), a),
-   (('frcp', ('fsqrt', a)), ('frsq', a)),
+   (('~frcp', ('frcp', a)), a),
+   (('~frcp', ('fsqrt', a)), ('frsq', a)),
    (('fsqrt', a), ('frcp', ('frsq', a)), 'options->lower_fsqrt'),
-   (('frcp', ('frsq', a)), ('fsqrt', a), '!options->lower_fsqrt'),
+   (('~frcp', ('frsq', a)), ('fsqrt', a), '!options->lower_fsqrt'),
    # Boolean simplifications
    (('ieq', 'a@bool', True), a),
    (('ine', 'a@bool', True), ('inot', a)),
@@ -256,7 +256,7 @@ optimizations = [
    (('iand', 0xffff, a), ('extract_u16', a, 0), '!options->lower_extract_word'),
 
    # Subtracts
-   (('fsub', a, ('fsub', 0.0, b)), ('fadd', a, b)),
+   (('~fsub', a, ('fsub', 0.0, b)), ('fadd', a, b)),
    (('isub', a, ('isub', 0, b)), ('iadd', a, b)),
    (('ussub_4x8', a, 0), a),
    (('ussub_4x8', a, ~0), 0),
@@ -264,7 +264,7 @@ optimizations = [
    (('isub', a, b), ('iadd', a, ('ineg', b)), 'options->lower_sub'),
    (('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)),
+   (('~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)),
@@ -393,10 +393,13 @@ for op in ['flt', 'fge', 'feq', 'fne',
 # they help code generation but do not necessarily produce code that is
 # more easily optimizable.
 late_optimizations = [
+   # Most of these optimizations aren't quite safe when you get infinity or
+   # Nan involved but the first one should be fine.
    (('flt', ('fadd', a, b), 0.0), ('flt', a, ('fneg', b))),
-   (('fge', ('fadd', a, b), 0.0), ('fge', a, ('fneg', b))),
-   (('feq', ('fadd', a, b), 0.0), ('feq', a, ('fneg', b))),
-   (('fne', ('fadd', a, b), 0.0), ('fne', a, ('fneg', b))),
+   (('~fge', ('fadd', a, b), 0.0), ('fge', a, ('fneg', b))),
+   (('~feq', ('fadd', a, b), 0.0), ('feq', a, ('fneg', b))),
+   (('~fne', ('fadd', a, b), 0.0), ('fne', a, ('fneg', b))),
+
    (('fdot2', a, b), ('fdot_replicated2', a, b), 'options->fdot_replicates'),
    (('fdot3', a, b), ('fdot_replicated3', a, b), 'options->fdot_replicates'),
    (('fdot4', a, b), ('fdot_replicated4', a, b), 'options->fdot_replicates'),