nir: add iabs-lowering code
Microsoft's DXIL is based on LLVM, which doesn't have an integer ABS
opcode, but instead needs it lowered to NEG + MAX. We need to do this
with an option, to prevent an already existing optimization rule from
undoing this.
Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5211>
diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
index 005f762..aa7ff44 100644
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -3042,6 +3042,9 @@
/** enables rules to lower fsign to fsub and flt */
bool lower_fsign;
+ /** enables rules to lower iabs to ineg+imax */
+ bool lower_iabs;
+
/* lower fdph to fdot4 */
bool lower_fdph;
diff --git a/src/compiler/nir/nir_opt_algebraic.py b/src/compiler/nir/nir_opt_algebraic.py
index 65cff5c..4a2efa8 100644
--- a/src/compiler/nir/nir_opt_algebraic.py
+++ b/src/compiler/nir/nir_opt_algebraic.py
@@ -543,7 +543,7 @@
(('fmax', a, ('fabs', a)), ('fabs', a)),
(('imax', a, ('iabs', a)), ('iabs', a)),
(('fmax', a, ('fneg', a)), ('fabs', a)),
- (('imax', a, ('ineg', a)), ('iabs', a)),
+ (('imax', a, ('ineg', a)), ('iabs', a), '!options->lower_iabs'),
(('~fmax', ('fabs', a), 0.0), ('fabs', a)),
(('fmin', ('fmax', a, 0.0), 1.0), ('fsat', a), '!options->lower_fsat'),
# fmax(fmin(a, 1.0), 0.0) is inexact because it returns 1.0 on NaN, while
@@ -1902,6 +1902,7 @@
(('iadd', 'a', ('ineg', 'b')), ('isub', 'a', 'b'), '!options->lower_sub'),
(('fneg', a), ('fsub', 0.0, a), 'options->lower_negate'),
(('ineg', a), ('isub', 0, a), 'options->lower_negate'),
+ (('iabs', a), ('imax', a, ('ineg', a)), 'options->lower_iabs'),
# These are duplicated from the main optimizations table. The late
# patterns that rearrange expressions like x - .5 < 0 to x < .5 can create
