From 43cc6dbdab76a85ca72d943a125ce90fdf7ccac4 Mon Sep 17 00:00:00 2001
From: Andreas Kloeckner <inform@tiker.net>
Date: Mon, 31 Oct 2011 16:24:19 -0400
Subject: [PATCH] Use straight integer division if isl can show the operands
are nonnegative.
---
MEMO | 6 +++---
loopy/isl_helpers.py | 17 +++++++++++++++++
loopy/symbolic.py | 14 ++++++++++----
3 files changed, 30 insertions(+), 7 deletions(-)
diff --git a/MEMO b/MEMO
index 4b22218b8..6fa8a95c5 100644
--- a/MEMO
+++ b/MEMO
@@ -41,9 +41,6 @@ To-do
- Automatically generate testing code vs. sequential.
-- If isl can prove that all operands are positive, may use '/' instead of
- 'floor_div'.
-
- Fix all tests
- Deal with equality constraints.
@@ -86,6 +83,9 @@ Future ideas
Dealt with
^^^^^^^^^^
+- If isl can prove that all operands are positive, may use '/' instead of
+ 'floor_div'.
+
- For forced workgroup sizes: check that at least one iname
maps to them.
diff --git a/loopy/isl_helpers.py b/loopy/isl_helpers.py
index ba79878e9..d48ca1331 100644
--- a/loopy/isl_helpers.py
+++ b/loopy/isl_helpers.py
@@ -227,4 +227,21 @@ def duplicate_axes(isl_obj, duplicate_inames, new_inames):
+def is_nonnegative(expr, over_set):
+ space = over_set.get_space()
+ from loopy.symbolic import aff_from_expr
+ try:
+ aff = aff_from_expr(space, -expr-1)
+ except:
+ return None
+ expr_neg_set = isl.BasicSet.universe(space).add_constraint(
+ isl.Constraint.inequality_from_aff(aff))
+
+ return over_set.intersect(expr_neg_set).is_empty()
+
+
+
+
+
+
# vim: foldmethod=marker
diff --git a/loopy/symbolic.py b/loopy/symbolic.py
index f41e1b5e3..b25dd2965 100644
--- a/loopy/symbolic.py
+++ b/loopy/symbolic.py
@@ -355,10 +355,16 @@ class LoopyCCodeMapper(CCodeMapper):
raise RuntimeError("nothing known about variable '%s'" % expr.aggregate.name)
def map_floor_div(self, expr, prec):
- if isinstance(expr.denominator, int) and expr.denominator > 0:
- return ("int_floor_div_pos_b(%s, %s)"
- % (self.rec(expr.numerator, PREC_NONE),
- expr.denominator))
+ from loopy.isl_helpers import is_nonnegative
+ num_nonneg = is_nonnegative(expr.numerator, self.kernel.domain)
+ den_nonneg = is_nonnegative(expr.denominator, self.kernel.domain)
+ if den_nonneg:
+ if num_nonneg:
+ return CCodeMapper.map_quotient(self, expr, prec)
+ else:
+ return ("int_floor_div_pos_b(%s, %s)"
+ % (self.rec(expr.numerator, PREC_NONE),
+ expr.denominator))
else:
return ("int_floor_div(%s, %s)"
% (self.rec(expr.numerator, PREC_NONE),
--
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