From f831bbb4a09ce90a470eb703c40adf12ea8acbda Mon Sep 17 00:00:00 2001
From: Andreas Kloeckner <inform@tiker.net>
Date: Sun, 3 May 2015 23:57:04 -0500
Subject: [PATCH] Allow tweaking constant-preference heuristic in
 static_*_of_pw-aff, specifically for for loop bounds

---
 loopy/codegen/loop.py |  4 ++--
 loopy/isl_helpers.py  | 39 ++++++++++++++++++++++++++-------------
 2 files changed, 28 insertions(+), 15 deletions(-)

diff --git a/loopy/codegen/loop.py b/loopy/codegen/loop.py
index f27458fec..dcea94690 100644
--- a/loopy/codegen/loop.py
+++ b/loopy/codegen/loop.py
@@ -320,11 +320,11 @@ def generate_sequential_loop_dim_code(kernel, sched_index, codegen_state):
         static_lbound = static_min_of_pw_aff(
                 kernel.cache_manager.dim_min(
                     dom_and_slab, loop_iname_idx).coalesce(),
-                constants_only=False)
+                constants_only=False, prefer_constants=False)
         static_ubound = static_max_of_pw_aff(
                 kernel.cache_manager.dim_max(
                     dom_and_slab, loop_iname_idx).coalesce(),
-                constants_only=False)
+                constants_only=False, prefer_constants=False)
 
         # }}}
 
diff --git a/loopy/isl_helpers.py b/loopy/isl_helpers.py
index fdf38b768..53e6309c7 100644
--- a/loopy/isl_helpers.py
+++ b/loopy/isl_helpers.py
@@ -137,7 +137,8 @@ def iname_rel_aff(space, iname, rel, aff):
         raise ValueError("unknown value of 'rel': %s" % rel)
 
 
-def static_extremum_of_pw_aff(pw_aff, constants_only, set_method, what, context):
+def static_extremum_of_pw_aff(pw_aff, constants_only, set_method, what, context,
+        prefer_constants):
     if context is not None:
         context = isl.align_spaces(context, pw_aff.get_domain_space(),
                 obj_bigger_ok=True).params()
@@ -163,12 +164,21 @@ def static_extremum_of_pw_aff(pw_aff, constants_only, set_method, what, context)
 
     # put constant bounds with unbounded validity first
     # FIXME: Heuristi-hack.
-    order = [
-            (True, False),  # constant, unbounded validity
-            (False, False),  # nonconstant, unbounded validity
-            (True, True),  # constant, bounded validity
-            (False, True),  # nonconstant, bounded validity
-            ]
+    if prefer_constants:
+        order = [
+                (True, False),  # constant, unbounded validity
+                (False, False),  # nonconstant, unbounded validity
+                (True, True),  # constant, bounded validity
+                (False, True),  # nonconstant, bounded validity
+                ]
+    else:
+        order = [
+                (False, False),  # nonconstant, unbounded validity
+                (True, False),  # constant, unbounded validity
+                (False, True),  # nonconstant, bounded validity
+                (True, True),  # constant, bounded validity
+                ]
+
     pieces = flatten([
             [(set, aff) for set, aff in pieces
                 if aff.is_cst() == want_is_constant
@@ -199,19 +209,22 @@ def static_extremum_of_pw_aff(pw_aff, constants_only, set_method, what, context)
             % (what, pw_aff))
 
 
-def static_min_of_pw_aff(pw_aff, constants_only, context=None):
+def static_min_of_pw_aff(pw_aff, constants_only, context=None,
+        prefer_constants=True):
     return static_extremum_of_pw_aff(pw_aff, constants_only, isl.PwAff.ge_set,
-            "minimum", context)
+            "minimum", context, prefer_constants)
 
 
-def static_max_of_pw_aff(pw_aff, constants_only, context=None):
+def static_max_of_pw_aff(pw_aff, constants_only, context=None,
+        prefer_constants=True):
     return static_extremum_of_pw_aff(pw_aff, constants_only, isl.PwAff.le_set,
-            "maximum", context)
+            "maximum", context, prefer_constants)
 
 
-def static_value_of_pw_aff(pw_aff, constants_only, context=None):
+def static_value_of_pw_aff(pw_aff, constants_only, context=None,
+        prefer_constants=True):
     return static_extremum_of_pw_aff(pw_aff, constants_only, isl.PwAff.eq_set,
-            "value", context)
+            "value", context, prefer_constants)
 
 
 def duplicate_axes(isl_obj, duplicate_inames, new_inames):
-- 
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