From 4c44c6245cf0234a9af5e1cf971d2a26b40e4243 Mon Sep 17 00:00:00 2001
From: Sven Verdoolaege <skimo@kotnet.org>
Date: Mon, 5 Oct 2009 12:22:56 +0200
Subject: isl_tab_pip.c: detect equalities in gbr context on each parametric
 cut

A new div that was introduced to express a parametric cut may,
within the current context, be an affine combination of other divs.
If so, we want to find these equalities as soon as possible
as this may allow us to more easily determine feasibility of
a constraint.
---
 isl_tab_pip.c | 47 ++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 46 insertions(+), 1 deletion(-)

(limited to 'isl_tab_pip.c')

diff --git a/isl_tab_pip.c b/isl_tab_pip.c
index 003197e5..3f96fc15 100644
--- a/isl_tab_pip.c
+++ b/isl_tab_pip.c
@@ -74,6 +74,8 @@ struct isl_context_op {
 	/* add div "div" to context and return index and non-negativity */
 	int (*add_div)(struct isl_context *context, struct isl_vec *div,
 			int *nonneg);
+	int (*detect_equalities)(struct isl_context *context,
+			struct isl_tab *tab);
 	/* return row index of "best" split */
 	int (*best_split)(struct isl_context *context, struct isl_tab *tab);
 	/* check if context has already been determined to be empty */
@@ -1537,6 +1539,7 @@ static int add_parametric_cut(struct isl_tab *tab, int row,
 	int r;
 	isl_int *r_row;
 	int col;
+	int n;
 	unsigned off = 2 + tab->M;
 
 	if (!context)
@@ -1546,6 +1549,7 @@ static int add_parametric_cut(struct isl_tab *tab, int row,
 	if (!div)
 		return -1;
 
+	n = tab->n_div;
 	d = context->op->get_div(context, tab, div);
 	if (d < 0)
 		return -1;
@@ -1613,7 +1617,12 @@ static int add_parametric_cut(struct isl_tab *tab, int row,
 
 	isl_vec_free(div);
 
-	return tab->con[r].index;
+	row = tab->con[r].index;
+
+	if (d >= n && context->op->detect_equalities(context, tab) < 0)
+		return -1;
+
+	return row;
 }
 
 /* Construct a tableau for bmap that can be used for computing
@@ -1924,6 +1933,12 @@ static int context_lex_add_div(struct isl_context *context, struct isl_vec *div,
 	return context_tab_add_div(clex->tab, div, nonneg);
 }
 
+static int context_lex_detect_equalities(struct isl_context *context,
+		struct isl_tab *tab)
+{
+	return 0;
+}
+
 static int context_lex_best_split(struct isl_context *context,
 		struct isl_tab *tab)
 {
@@ -2078,6 +2093,7 @@ struct isl_context_op isl_context_lex_op = {
 	context_lex_test_ineq,
 	context_lex_get_div,
 	context_lex_add_div,
+	context_lex_detect_equalities,
 	context_lex_best_split,
 	context_lex_is_empty,
 	context_lex_is_ok,
@@ -2415,6 +2431,34 @@ static int context_gbr_test_ineq(struct isl_context *context, isl_int *ineq)
 	return feasible;
 }
 
+static int context_gbr_detect_equalities(struct isl_context *context,
+	struct isl_tab *tab)
+{
+	struct isl_context_gbr *cgbr = (struct isl_context_gbr *)context;
+	struct isl_ctx *ctx;
+	struct isl_tab *tab_cone;
+	int i;
+	enum isl_lp_result res;
+
+	ctx = cgbr->tab->mat->ctx;
+
+	tab_cone = isl_tab_from_recession_cone(cgbr->tab->bset);
+	if (!tab_cone)
+		goto error;
+	tab_cone->bset = isl_basic_set_dup(cgbr->tab->bset);
+	tab_cone = isl_tab_detect_implicit_equalities(tab_cone);
+
+	cgbr->tab = isl_tab_detect_equalities(cgbr->tab, tab_cone);
+
+	isl_tab_free(tab_cone);
+
+	return 0;
+error:
+	isl_tab_free(cgbr->tab);
+	cgbr->tab = NULL;
+	return -1;
+}
+
 static int context_gbr_get_div(struct isl_context *context, struct isl_tab *tab,
 		struct isl_vec *div)
 {
@@ -2525,6 +2569,7 @@ struct isl_context_op isl_context_gbr_op = {
 	context_gbr_test_ineq,
 	context_gbr_get_div,
 	context_gbr_add_div,
+	context_gbr_detect_equalities,
 	context_gbr_best_split,
 	context_gbr_is_empty,
 	context_gbr_is_ok,
-- 
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