From: Roger Sayle <roger@eyesopen.com>
Date: Sat, 26 Nov 2005 04:06:57 +0000 (+0000)
Subject: re PR middle-end/21309 (internal compiler error: in expand_mult_const, at expmed... 
X-Git-Tag: releases/gcc-4.2.0~5742
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=18eaea7f15cf89aa5e0c9c99c76b14dfc39563c5;p=thirdparty%2Fgcc.git

re PR middle-end/21309 (internal compiler error: in expand_mult_const, at expmed.c:2884)


	PR middle-end/21309
	* expmed.c (choose_mult_variant): Return immediately when mult_cost
	is less than zero.  Limit mult_cost to a reasonable upper bound for
	the synthetic multiplication sequence.

From-SVN: r107537
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 654acf22846a..c4ec10c521f7 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2005-11-25  Roger Sayle  <roger@eyesopen.com>
+
+	PR middle-end/21309
+	* expmed.c (choose_mult_variant): Return immediately when mult_cost
+	is less than zero.  Limit mult_cost to a reasonable upper bound for
+	the synthetic multiplication sequence.
+
 2005-11-25  Kaveh R. Ghazi  <ghazi@caip.rutgers.edu>
 
 	PR middle-end/25022
diff --git a/gcc/expmed.c b/gcc/expmed.c
index d591b6bc7c2b..ec2758ec8eff 100644
--- a/gcc/expmed.c
+++ b/gcc/expmed.c
@@ -2836,6 +2836,17 @@ choose_mult_variant (enum machine_mode mode, HOST_WIDE_INT val,
   struct mult_cost limit;
   int op_cost;
 
+  /* Fail quickly for impossible bounds.  */
+  if (mult_cost < 0)
+    return false;
+
+  /* Ensure that mult_cost provides a reasonable upper bound.
+     Any constant multiplication can be performed with less
+     than 2 * bits additions.  */
+  op_cost = 2 * GET_MODE_BITSIZE (mode) * add_cost[mode];
+  if (mult_cost > op_cost)
+    mult_cost = op_cost;
+
   *variant = basic_variant;
   limit.cost = mult_cost;
   limit.latency = mult_cost;