diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index f788ef87987..592b28cd5c8 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2008-08-22  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/36548
+	PR middle-end/37125
+	* fold-const.c (extract_muldiv_1): Optimize (X * C1) % C2 only
+	if the multiplication does not overflow.
+
 2008-08-21  Nathan Sidwell  <nathan@codesourcery.com>
 
 	* c-ppoutput.c (init_pp_output): Initialize src_line to 1.
diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index cba88267565..e6769a650a8 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -5930,9 +5930,20 @@ extract_muldiv_1 (tree t, tree c, enum tree_code code, tree wide_type,
 	 (C * 8) % 4 since we know that's zero.  */
       if ((code == TRUNC_MOD_EXPR || code == CEIL_MOD_EXPR
 	   || code == FLOOR_MOD_EXPR || code == ROUND_MOD_EXPR)
+	  /* If the multiplication can overflow we cannot optimize this.
+	     ???  Until we can properly mark individual operations as
+	     not overflowing we need to treat sizetype special here as
+	     stor-layout relies on this opimization to make
+	     DECL_FIELD_BIT_OFFSET always a constant.  */
+	  && (TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (t))
+	      || (TREE_CODE (TREE_TYPE (t)) == INTEGER_TYPE
+		  && TYPE_IS_SIZETYPE (TREE_TYPE (t))))
 	  && TREE_CODE (TREE_OPERAND (t, 1)) == INTEGER_CST
 	  && integer_zerop (const_binop (TRUNC_MOD_EXPR, op1, c, 0)))
-	return omit_one_operand (type, integer_zero_node, op0);
+	{
+	  *strict_overflow_p = true;
+	  return omit_one_operand (type, integer_zero_node, op0);
+	}
 
       /* ... fall through ...  */
 
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index ae16c70a1f3..061c21962fc 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2008-08-22  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/36548
+	PR middle-end/37125
+	* gcc.c-torture/execute/pr37125.c: New testcase.
+
 2008-08-22  Daniel Kraft  <d@domob.eu>
 
 	* gfortran.dg/used_before_typed_4.f90: New test.
diff --git a/gcc/testsuite/gcc.c-torture/execute/pr37125.c b/gcc/testsuite/gcc.c-torture/execute/pr37125.c
new file mode 100644
index 00000000000..f29209eb7aa
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/pr37125.c
@@ -0,0 +1,23 @@
+extern void abort (void);
+
+static inline unsigned int
+mod_rhs(int rhs)
+{
+  if (rhs == 0) return 1;
+  return rhs;
+}
+
+void func_44 (unsigned int p_45);
+void func_44 (unsigned int p_45)
+{
+  if (!((p_45 * -9) % mod_rhs (-9))) {
+      abort();
+  }
+}
+
+int main (void)
+{
+  func_44 (2);
+  return 0;
+}
+