+2013-10-25 Yufeng Zhang <yufeng.zhang@arm.com>
+
+ * tree-ssa-math-opts.c (convert_plusminus_to_widen): Call
+ has_single_use () and not do the conversion if has_single_use ()
+ returns false for the multiplication result.
+
2013-10-25 David Malcolm <dmalcolm@redhat.com>
* tree.h (EXCEPTIONAL_CLASS_P): Rename parameter from "CODE"
--- /dev/null
+/* Not to fuse widening multiply with accumulate if the multiply has more than
+ one uses.
+ Note that for targets where pointer and int are of the same size or
+ widening multiply-and-accumulate is not available, this test just passes. */
+
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-widening_mul" } */
+
+typedef int ArrT [10][10];
+
+void
+foo (ArrT Arr, int Idx)
+{
+ Arr[Idx][Idx] = 1;
+ Arr[Idx + 10][Idx] = 2;
+}
+
+/* { dg-final { scan-tree-dump-not "WIDEN_MULT_PLUS_EXPR" "widening_mul" } } */
+/* { dg-final { cleanup-tree-dump "widening_mul" } } */
It might also appear that it would be sufficient to use the existing
operands of the widening multiply, but that would limit the choice of
- multiply-and-accumulate instructions. */
+ multiply-and-accumulate instructions.
+
+ If the widened-multiplication result has more than one uses, it is
+ probably wiser not to do the conversion. */
if (code == PLUS_EXPR
&& (rhs1_code == MULT_EXPR || rhs1_code == WIDEN_MULT_EXPR))
{
- if (!is_widening_mult_p (rhs1_stmt, &type1, &mult_rhs1,
- &type2, &mult_rhs2))
+ if (!has_single_use (rhs1)
+ || !is_widening_mult_p (rhs1_stmt, &type1, &mult_rhs1,
+ &type2, &mult_rhs2))
return false;
add_rhs = rhs2;
conv_stmt = conv1_stmt;
}
else if (rhs2_code == MULT_EXPR || rhs2_code == WIDEN_MULT_EXPR)
{
- if (!is_widening_mult_p (rhs2_stmt, &type1, &mult_rhs1,
- &type2, &mult_rhs2))
+ if (!has_single_use (rhs2)
+ || !is_widening_mult_p (rhs2_stmt, &type1, &mult_rhs1,
+ &type2, &mult_rhs2))
return false;
add_rhs = rhs1;
conv_stmt = conv2_stmt;