On Sun, May 11, 2014 at 8:10 PM, Andreas Schwab <sch...@linux-m68k.org> wrote:
> Prathamesh Kulkarni <bilbotheelffri...@gmail.com> writes:
>
>> a) I am not able to follow why 3 slashes are required here
>> in x_.\\\(D\\\) ? Why does x_.\(D\) not work ?
>
> Two of the three backslashes are eaten by the tcl parser. But actually
> only two backslashes are needed, since the parens are not special to tcl
> (but are special to the regexp engine, so you want a single backslash
> surviving the tcl parser).
>
>> b) The expression after folding would be of the form:
>> t2_<digit> = x_<digit>(D) - y_<digit>(D)
>> I have used the operator "." in the pattern to match digit.
>> While that works in the above case, I think a better
>> idea would be to match using [0-9].
>> I tried the following but it does not work:
>> t_[0-9] = x_[0-9]\\\(D\\\) - y_[0-9]\\\(D\\\)
>> Neither does \\\[ and \\\] work.
>
> Brackets are special in tcl (including inside double quotes), so they
> need to be quoted. But you want the brackets to appear unquoted to the
> regexp engine, so a single backslash will do the Right Thing.
>
> See tcl(n) for the tcl parsing rules.
>
Thanks. Now I get it, the double backslash \\ is an escape sequence
for \, and special characters like (, [
retain their meaning in quotes, so to match input text: (D), the
pattern has to be written as: "\\(D\\)".
I believe "\(D\)" would only match D in the input ?
I have modified the test-case. Is this version correct ?
Thanks and Regards,
Prathamesh
> Andreas.
>
> --
> Andreas Schwab, sch...@linux-m68k.org
> GPG Key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5
> "And now for something completely different."
Index: gcc/testsuite/gcc.dg/tree-ssa/match-2.c
===================================================================
--- gcc/testsuite/gcc.dg/tree-ssa/match-2.c (revision 0)
+++ gcc/testsuite/gcc.dg/tree-ssa/match-2.c (working copy)
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-options "-O -fdump-tree-forwprop" } */
+
+int foo(int x, int y)
+{
+ int t1, t2;
+ t1 = -y;
+ t2 = x + t1;
+ return t2;
+}
+
+/* { dg-final { scan-tree-dump-times "t2_\[0-9\] = x_\[0-9\]\\(D\\) - y_\[0-9\]\\(D\\)" 1 "forwprop1" } } */
+/* { dg-final { cleanup-tree-dump "forwprop2" } } */
