Re: [trunk][patch] fix another invalid sharing in see

["Rafael Espindola" <espindola at google dot com>]

>> Is the problem in this case that the copied subreg is being inserted
>> into the insn in two different places?
>
> This was fixed by the previous fix for the bug found by using
> enable-checking=rtl. I am dropping the patch.


The bug reappeared with another test (attached). The problem is on the
lines of what you think it is.  Before replace_rtx, ref_copy has the
node "(reg:SI 62 [ a ])" in two places. After it, the subreg is
present in those 2 places.

I can see 3 options:
1) ref_copy was already invalid and we should no be sharing "(reg:SI 62 [ a ])"
2) replace_rtx should create copies of "to" when replacing in more
then one place.
3) we have to fix ref_copy after replace_rtx.

I like 1, but verify_rtx_sharing says REGs can be shared, so there
might be a good reason for it. Changing replace_rtx sounds tempting,
but I am afraid to break something else.

The attached patch implements 3.

2008-05-26  Rafael Espindola  <espindola@google.com>

   * see.c (see_def_extension_not_merged): Use copy_rtx to avoid
invalid sharing.

   * gcc/testsuite/gcc.dg/20080526-1.c: New test.

OK if bootstraps and tests are OK?


Cheers,
-- 
Rafael Avila de Espindola

Google Ireland Ltd.
Gordon House
Barrow Street
Dublin 4
Ireland

Registered in Dublin, Ireland
Registration Number: 368047

Attachment: test.i
Description: Binary data

Attachment: see-fix4.patch
Description: Binary data