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[Bug target/38570] [arm] -mthumb generates sub-optimal prolog/epilog
- From: "rearnsha at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 4 May 2009 09:41:06 -0000
- Subject: [Bug target/38570] [arm] -mthumb generates sub-optimal prolog/epilog
- References: <bug-38570-17095@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #7 from rearnsha at gcc dot gnu dot org 2009-05-04 09:41 -------
(In reply to comment #6)
> We can compute the maximum possible function length first. If the length is not
> large enough far jump is not necessary, and we can do this optimization safely.
>
No, it's not that easy, since reload can add instructions.
Realistically, there is a finite limit beyond which even reload couldn't
generate sufficiently large numbers of instructions to cause failure, but it's
hard to *prove* what that lower bound is.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38570