This is the mail archive of the
gcc-bugs@gcc.gnu.org
mailing list for the GCC project.
[Bug rtl-optimization/49936] [4.7 Regression] IRA handles CANNOT_CHANGE_MODE_CLASS poorly, + spills to memory on 4.7
- From: "vmakarov at redhat dot com" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Tue, 16 Aug 2011 02:05:02 +0000
- Subject: [Bug rtl-optimization/49936] [4.7 Regression] IRA handles CANNOT_CHANGE_MODE_CLASS poorly, + spills to memory on 4.7
- Auto-submitted: auto-generated
- References: <bug-49936-4@http.gcc.gnu.org/bugzilla/>
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49936
--- Comment #2 from Vladimir Makarov <vmakarov at redhat dot com> 2011-08-16 02:05:02 UTC ---
After thorough investigation of the problem I came to a conclusion that fixing
it in IRA requires to form regions on pseudo mode usage too (besides just
register pressure). Allocnos for the pseudo in question should get a different
classes (FP class inside loop and INT outside).
The problem is that IRA were written on assumption that register class of all
allocnos for a pseudo is the same. It needs a lot of changes besides a new
code for forming regions on the mode base.
I'll try to do this but it will take long time.
If it does not work, I could try to restore 4.6 behaviour (assigning INT class
instead of memory).