This is the mail archive of the
gcc-bugs@gcc.gnu.org
mailing list for the GCC project.
[Bug middle-end/32662] Significant extra code generation for 64x64=>128-bit multiply
- From: "rask at sygehus dot dk" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 7 Jul 2007 16:08:32 -0000
- Subject: [Bug middle-end/32662] Significant extra code generation for 64x64=>128-bit multiply
- References: <bug-32662-14600@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #4 from rask at sygehus dot dk 2007-07-07 16:08 -------
In reply to comment #1:
If you're splitting a multiword subreg (such as %rbx:%rcx) after reload, then
the prologue/epilogue code has no way of knowing that all use of %rbx is later
optimized away. I don't know if this is what's happening here, but that would
be the first thing I'd look for.
In reply to comment #2:
For both GCC 4.1.x and 4.2.x, the status is "regression fixes & docs only", so
unless some older release produced better code, this won't be fixed in GCC
4.1.x or 4.2.x.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32662