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RE: [PATCH] MIPS/GCC: Unconditional jump generation bug fix
- From: "Maciej W. Rozycki" <macro at codesourcery dot com>
- To: Matthew Fortune <Matthew dot Fortune at imgtec dot com>
- Cc: "Moore, Catherine" <Catherine_Moore at mentor dot com>, "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>, Eric Christopher <echristo at gmail dot com>
- Date: Wed, 19 Nov 2014 13:29:55 +0000
- Subject: RE: [PATCH] MIPS/GCC: Unconditional jump generation bug fix
- Authentication-results: sourceware.org; auth=none
- References: <alpine dot DEB dot 1 dot 10 dot 1411160038070 dot 2881 at tp dot orcam dot me dot uk> <6D39441BF12EF246A7ABCE6654B0235320F72B3D at LEMAIL01 dot le dot imgtec dot org> <alpine dot DEB dot 1 dot 10 dot 1411181647030 dot 2881 at tp dot orcam dot me dot uk> <6D39441BF12EF246A7ABCE6654B0235320F73B2A at LEMAIL01 dot le dot imgtec dot org> <FD3DCEAC5B03E9408544A1E416F11242018911622C at NA-MBX-01 dot mgc dot mentorg dot com> <6D39441BF12EF246A7ABCE6654B0235320F73C2C at LEMAIL01 dot le dot imgtec dot org>
On Tue, 18 Nov 2014, Matthew Fortune wrote:
> > > I admit to being a bit more nervous about 4.9 but the test coverage
> > > seems thorough enough. I guess I would have been less concerned if the
> > > optimisation was still just tied to TARGET_MICROMIPS for the 4.9
> > branch.
> > >
> > > Catherine, what do you think?
> > >
> > This is okay for 4.9 IMO.
>
> OK
FWIW we've been using this change since Oct 2012 with no issues (as I
noted it was meant to be included with the original microMIPS support
submission, but was lost in transit) and also GAS has code to relax
out-of-range branches to jumps in non-PIC standard MIPS code under the
same condition this RTL insn uses, so even if a wrong branch slipped
through here (which it doesn't), then GAS would fix it up.
See gas/config/tc-mips.c (md_apply_fix) <BFD_RELOC_16_PCREL_S2> for the
relaxation piece if interested.
Maciej