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RE: MIPS JAL/JALR to BAL transformation for Linux (o32 ABI)
- From: Adam Nemet <anemet at caviumnetworks dot com>
- To: "Fu, Chao-Ying" <fu at mips dot com>
- Cc: "Richard Sandiford" <rdsandiford at googlemail dot com>, <binutils at sourceware dot org>, "Lau, David" <davidlau at mips dot com>, "Garbacea, Ilie" <ilie at mips dot com>
- Date: Sat, 1 Aug 2009 12:57:39 -0700
- Subject: RE: MIPS JAL/JALR to BAL transformation for Linux (o32 ABI)
- References: <o7iqh8ra53.fsf@ropi.home> <94BD67F8AF3ED34FA362C662BA1F12C502BB5CFA@MTVEXCHANGE.mips.com>
Fu, Chao-Ying writes:
> > > +/* True if ABFD is for CPUs that are faster if jal/jalr is
> > converted to bal.
> > > + This should be safe for all architectures, but for now
> > we enable it
> > > + for RM9000, mips32, mips32r2, mips64, and mips64r2. */
> > > +#define JAL_JALR_TO_BAL_P(abfd) \
> > > + ( ((elf_elfheader (abfd)->e_flags & EF_MIPS_MACH) ==
> > E_MIPS_MACH_9000) \
> > > + || ((elf_elfheader (abfd)->e_flags & EF_MIPS_ARCH) ==
> > E_MIPS_ARCH_32) \
> > > + || ((elf_elfheader (abfd)->e_flags & EF_MIPS_ARCH) ==
> > E_MIPS_ARCH_32R2) \
> > > + || ((elf_elfheader (abfd)->e_flags & EF_MIPS_ARCH) ==
> > E_MIPS_ARCH_64) \
> > > + || ((elf_elfheader (abfd)->e_flags & EF_MIPS_ARCH) ==
> > E_MIPS_ARCH_64R2))
> >
> > I think this should be a negative predicate. As you say JALR->BAL
> > should be a profitable transformation on most CPUs.
>
> Yes. If everyone is ok, we can just set JAL_JALR_TO_BAL_P(abfd) to 1.
> (And, fix new test failures due to BAL mismatching.)
Just to be sure, what I said applies to JALR->BAL for Octeon. JAL->BAL is not
necessarily profitable on Octeon but I thought the relaxation code was
performing JALR->BAL or JALR->JAL and not JAL->BAL? Am I missing something
here?
Adam