On Fri, 2016-09-02 at 15:41 -0400, Eric Gallager wrote:
> On 9/2/16, Segher Boessenkool <seg...@kernel.crashing.org> wrote:
> > On Fri, Sep 02, 2016 at 02:21:07PM -0400, Eric Gallager wrote:
> > > ../../gcc/combine.c: In function ‘int
> > > combine_instructions(rtx_insn*,
> > > unsigned int)’:
> > > ../../gcc/combine.c:1310:8: warning: ‘prev’ may be used
> > > uninitialized
> > > in this function [-Wmaybe-uninitialized]
> > > if ((next = try_combine (insn, prev, NULL, NULL,
> > > ^~
> >
> > That is:
> >
> > if (HAVE_cc0
> > && JUMP_P (insn)
> > && (prev = prev_nonnote_insn (insn)) != 0
> > && NONJUMP_INSN_P (prev)
> > && sets_cc0_p (PATTERN (prev)))
> > {
> > if ((next = try_combine (insn, prev, NULL, NULL,
> > &new_direct_jump_p,
> > last_combined_insn)) != 0)
> >
> > so prev is always initialised here. Could you try to find out why
> > GCC
> > warns anyway? Or open a PR?
> >
> > HAVE_cc0 probably expands to 0 (I'm not sure what your target is),
> > that
> > might have something to do with it.
> >
> >
> > Segher
> >
>
>
> My target is i386-apple-darwin9.8.0. If HAVE_cc0 expands to 0, then
> the code inside the brackets wouldn't even be reached anyways, would
> it? Where would HAVE_cc0 be defined?
It's defined in insn-config.h, which is generated in build/gcc by
genconfig from the target's machine description file.
