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Re: Dead-code elimination can't remove string copy insns?
Diego Novillo <dnovillo@redhat.com> writes:
> On Tue, 2003-05-13 at 12:17, Zack Weinberg wrote:
>> Michael Matz <matz@suse.de> writes:
>>
>> >> but the alias information should be sufficient to see that the memory
>> >> region being written into is on the stack, and unused past this insn,
>> >> hence the store is dead and can be deleted.
>> >
>> > It should, but we don't do that currently.
>>
>> Do you have a sense for how hard this would be to implement? Is it
>> something that's done on tree-ssa, so there's no point adding it in
>> mainline? Will Naveen's stack-slot allocator help?
>>
> If you show me the original source code I could tell you. Once things
> are in RTL form, it's difficult for me to trace them back into trees.
> There's also the situation in which we have dead code at the RTL level
> that it's impossible to detect at the tree level (e.g. address
> arithmetic for array references).
gcc.dg/const-elim-1.c. On an x86, compile it with -march=i386 -O2;
rs6000-ibm-aix5 and arm-elf also show the problem.
zw