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Re: assemble code and disassembled code in-consistency


On Fri, Jul 6, 2012 at 9:27 AM, Feng LI <nemokingdom@gmail.com> wrote:
> Hi folks,
>
> I have a backend hook (x86_64) for builtin function expansion, so
> I have this:
>
> expand_simple_binop (DImode, ASHIFT, op0,
>                                 GEN_INT (32),op0,1,OPTAB_DIRECT);
>
> to generate op0 = op0<<32 (op0 is the first argument of this builtin
> function, with type SIZE_T)
>
> The thing goes well in the assemble code, where I got:
>         movq    104(%rbx), %rax
>         salq    $32, %rax
>         addq    80(%rbx), %rax
>
> as expected.
>
> But at execution time, it gives me a strange behavior,
> So I disassemble the code,
>
> 401135:       48 8b 43 68             mov    0x68(%rbx),%rax
> 401140:       48 c1 e0 20             shl    $0x20,%rax
> 401144:       48 03 43 50             add    0x50(%rbx),%rax
>
> and it turns out salq are changed to shl which leads to the
> strange behavior. shl only allows shift less or equal than 31.
>

It is a binutils issue.


-- 
H.J.


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