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Re: assemble code and disassembled code in-consistency


On Fri, Jul 6, 2012 at 9:47 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
> 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.

Hi Peter, Andi, Mark,

For some reason, binutils encodes sal the same as shl.  I'd
like to fix it.  Will it cause any problems?

Thanks.

-- 
H.J.


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