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Re: [Patch][AArch64] - Error on load pair to same register

On 17/11/14 14:57, Ryan Mansfield wrote:
On 14-11-13 05:20 AM, Jiong Wang wrote:
On 12/11/14 20:07, Ryan Mansfield wrote:
I doubt that any one would intentionally do this operation since the
behaviour is unpredictable so it just seems safer to reject the code.
Hi Ryan,

    thanks for reporting  this.

    I think the encoding of same register is allowed in ISA manual, while
    the behavior is unpredictable. In principle, all allowed encoding need
    to be supported, while if its behavior is unpredictable, then we need
    to give warning instead of error which abort the assembling.
Hi Jiong,

Thanks for your comments. If it's a warning that should be issued, then
operand_general_constraint_met_p in libopcodes probably isn't the place
to be warning from, and better to handle it in md_assemble after the
operands have already been parsed.

I added some warnings about unpredictable writebacks as well. I realize
there's many more unpredictable conditions in the ARMv8 ARM. If anyone
feels like these are valuable to catch at assemble time, I can go and
add more checks.

2014-11-17  Ryan Mansfield  <>

          * config/tc-aarch64.c (md_assemble): Call warn_unpredictable.
          (warn_unpredictable): New.

2014-11-17  Ryan Mansfield  <>

          * gas/aarch64/diagnostic.s: Add new warnings test patterns.
          * gas/aarch64/diagnostic.l: Update expected diagnostic output.

thanks, this looks good to me.

but please wait gate keeper's final review and approval.


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