On Fri, Jan 12, 2018 at 9:59 AM, Jan Hubicka <hubi...@ucw.cz> wrote:
>> Add -mindirect-branch-register to force indirect branch via register.
>> This is implemented by disabling patterns of indirect branch via memory,
>> similar to TARGET_X32.
>>
>> -mindirect-branch= and -mfunction-return= tests are updated with
>> -mno-indirect-branch-register to avoid false test failures when
>> -mindirect-branch-register is added to RUNTESTFLAGS for "make check".
>>
>> gcc/
>>
>> * config/i386/constraints.md (Bs): Disallow memory operand for
>> -mindirect-branch-register.
>> (Bw): Likewise.
>> * config/i386/predicates.md (indirect_branch_operand): Likewise.
>> (GOT_memory_operand): Likewise.
>> (call_insn_operand): Likewise.
>> (sibcall_insn_operand): Likewise.
>> (GOT32_symbol_operand): Likewise.
>> * config/i386/i386.md (indirect_jump): Call convert_memory_address
>> for -mindirect-branch-register.
>> (tablejump): Likewise.
>> (*sibcall_memory): Likewise.
>> (*sibcall_value_memory): Likewise.
>> Disallow peepholes of indirect call and jump via memory for
>> -mindirect-branch-register.
>> (*call_pop): Replace m with Bw.
>> (*call_value_pop): Likewise.
>> (*sibcall_pop_memory): Replace m with Bs.
>> * config/i386/i386.opt (mindirect-branch-register): New option.
>> * doc/invoke.texi: Document -mindirect-branch-register option.
>> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
>> index df945989fe8..d16006e653a 100644
>> --- a/gcc/doc/invoke.texi
>> +++ b/gcc/doc/invoke.texi
>> @@ -1230,7 +1230,8 @@ See RS/6000 and PowerPC Options.
>> -mstack-protector-guard-offset=@var{offset} @gol
>> -mstack-protector-guard-symbol=@var{symbol} -mmitigate-rop @gol
>> -mgeneral-regs-only -mcall-ms2sysv-xlogues @gol
>> --mindirect-branch=@var{choice} -mfunction-return==@var{choice}}
>> +-mindirect-branch=@var{choice} -mfunction-return==@var{choice} @gol
>> +-mindirect-branch-register}
>>
>> @emph{x86 Windows Options}
>> @gccoptlist{-mconsole -mcygwin -mno-cygwin -mdll @gol
>> @@ -26861,6 +26862,10 @@ object file. You can control this behavior for a
>> specific function by
>> using the function attribute @code{function_return}.
>> @xref{Function Attributes}.
>>
>> +@item -mindirect-branch-register
>> +@opindex -mindirect-branch-register
>> +Force indirect call and jump via register.
>
> Again I think this option needs better documentation. It is not quite clear
> to me why
> it is needed at first place?
>
This is used by kernel to force__x86_indirect_thunk_reg. Do we
need this info in GCC manual?
--
H.J.
