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Re: [PATCH 3/4] x86: Add -mindirect-branch-register
> 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?
Honza