Re: [PATCH 2/6] x86-64: Intel64 adjustments for conditional jumps

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Fri, Mar 6, 2020 at 12:12 AM Jan Beulich <jbeulich@suse.com> wrote:
>
> Just like for unconditional direct JMP, AMD and Intel differ in their
> handling. Mirror JMP handling to Jcc.
>
> gas/
> 2020-03-XX  Jan Beulich  <jbeulich@suse.com>
>
>         * testsuite/gas/i386/x86-64-branch-2.s,
>         testsuite/gas/i386/x86-64-branch-3.s: Add Jcc cases.
>         * testsuite/gas/i386/ilp32/x86-64-branch.d,
>         testsuite/gas/i386/opcode-suffix.d,
>         testsuite/gas/i386/x86-64-branch-2.d,
>         testsuite/gas/i386/x86-64-branch-3.d,
>         testsuite/gas/i386/x86-64-branch.d: Adjust expectations.
>
> opcodes/
> 2020-03-XX  Jan Beulich  <jbeulich@suse.com>
>
>         * i386-dis.c (safe-ctype.h): Include.
>         (X86_64_0F8x): New enumerator.
>         (dis386): Extend comment ahead of it.
>         (dis386_twobyte): Vector Jcc to X86_64_0F8x.
>         (condition_code): New.
>         (x86_64_table): Add X86_64_0F8x entry.
>         (print_insn): Set condition_code. Move advancing of codep after
>         it.
>         (putop): Handle two-char escape case for 'C'. Handle 'C' prefix
>         case for 'P' and '@'.
>         * i386-opc.tbl (j<cc>): Split into AMD64 and Intel64 variants.
>         * i386-tbl.h: Re-generate.
> ---
> I wonder if the suffix handling done here wouldn't also be the more
> suitable one for JMP and CALL. In particular the 'q' suffix printed
> unconditionally in 64-bit mode is more of a problem than helpful imo.
>
> --- a/gas/testsuite/gas/i386/ilp32/x86-64-branch.d
> +++ b/gas/testsuite/gas/i386/ilp32/x86-64-branch.d
> @@ -22,7 +22,7 @@ Disassembly of section .text:
>  [      ]*[a-f0-9]+:    e9 00 00 00 00          jmpq   0x24     20: R_X86_64_PC32       \*ABS\*\+0x10003c
>  [      ]*[a-f0-9]+:    66 e8 00 00 00 00       data16 callq 0x2a       26: R_X86_64_PLT32      foo-0x4
>  [      ]*[a-f0-9]+:    66 e9 00 00 00 00       data16 jmpq 0x30        2c: R_X86_64_PLT32      foo-0x4
> -[      ]*[a-f0-9]+:    66 0f 82 00 00 00 00    data16 jb 0x37  33: R_X86_64_PLT32      foo-0x4
> +[      ]*[a-f0-9]+:    66 0f 82 00 00 00 00    data16 jbq 0x37 33: R_X86_64_PLT32      foo-0x4
>  [      ]*[a-f0-9]+:    66 c3                   data16 retq *
>  [      ]*[a-f0-9]+:    66 c2 08 00             data16 retq \$0x8
>  [      ]*[a-f0-9]+:    ff d0                   callq  \*%rax

I think it is a very bad idea to add suffix to jcc.

-- 
H.J.