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Re: [PATCH] x86 gas: allow 'rep nop'
- From: "Jan Beulich" <JBeulich at suse dot com>
- To: "Roland McGrath" <mcgrathr at google dot com>
- Cc: <binutils at sourceware dot org>
- Date: Tue, 03 Jul 2012 08:02:23 +0100
- Subject: Re: [PATCH] x86 gas: allow 'rep nop'
- References: <x57j395af77l.fsf@frobland.mtv.corp.google.com>
>>> On 02.07.12 at 18:39, Roland McGrath <mcgrathr@google.com> wrote:
> There is another 'rep;INSN' form that GCC likes to emit, this one
> 'rep;nop' as an alias for 'pause'. It's nicer to accept 'rep nop'
> for this one too.
As gcc has to detect the respective gas capability anyway, why
can't it use "pause" right away, and then on much older gas
versions too?
Jan
> Ok for trunk?
>
>
> Thanks,
> Roland
>
>
> gas/testsuite/
> 2012-07-02 Roland McGrath <mcgrathr@google.com>
>
> * gas/i386/rep-nop.d: New file.
> * gas/i386/rep-nop.s: New file.
> * gas/i386/i386.exp: Add the new test.
>
> opcodes/
> 2012-07-02 Roland McGrath <mcgrathr@google.com>
>
> * i386-opc.tbl: Add RepPrefixOk to nop.
>
> diff --git a/gas/testsuite/gas/i386/i386.exp b/gas/testsuite/gas/i386/i386.exp
> index 0049000..a954088 100644
> --- a/gas/testsuite/gas/i386/i386.exp
> +++ b/gas/testsuite/gas/i386/i386.exp
> @@ -266,6 +266,7 @@ if [expr ([istarget "i*86-*-*"] || [istarget "x86_64-*-*"]) &&
> [gas_32_check]]
> run_dump_test "pr12589-1"
> run_dump_test "rep-bsf"
> run_dump_test "rep-ret"
> + run_dump_test "rep-nop"
>
> set ASFLAGS "$old_ASFLAGS"
> }
> diff --git a/gas/testsuite/gas/i386/rep-nop.d b/gas/testsuite/gas/i386/rep-nop.d
> new file mode 100644
> index 0000000..a269c6e
> --- /dev/null
> +++ b/gas/testsuite/gas/i386/rep-nop.d
> @@ -0,0 +1,10 @@
> +#objdump: -d
> +#name: rep prefix on nop
> +
> +.*: +file format .*
> +
> +Disassembly of section .text:
> +
> +0+000 <foo>:
> +\s*[0-9a-f]+:\s+f3 90\s+pause\s*
> + \.\.\.
> diff --git a/gas/testsuite/gas/i386/rep-nop.s b/gas/testsuite/gas/i386/rep-nop.s
> new file mode 100644
> index 0000000..ed9d5ad
> --- /dev/null
> +++ b/gas/testsuite/gas/i386/rep-nop.s
> @@ -0,0 +1,3 @@
> + .text
> +foo: rep nop
> + .p2align 4,0
> diff --git a/opcodes/i386-opc.tbl b/opcodes/i386-opc.tbl
> index 7de61a7..54cc0d1 100644
> --- a/opcodes/i386-opc.tbl
> +++ b/opcodes/i386-opc.tbl
> @@ -504,7 +504,7 @@ nop, 1, 0xf1f, 0x0, 2, CpuNop,
> Modrm|No_bSuf|No_sSuf|No_ldSuf, { Reg16|Reg32|Reg
>
> // nop is actually "xchg %ax,%ax" in 16bit mode, "xchg %eax,%eax" in
> // 32bit mode and "xchg %rax,%rax" in 64bit mode.
> -nop, 0, 0x90, None, 1, 0, No_bSuf|No_wSuf|No_lSuf|No_sSuf|No_qSuf|No_ldSuf,
> { 0 }
> +nop, 0, 0x90, None, 1, 0,
> No_bSuf|No_wSuf|No_lSuf|No_sSuf|No_qSuf|No_ldSuf|RepPrefixOk, { 0 }
>
> // Protection control.
> arpl, 2, 0x63, None, 1, Cpu286|CpuNo64,
> Modrm|IgnoreSize|No_bSuf|No_lSuf|No_sSuf|No_qSuf|No_ldSuf, { Reg16,
> Reg16|Word|Unspecified|BaseIndex|Disp8|Disp16|Disp32 }
> diff --git a/opcodes/i386-tbl.h b/opcodes/i386-tbl.h
> index 89dfda4..2248c7b 100644
> --- a/opcodes/i386-tbl.h
> +++ b/opcodes/i386-tbl.h
> @@ -4142,7 +4142,7 @@ const insn_template i386_optab[] =
> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 } },
> { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1,
> - 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
> + 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0,
> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
> { { { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,