[PATCH v2] X86: disambiguate unqualified btr, bts

[Eli Friedman]

On Wed, Jul 10, 2013 at 11:47 PM, Ramkumar Ramachandra
<artagnon at gmail.com> wrote:
> The instructions btr and bts are perfectly valid, and have existed since
> Intel 386.  GNU as supports them fine, and there are instances of its
> usage in linux.git.  Unfortunately, LLVM does not support them, and
> barfs with:
>
>   error: ambiguous instructions require an explicit suffix
>
> Fix this problem by disambiguating it just like GNU as does, following
> the example set by 824a907.
>
> Cc: Eli Friedman <eli.friedman at gmail.com>
> Cc: Jim Grosbach <grosbach at apple.com>
> Cc: Chris Lattner <sabre at nondot.org>
> Signed-off-by: Ramkumar Ramachandra <artagnon at gmail.com>
> ---
>  FWIW, tests pass and clang goes past that point in linux.git.  Feel
>  free to tweak the justification before applying (I couldn't think of
>  anything else).
>
>  lib/Target/X86/X86InstrInfo.td | 4 ++++
>  test/MC/X86/x86-64.s           | 6 ++++++
>  2 files changed, 10 insertions(+)
>
> diff --git a/lib/Target/X86/X86InstrInfo.td b/lib/Target/X86/X86InstrInfo.td
> index f33ae2a..d1b8d15 100644
> --- a/lib/Target/X86/X86InstrInfo.td
> +++ b/lib/Target/X86/X86InstrInfo.td
> @@ -1971,6 +1971,10 @@ def : InstAlias<"aam", (AAM8i8 10)>;
>  // Disambiguate the mem/imm form of bt-without-a-suffix as btl.
>  def : InstAlias<"bt $imm, $mem", (BT32mi8 i32mem:$mem, i32i8imm:$imm)>;
>
> +// Disambiguate btr and bts, just like GNU as.
> +def : InstAlias<"btr $imm, $mem", (BTR16mi8 i16mem:$mem, i16i8imm:$imm)>;
> +def : InstAlias<"bts $imm, $mem", (BTS16mi8 i16mem:$mem, i16i8imm:$imm)>;
> +
>  // clr aliases.
>  def : InstAlias<"clrb $reg", (XOR8rr  GR8 :$reg, GR8 :$reg)>;
>  def : InstAlias<"clrw $reg", (XOR16rr GR16:$reg, GR16:$reg)>;
> diff --git a/test/MC/X86/x86-64.s b/test/MC/X86/x86-64.s
> index 521a077..9f89cda 100644
> --- a/test/MC/X86/x86-64.s
> +++ b/test/MC/X86/x86-64.s
> @@ -698,6 +698,12 @@ movl       0, %eax   // CHECK: movl 0, %eax # encoding: [0x8b,0x04,0x25,0x00,0x00,0x00
>  btl    $1, 0 // CHECK: btl $1, 0 # encoding: [0x0f,0xba,0x24,0x25,0x00,0x00,0x00,0x00,0x01]
>  bt     $1, 0 // CHECK: btl $1, 0 # encoding: [0x0f,0xba,0x24,0x25,0x00,0x00,0x00,0x00,0x01]
>
> +// Disambiguate btr, bts
> +btrw   $1, 0 // CHECK: btrw $1, 0 # encoding: [0x66,0x0f,0xba,0x34,0x25,0x00,0x00,0x00,0x00,0x01]
> +btr    $1, 0 // CHECK: btrw $1, 0 # encoding: [0x66,0x0f,0xba,0x34,0x25,0x00,0x00,0x00,0x00,0x01]
> +btsw   $1, 0 // CHECK: btsw $1, 0 # encoding: [0x66,0x0f,0xba,0x2c,0x25,0x00,0x00,0x00,0x00,0x01]
> +bts    $1, 0 // CHECK: btsw $1, 0 # encoding: [0x66,0x0f,0xba,0x2c,0x25,0x00,0x00,0x00,0x00,0x01]

This doesn't match gas.

-Eli