Re: MSVC hook function prologue

[Paolo Bonzini <bonzini@gnu.org>]

>> Yes, you need this:
>>
>>       [(set (match_operand:SI 0 "register_operand" "=r")
>>             (match_operand:SI 1 "register_operand" "r"))
>>        (unspec_volatile [(const_int 0)] UNSPECV_VSWAPMOV)]
> That works, thanks!
>
> I just found the "=r" and "r" stuff myself almost at the same time your mail
> arrived. But what does the "SI" do? I haven't found

It specifies that the register must be 32-bit (SImode, Single-word 
Integer mode).  It just shuts up the warnings.

> Now the definition looks like this:
> (define_insn "vswapmov"
>    [(parallel
>      [(set (match_operand:SI 0 "register_operand" "=r")
>            (match_operand:SI 1 "register_operand" "r"))
>       (unspec_volatile [(const_int 0)] UNSPECV_VSWAPMOV)]
>     )]

The parallel is implicit in define_insn, so it is not different.  It 
does not make any harm I guess, but it looks "weird" to a more familiar 
eye. :-)

>    ""
>    "movl.s\t%1,%0"
>    [(set_attr "length" "2")
>     (set_attr "length_immediate" "0")
>     (set_attr "modrm" "0")])
>
> I am still compiling, so I don't know if it works yet.
>
> I attached the current state of the whole patch. I added the attribute to the
> documentation, and generated the patch with function names this time.

Here:

+#ifdef HAVE_AS_IX86_SWAP
+  { "msvc_prologue", 0, 0, false, true, true, ix86_handle_abi_attribute },
+#endif

it's better to always provide the attribute, and call "sorry" in 
ix86_function_msvc_prologue if you don't have the .s suffix.

Another two nits since I've found a more serious one: :-)

1) do not remove spurious lines.

        RTX_FRAME_RELATED_P (insn) = 1;
-
        insn = emit_move_insn (hard_frame_pointer_rtx, stack_pointer_rtx);
        RTX_FRAME_RELATED_P (insn) = 1;
-
        if (ix86_cfa_state->reg == stack_pointer_rtx)


2) extra long line, go to new line *before* ? and colon:

+  if (TARGET_64BIT ? is_attribute_p ("msvc_prologue", name) : 
!is_attribute_p ("msvc_prologue", name))

Thanks!!

Paolo