On Thu, Jan 11, 2024 at 9:33 AM Fangrui Song <mask...@google.com> wrote:
>
> On 2024-01-11, Uros Bizjak wrote:
> >On Thu, Jan 11, 2024 at 4:44 AM Fangrui Song <mask...@google.com> wrote:
> >>
> >> Printing the raw symbol is useful in inline asm (e.g. in C++ to get the
> >> mangled name). Similar constraints are available in other targets (e.g.
> >> "S" for aarch64/riscv, "Cs" for m68k).
> >>
> >> There isn't a good way for x86 yet, e.g. "i" doesn't work for
> >> PIC/-mcmodel=large. This patch adds "z".
> >
> >Please use W-prefixed multi-letter constraint name.
> >
> >Uros.
>
> Sounds good. How about "Ws"?
Yes, LGTM.
Thanks,
Uros.
>
> (I've asked overse...@gcc.gnu.org whether I can get gcc access (I
> already have binutils-gdb/glibc access), so that I can land approved
> patches myself in the future)
>
>
> From ad7bf3dce026bf226e22ab709c9326c611a4b745 Mon Sep 17 00:00:00 2001
> From: Fangrui Song <mask...@google.com>
> Date: Wed, 10 Jan 2024 18:49:45 -0800
> Subject: [PATCH] i386: Add "Ws" constraint for symbolic address/label
> reference [PR105576]
>
> Printing the raw symbol is useful in inline asm (e.g. in C++ to get the
> mangled name). Similar constraints are available in other targets (e.g.
> "S" for aarch64/riscv, "Cs" for m68k).
>
> There isn't a good way for x86 yet, e.g. "i" doesn't work for
> PIC/-mcmodel=large. This patch adds "Ws". Here are possible use cases:
>
> ```
> namespace ns { extern int var; }
> asm (".pushsection .xxx,\"aw\"; .dc.a %0; .popsection" :: "S"(&var));
> asm (".reloc ., BFD_RELOC_NONE, %0" :: "S"(&var));
> ```
>
> gcc/ChangeLog:
>
> PR target/105576
> * config/i386/constraints.md: Define constraint "Ws".
> * doc/md.texi: Document it.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.target/i386/asm-raw-symbol.c: New testcase.
> ---
> gcc/config/i386/constraints.md | 4 ++++
> gcc/doc/md.texi | 4 ++++
> gcc/testsuite/gcc.target/i386/asm-raw-symbol.c | 13 +++++++++++++
> 3 files changed, 21 insertions(+)
> create mode 100644 gcc/testsuite/gcc.target/i386/asm-raw-symbol.c
>
> diff --git a/gcc/config/i386/constraints.md b/gcc/config/i386/constraints.md
> index 0c6e662df25..280e4c8e36c 100644
> --- a/gcc/config/i386/constraints.md
> +++ b/gcc/config/i386/constraints.md
> @@ -348,6 +348,10 @@ (define_constraint "Wf"
> to double word size."
> (match_operand 0 "x86_64_dwzext_immediate_operand"))
>
> +(define_constraint "Ws"
> + "A symbolic reference or label reference."
> + (match_code "const,symbol_ref,label_ref"))
> +
> (define_constraint "Z"
> "32-bit unsigned integer constant, or a symbolic reference known
> to fit that range (for immediate operands in zero-extending x86-64
> diff --git a/gcc/doc/md.texi b/gcc/doc/md.texi
> index 47a87d6ceec..b0c61925120 100644
> --- a/gcc/doc/md.texi
> +++ b/gcc/doc/md.texi
> @@ -4275,6 +4275,10 @@ require non-@code{VOIDmode} immediate operands).
> 128-bit integer constant where both the high and low 64-bit word
> satisfy the @code{e} constraint.
>
> +@item Ws
> +A symbolic reference or label reference.
> +You can use the @code{%p} modifier to print the raw symbol.
> +
> @item Z
> 32-bit unsigned integer constant, or a symbolic reference known
> to fit that range (for immediate operands in zero-extending x86-64
> diff --git a/gcc/testsuite/gcc.target/i386/asm-raw-symbol.c
> b/gcc/testsuite/gcc.target/i386/asm-raw-symbol.c
> new file mode 100644
> index 00000000000..b7854567dd9
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/asm-raw-symbol.c
> @@ -0,0 +1,13 @@
> +/* { dg-do compile } */
> +
> +extern int var;
> +
> +void
> +func (void)
> +{
> + __asm__ ("@ %p0" : : "Ws" (func));
> + __asm__ ("@ %p0" : : "Ws" (&var + 1));
> +}
> +
> +/* { dg-final { scan-assembler "@ func" } } */
> +/* { dg-final { scan-assembler "@ var\\+4" } } */
> --
> 2.43.0.275.g3460e3d667-goog
>
