Yury Khrustalev <yury.khrusta...@arm.com> writes:
> From: Richard Ball <richard.b...@arm.com>
>
> This patch adds a new testcase and docs for indirect_return
> attribute.
>
> gcc/ChangeLog:
>
> * doc/extend.texi: Add AArch64 docs for indirect_return
> attribute.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.target/aarch64/indirect_return-1.c: New test.
> * gcc.target/aarch64/indirect_return-2.c: New test.
>
> Co-authored-by: Yury Khrustalev <yury.khrusta...@arm.com>
> ---
> gcc/doc/extend.texi | 10 ++++
> .../gcc.target/aarch64/indirect_return-1.c | 53 +++++++++++++++++++
> .../gcc.target/aarch64/indirect_return-2.c | 48 +++++++++++++++++
> 3 files changed, 111 insertions(+)
> create mode 100644 gcc/testsuite/gcc.target/aarch64/indirect_return-1.c
> create mode 100644 gcc/testsuite/gcc.target/aarch64/indirect_return-2.c
>
> diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
> index 5902e76f043..d3ce46e42e0 100644
> --- a/gcc/doc/extend.texi
> +++ b/gcc/doc/extend.texi
> @@ -4760,6 +4760,16 @@ Enable or disable calls to out-of-line helpers to
> implement atomic operations.
> This corresponds to the behavior of the command-line options
> @option{-moutline-atomics} and @option{-mno-outline-atomics}.
>
> +@cindex @code{indirect_return} function attribute, AArch64
> +@item indirect_return
> +The @code{indirect_return} attribute can be applied to a function type
> +to indicate that the function may return via an indirect branch instead
> +of via a normal return instruction. For example, this can be true of
> +functions that implement manual context switching between user space
> +threads, such as POSIX @code{swapcontext} function. This attribute adds
POSIX's (or "the POSIX @code{swapcontext} function").
> +a @code{BTI J} instruction when BTI is enabled e.g. via
> +@option{-mbranch-protection}.
> +
> @end table
>
> The above target attributes can be specified as follows:
> [...]
> diff --git a/gcc/testsuite/gcc.target/aarch64/indirect_return-2.c
> b/gcc/testsuite/gcc.target/aarch64/indirect_return-2.c
> new file mode 100644
> index 00000000000..58da4a5c082
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/aarch64/indirect_return-2.c
> @@ -0,0 +1,48 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O3 -mbranch-protection=none" } */
> +
> +int
> +__attribute((indirect_return,weak))
> +foo (int a)
> +{
> + return a;
> +}
> +
> +/*
> +**func1:
> +** ...
> +** bl foo
> +** ...
> +** ret
> +*/
> +int
> +func1 (int a, int b)
> +{
> + return foo (a + b);
> +}
> +
> +/*
> +**func2:
> +** ...
> +** b foo
> +*/
> +int __attribute((indirect_return,weak))
> +func2 (int a, int b)
> +{
> + return foo (a - b);
> +}
> +
> +/*
> +**func3:
> +** ...
> +** bl func2
> +** ...
> +** ret
> +*/
> +int
> +func3 (int x, int y)
> +{
> + return func2 (x, y);
> +}
> +
> +/* { dg-final { check-function-bodies "**" "" "" } } */
This doesn't verify that there are no hint instructions. Would adding:
/* { dg-final { scan-assembler-not {\thint\t} } } */
work?
LGTM otherwise.
Thanks,
Richard
