Re: [PATCH v3 05/29] scripts/coccinelle: Add cpu_env.cocci script

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

On 29/1/24 17:44, Philippe Mathieu-Daudé wrote:
> Add a Coccinelle script to convert the following slow path
> (due to the QOM cast macro):
> 
>    &ARCH_CPU(..)->env
> 
> to the following fast path:
> 
>    cpu_env(..)
> 
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---

Changes since v2:

- Avoid templates by using coccinelle generic types
- Deal with uaccess API (by skipping functions using it)

>   MAINTAINERS                      |   1 +
>   scripts/coccinelle/cpu_env.cocci | 100 +++++++++++++++++++++++++++++++
>   2 files changed, 101 insertions(+)
>   create mode 100644 scripts/coccinelle/cpu_env.cocci
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index dfaca8323e..ca3c8c18ab 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -157,6 +157,7 @@ F: accel/tcg/
>   F: accel/stubs/tcg-stub.c
>   F: util/cacheinfo.c
>   F: util/cacheflush.c
> +F: scripts/coccinelle/cpu_env.cocci
>   F: scripts/decodetree.py
>   F: docs/devel/decodetree.rst
>   F: docs/devel/tcg*
> diff --git a/scripts/coccinelle/cpu_env.cocci b/scripts/coccinelle/cpu_env.cocci
> new file mode 100644
> index 0000000000..5a70c2211a
> --- /dev/null
> +++ b/scripts/coccinelle/cpu_env.cocci
> @@ -0,0 +1,100 @@
> +/*
> + * Convert &ARCH_CPU(..)->env to use cpu_env(..).
> + *
> + * Rationale: ARCH_CPU() might be slow, being a QOM cast macro.
> + *            cpu_env() is its fast equivalent.
> + *            CPU() macro is a no-op.
> + *
> + * SPDX-License-Identifier: GPL-2.0-or-later
> + * SPDX-FileCopyrightText: Linaro Ltd 2024
> + * SPDX-FileContributor: Philippe Mathieu-Daudé
> + */
> +
> +@@
> +type ArchCPU =~ "CPU$";
> +identifier cpu;
> +type CPUArchState =~ "^CPU";
> +identifier env;
> +@@
> +     ArchCPU *cpu;
> +     ...
> +     CPUArchState *env = &cpu->env;
> +     <...
> +-    &cpu->env
> ++    env
> +     ...>
> +
> +
> +/*
> + * Due to commit 8ce5c64499 ("semihosting: Return failure from
> + * softmmu-uaccess.h functions"), skip functions using softmmu-uaccess.h
> + * macros (they don't pass 'env' as argument).
> + */
> +@ uaccess_api_used exists @
> +identifier semihosting_func =~ "^(put|get)_user_[us](al|8|16|32)$";
> +@@
> +      semihosting_func(...)

Hmm, s/semihosting/uaccess/

> +
> +
> +/*
> + * Argument is CPUState*
> + */
> +@ cpustate_arg depends on !uaccess_api_used @
> +identifier cpu;
> +type ArchCPU =~ "CPU$";
> +type CPUArchState;
> +identifier ARCH_CPU =~ "CPU$";
> +identifier env;
> +CPUState *cs;
> +@@
> +-    ArchCPU *cpu = ARCH_CPU(cs);
> +     ...
> +-    CPUArchState *env = &cpu->env;
> ++    CPUArchState *env = cpu_env(cs);
> +     ... when != cpu
> +
> +
> +/*
> + * Argument is not CPUState* but a related QOM object.
> + * CPU() is not a QOM macro but a cast (See commit 0d6d1ab499).
> + */
> +@ depends on !uaccess_api_used  && !cpustate_arg @
> +identifier cpu;
> +type ArchCPU =~ "CPU$";
> +type CPUArchState;
> +identifier ARCH_CPU =~ "CPU$";
> +identifier env;
> +expression cs;
> +@@
> +-    ArchCPU *cpu = ARCH_CPU(cs);
> +     ...
> +-    CPUArchState *env = &cpu->env;
> ++    CPUArchState *env = cpu_env(CPU(cs));
> +     ... when != cpu
> +
> +
> +/* When single use of 'env', call cpu_env() in place */
> +@ depends on !uaccess_api_used @
> +type CPUArchState;
> +identifier env;
> +expression cs;
> +@@
> +-    CPUArchState *env = cpu_env(cs);
> +     ... when != env
> +-     env
> ++     cpu_env(cs)
> +     ... when != env
> +
> +
> +/* Both first_cpu/current_cpu are extern CPUState* */
> +@@
> +symbol first_cpu;
> +symbol current_cpu;
> +@@
> +(
> +-    CPU(first_cpu)
> ++    first_cpu
> +|
> +-    CPU(current_cpu)
> ++    current_cpu
> +)