Re: [PATCH 1/2] scripts/coccinelle: Add cpu_env.cocci_template script

[Philippe Mathieu-Daudé]

On 26/1/24 12:24, Paolo Bonzini wrote:
> On Fri, Jan 26, 2024 at 11:38 AM Philippe Mathieu-Daudé
> <philmd@linaro.org> wrote:
> > On 25/1/24 17:56, 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>
> > > ---
> > >    MAINTAINERS                               |  1 +
> > >    scripts/coccinelle/cpu_env.cocci_template | 60 +++++++++++++++++++++++
> > >    2 files changed, 61 insertions(+)
> > >    create mode 100644 scripts/coccinelle/cpu_env.cocci_template
> >
> >
> > > diff --git a/scripts/coccinelle/cpu_env.cocci_template 
> > > b/scripts/coccinelle/cpu_env.cocci_template
> > > new file mode 100644
> > > index 0000000000..53aa3a1fea
> > > --- /dev/null
> > > +++ b/scripts/coccinelle/cpu_env.cocci_template
> > > @@ -0,0 +1,60 @@
> > > +/*
> > > +
> > > + 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.
> > > +
> > > + SPDX-License-Identifier: GPL-2.0-or-later
> > > + SPDX-FileCopyrightText: Linaro Ltd 2024
> > > + SPDX-FileContributor: Philippe Mathieu-Daudé
> > > +
> > > + Usage as of v8.2.0:
> > > +
> > > + $ for targetdir in target/*; do test -d $targetdir || continue; \
> > > +       export target=${targetdir:7}; \
> > > +       sed \
> > > +           -e "s/__CPUArchState__/$( \
> > > +               git grep -h --no-line-number '@env: #CPU.*State' \
> > > +                   target/$target/cpu.h \
> > > +               | sed -n -e 's/.*\(CPU.*State\).\?/\1/p')/g" \
> > > +           -e "s/__ARCHCPU__/$( \
> > > +               git grep -h --no-line-number OBJECT_DECLARE_CPU_TYPE.*CPU \
> > > +                   target/$target/cpu-qom.h \
> > > +               | sed -n -e 's/.*(\(.*\), .*, .*)/\1/p')/g" \
> > > +           -e "s/__ARCH_CPU__/$( \
> > > +               git grep -h --no-line-number OBJECT_DECLARE_CPU_TYPE.*CPU \
> > > +                   target/$target/cpu-qom.h \
> > > +               | sed -n -e 's/.*(.*, .*, \(.*\))/\1/p')/g" \
> > > +       < scripts/coccinelle/cpu_env.cocci_template \
> > > +       > $TMPDIR/cpu_env_$target.cocci; \
> > > +       for dir in hw target/$target; do \
> > > +           spatch --macro-file scripts/cocci-macro-file.h \
> > > +                  --sp-file $TMPDIR/cpu_env_$target.cocci \
> > > +                  --keep-comments \
> > > +                  --dir $dir \
> > > +                  --in-place; \
> > > +       done; \
> > > +   done
> > > +
> > > +*/
> > > +
> > > +@ CPUState_arg_used @
> > > +CPUState *cs;
> > > +identifier cpu;
> > > +identifier env;
> > > +@@
> > > +-   __ARCHCPU__ *cpu = __ARCH_CPU__(cs);
> >
> > Here we remove ARCH_CPU(), ...
> >
> > > +-   __CPUArchState__ *env = &cpu->env;
> > > ++   __CPUArchState__ *env = cpu_env(cs);
> > > +    ... when != cpu
> > > +
> > > +@ depends on never CPUState_arg_used @
> > > +identifier obj;
> > > +identifier cpu;
> > > +identifier env;
> > > +@@
> > > +-   __ARCHCPU__ *cpu = __ARCH_CPU__(obj);
> > > +-   __CPUArchState__ *env = &cpu->env;
> > > ++   __CPUArchState__ *env = cpu_env(CPU(obj));
> >
> > ... but here we just change it by a CPU() QOM call.
> > So this 2nd change is just style cleanup.
>
> Can you also add a hunk that is
>
> CPUState *cs;
> @@
> -  CPU(cs)
> + cs
>
> to clean up on the second?  cpu_env(CPU(current_cpu)) is suboptimal
> and also a bit ugly.

These case should be cleaned because this is already a CPUState*:

+    CPUX86State *env = cpu_env(CPU(current_cpu));

+    CPUPPCState *env = cpu_env(CPU(first_cpu));

But these (instance_init and QOM visitors) can't, the argument
isn't a CPUState*:

 static void ev4_cpu_initfn(Object *obj)
 {
-    AlphaCPU *cpu = ALPHA_CPU(obj);
-    CPUAlphaState *env = &cpu->env;
+    CPUAlphaState *env = cpu_env(CPU(obj));

@@ -5186,8 +5179,7 @@ static char *x86_cpuid_get_vendor(Object *obj, 
Error **errp)
 static void x86_cpuid_set_vendor(Object *obj, const char *value,
                                  Error **errp)
 {
-    X86CPU *cpu = X86_CPU(obj);
-    CPUX86State *env = &cpu->env;
+    CPUX86State *env = cpu_env(CPU(obj));

That said, these visitors take a Object* param because they implement
the generic QOM visitor API, but we know the visitor are registered
on classes/objects implementing CPUState, so QOM cast macro is
redundant.