Re: [PATCH] target/arm: gdbstub: Guard M-profile code with CONFIG_TCG

[Peter Maydell]

On Tue, 4 Jul 2023 at 16:21, Philippe Mathieu-Daudé <philmd@linaro.org> wrote:
>
> On 28/6/23 18:48, Fabiano Rosas wrote:
> > This code is only relevant when TCG is present in the build. Building
> > with --disable-tcg --enable-xen on an x86 host we get:
> >
> > $ ../configure --target-list=x86_64-softmmu,aarch64-softmmu --disable-tcg 
> > --enable-xen
> > $ make -j$(nproc)
> > ...
> > libqemu-aarch64-softmmu.fa.p/target_arm_gdbstub.c.o: in function 
> > `m_sysreg_ptr':
> >   ../target/arm/gdbstub.c:358: undefined reference to `arm_v7m_get_sp_ptr'
> >   ../target/arm/gdbstub.c:361: undefined reference to `arm_v7m_get_sp_ptr'
> >
> > libqemu-aarch64-softmmu.fa.p/target_arm_gdbstub.c.o: in function 
> > `arm_gdb_get_m_systemreg':
> > ../target/arm/gdbstub.c:405: undefined reference to `arm_v7m_mrs_control'
> >
> > Signed-off-by: Fabiano Rosas <farosas@suse.de>
> > ---
> > This is a respin of:
> > https://lore.kernel.org/r/20230313151058.19645-5-farosas@suse.de
> > ---
> >   target/arm/gdbstub.c | 4 ++++
> >   1 file changed, 4 insertions(+)
> >
> > diff --git a/target/arm/gdbstub.c b/target/arm/gdbstub.c
> > index 03b17c814f..f421c5d041 100644
> > --- a/target/arm/gdbstub.c
> > +++ b/target/arm/gdbstub.c
> > @@ -324,6 +324,7 @@ static int arm_gen_dynamic_sysreg_xml(CPUState *cs, int 
> > base_reg)
> >       return cpu->dyn_sysreg_xml.num;
> >   }
> >
> > +#ifdef CONFIG_TCG
>
> OK.
>
> >   typedef enum {
> >       M_SYSREG_MSP,
> >       M_SYSREG_PSP,
> > @@ -481,6 +482,7 @@ static int arm_gen_dynamic_m_secextreg_xml(CPUState 
> > *cs, int orig_base_reg)
> >       return cpu->dyn_m_secextreg_xml.num;
> >   }
> >   #endif
> > +#endif /* CONFIG_TCG */
> >
> >   const char *arm_gdb_get_dynamic_xml(CPUState *cs, const char *xmlname)
> >   {
> > @@ -561,6 +563,7 @@ void arm_cpu_register_gdb_regs_for_features(ARMCPU *cpu)
> >                                arm_gen_dynamic_sysreg_xml(cs, 
> > cs->gdb_num_regs),
> >                                "system-registers.xml", 0);
> >
> > +#ifdef CONFIG_TCG
>
> IIUC tcg_enabled(), this guard shouldn't be necessary; if CONFIG_TCG
> is not defined, tcg_enabled() evaluates to 0, and the compiler should
> elide the whole block.

IME it's a bit optimistic to assume that the compiler will always
do that, especially with no optimisation enabled.

thanks
-- PMM