> -----Original Message-----
> From: Christophe Lyon <christophe.l...@linaro.org>
> Sent: 30 June 2020 14:32
> To: Kyrylo Tkachov <kyrylo.tkac...@arm.com>
> Cc: gcc-patches@gcc.gnu.org
> Subject: Re: [PATCH] arm: Warn if IRQ handler is not compiled with -
> mgeneral-regs-only [PR target/94743]
>
> On Tue, 30 Jun 2020 at 15:16, Kyrylo Tkachov <kyrylo.tkac...@arm.com>
> wrote:
> >
> > Hi Christophe,
> >
> > Sorry for the delay.
> >
> > > -----Original Message-----
> > > From: Gcc-patches <gcc-patches-boun...@gcc.gnu.org> On Behalf Of
> > > Christophe Lyon via Gcc-patches
> > > Sent: 29 April 2020 16:19
> > > To: gcc-patches@gcc.gnu.org
> > > Subject: [PATCH] arm: Warn if IRQ handler is not compiled with -
> mgeneral-
> > > regs-only [PR target/94743]
> > >
> > > The interrupt attribute does not guarantee that the FP registers are
> > > saved, which can result in problems difficult to debug.
> > >
> > > Saving the FP registers and status registers can be a large penalty,
> > > so it's probably not desirable to do that all the time.
> > >
> > > If the handler calls other functions, we'd likely need to save all of
> > > them, for lack of knowledge of which registers they actually use.
> > >
> > > This is even more obscure for the end-user when the compiler inserts
> > > calls to helper functions such as memcpy (some multilibs do use FP
> > > registers to speed it up).
> > >
> > > In the PR, we discussed adding routines in libgcc to save the FP
> > > context and saving only locally-clobbered FP registers, but I think
> > > this is too intrusive for stage 4.
> > >
> > > In the mean time, emit a warning to suggest re-compiling with
> > > -mgeneral-regs-only. Note that this can lead to errors if the code
> > > uses floating-point and -mfloat-abi=hard, eg:
> > > argument of type 'double' not permitted with -mgeneral-regs-only
> > >
> > > This can be troublesome for the user, but at least this would make
> > > them aware of the latent issue.
> > >
> > > The patch adds two testcases:
> > > - pr94734-1.c checks that a warning is emitted. One function can make
> > > implicit calls to runtime floating-point routines, the other one
> > > doesn't. We can improve the diagnostic later not to warn in the
> > > second case.
> > >
> > > - pr94734-2.c checks that no warning is emitted when using
> > > -mgeneral-regs-only.
> > >
> > > 2020-04-29 Christophe Lyon <christophe.l...@linaro.org>
> > >
> > > PR target/94743
> > > gcc/
> > > * config/arm/arm.c (arm_handle_isr_attribute): Warn if
> > > -mgeneral-regs-only is not used.
> > >
> > > gcc/testsuite/
> > > * gcc.target/arm/pr94743-1.c: New test.
> > > * gcc.target/arm/pr94743-2.c: New test.
> > > ---
> > > gcc/config/arm/arm.c | 5 +++++
> > > gcc/testsuite/gcc.target/arm/pr94743-1.c | 20 ++++++++++++++++++++
> > > gcc/testsuite/gcc.target/arm/pr94743-2.c | 17 +++++++++++++++++
> > > 3 files changed, 42 insertions(+)
> > > create mode 100644 gcc/testsuite/gcc.target/arm/pr94743-1.c
> > > create mode 100644 gcc/testsuite/gcc.target/arm/pr94743-2.c
> > >
> > > diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
> > > index 6a6e804..34aad1d 100644
> > > --- a/gcc/config/arm/arm.c
> > > +++ b/gcc/config/arm/arm.c
> > > @@ -7176,6 +7176,11 @@ arm_handle_isr_attribute (tree *node, tree
> name,
> > > tree args, int flags,
> > > name);
> > > *no_add_attrs = true;
> > > }
> > > + else if (TARGET_VFP_BASE)
> > > + {
> > > + warning (OPT_Wattributes, "FP registers might be clobbered
> > > despite %qE attribute: compile with -mgeneral-regs-only",
> > > + name);
> > > + }
> >
> > Let's use %< and %> to quote -mgeneral-regs-only properly.
> > Ok with that change.
>
> Hi Kyrill,
>
> Thanks for the review, however I have posted v2 here:
> https://gcc.gnu.org/pipermail/gcc-patches/2020-May/545747.html
> (you approved v1)
>
> It includes a few more testcases and updates to existing ones.
>
> Is v2 OK with the quotation marks fixed?
>
Oops, sorry. Yes that looks ok too (with the quotation fixed).
Kyrill
> Thanks
>
> Christophe
>
> > Thanks,
> > Kyrill
> >
> > > /* FIXME: the argument if any is checked for type attributes;
> > > should it be checked for decl ones? */
> > > }
> > > diff --git a/gcc/testsuite/gcc.target/arm/pr94743-1.c
> > > b/gcc/testsuite/gcc.target/arm/pr94743-1.c
> > > new file mode 100644
> > > index 0000000..67700c6
> > > --- /dev/null
> > > +++ b/gcc/testsuite/gcc.target/arm/pr94743-1.c
> > > @@ -0,0 +1,20 @@
> > > +/* PR target/94743 */
> > > +/* { dg-do compile } */
> > > +
> > > +typedef struct {
> > > + double fpdata[32];
> > > +} dummy_t;
> > > +
> > > +dummy_t global_d;
> > > +dummy_t global_d1;
> > > +
> > > +__attribute__ ((interrupt("IRQ"))) void IRQ_HDLR_Test(void)
> > > +{ /* { dg-warning { FP registers might be clobbered despite 'interrupt'
> > > attribute: compile with -mgeneral-regs-only} "" { target *-*-* } . } */
> > > + global_d.fpdata[3] += global_d.fpdata[3] * global_d1.fpdata[3];
> > > +}
> > > +
> > > +
> > > +__attribute__ ((interrupt("IRQ"))) void IRQ_HDLR_Test2(void)
> > > +{ /* { dg-warning { FP registers might be clobbered despite 'interrupt'
> > > attribute: compile with -mgeneral-regs-only} "" { target *-*-* } . } */
> > > + global_d.fpdata[3] = 1.0;
> > > +}
> > > diff --git a/gcc/testsuite/gcc.target/arm/pr94743-2.c
> > > b/gcc/testsuite/gcc.target/arm/pr94743-2.c
> > > new file mode 100644
> > > index 0000000..745fd36
> > > --- /dev/null
> > > +++ b/gcc/testsuite/gcc.target/arm/pr94743-2.c
> > > @@ -0,0 +1,17 @@
> > > +/* PR target/94743 */
> > > +/* { dg-do compile } */
> > > +/* { dg-options "-mgeneral-regs-only" } */
> > > +
> > > +typedef struct {
> > > + /* Do not use floating-point types, which are not be compatible with
> > > + -mgeneral-regs-only under -mfloat-abi=hard */
> > > + int fpdata[32];
> > > +} dummy_t;
> > > +
> > > +dummy_t global_d;
> > > +dummy_t global_d1;
> > > +
> > > +__attribute__ ((interrupt("IRQ"))) void IRQ_HDLR_Test(void)
> > > +{
> > > + global_d.fpdata[3] += global_d.fpdata[3] * global_d1.fpdata[3];
> > > +}
> > > --
> > > 2.7.4
> >
