Ping?
https://gcc.gnu.org/pipermail/gcc-patches/2020-May/545747.html
On Wed, 27 May 2020 at 13:52, Christophe Lyon
<christophe.l...@linaro.org> wrote:
>
> Ping?
>
> On Thu, 14 May 2020 at 16:57, Christophe Lyon
> <christophe.l...@linaro.org> wrote:
> >
> > 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 clobber.
> >
> > 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 this seems
> > to be too much work for the purpose, given that in general such
> > handlers try to avoid this kind of penalty.
> > I suspect we would also want new attributes to instruct the compiler
> > that saving the FP context is not needed.
> >
> > 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
> > him aware of the latent issue.
> >
> > The patch adds several testcases:
> >
> > - pr94734-1-hard.c checks that a warning is emitted when using
> > -mfloat-abi=hard. Function IRQ_HDLR_Test can make implicit calls to
> > runtime floating-point routines (or direct use of FP instructions),
> > IRQ_HDLR_Test2 doesn't. We emit a warning in both cases, though.
> >
> > - pr94734-1-softfp.c: same as above wih -mfloat-abi=softfp.
> >
> > - pr94734-1-soft.c checks that no warning is emitted when using
> > -mfloat-abi=soft when the same code as above.
> >
> > - pr94734-2.c checks that no warning is emitted when using
> > -mgeneral-regs-only.
> >
> > - pr94734-3.c checks that no warning is emitted when using
> > -mgeneral-regs-only even using float-point data.
> >
> > 2020-05-14 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.misc-tests/arm-isr.c: Add -mgeneral-regs-only.
> > * gcc.target/arm/empty_fiq_handler.c: Add -mgeneral-regs-only.
> > * gcc.target/arm/interrupt-1.c: Add -mgeneral-regs-only.
> > * gcc.target/arm/interrupt-2.c: Add -mgeneral-regs-only.
> > * gcc.target/arm/pr70830.c: Add -mgeneral-regs-only.
> > * gcc.target/arm/pr94743-1-hard.c: New test.
> > * gcc.target/arm/pr94743-1-soft.c: New test.
> > * gcc.target/arm/pr94743-1-softfp.c: New test.
> > * gcc.target/arm/pr94743-2.c: New test.
> > * gcc.target/arm/pr94743-3.c: New test.
> > ---
> > gcc/config/arm/arm.c | 5 ++++
> > gcc/testsuite/gcc.misc-tests/arm-isr.c | 2 ++
> > gcc/testsuite/gcc.target/arm/empty_fiq_handler.c | 1 +
> > gcc/testsuite/gcc.target/arm/interrupt-1.c | 2 +-
> > gcc/testsuite/gcc.target/arm/interrupt-2.c | 2 +-
> > gcc/testsuite/gcc.target/arm/pr70830.c | 2 +-
> > gcc/testsuite/gcc.target/arm/pr94743-1-hard.c | 29
> > ++++++++++++++++++++++++
> > gcc/testsuite/gcc.target/arm/pr94743-1-soft.c | 27
> > ++++++++++++++++++++++
> > gcc/testsuite/gcc.target/arm/pr94743-1-softfp.c | 29
> > ++++++++++++++++++++++++
> > gcc/testsuite/gcc.target/arm/pr94743-2.c | 22 ++++++++++++++++++
> > gcc/testsuite/gcc.target/arm/pr94743-3.c | 23 +++++++++++++++++++
> > 11 files changed, 141 insertions(+), 3 deletions(-)
> > create mode 100644 gcc/testsuite/gcc.target/arm/pr94743-1-hard.c
> > create mode 100644 gcc/testsuite/gcc.target/arm/pr94743-1-soft.c
> > create mode 100644 gcc/testsuite/gcc.target/arm/pr94743-1-softfp.c
> > create mode 100644 gcc/testsuite/gcc.target/arm/pr94743-2.c
> > create mode 100644 gcc/testsuite/gcc.target/arm/pr94743-3.c
> >
> > diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
> > index dda8771..c88de3e 100644
> > --- a/gcc/config/arm/arm.c
> > +++ b/gcc/config/arm/arm.c
> > @@ -7232,6 +7232,11 @@ 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);
> > + }
> > /* FIXME: the argument if any is checked for type attributes;
> > should it be checked for decl ones? */
> > }
> > diff --git a/gcc/testsuite/gcc.misc-tests/arm-isr.c
> > b/gcc/testsuite/gcc.misc-tests/arm-isr.c
> > index 737f9ff..9eff52c 100644
> > --- a/gcc/testsuite/gcc.misc-tests/arm-isr.c
> > +++ b/gcc/testsuite/gcc.misc-tests/arm-isr.c
> > @@ -1,3 +1,5 @@
> > +/* { dg-options "-mgeneral-regs-only" } */
> > +
> > extern void abort ();
> > extern void exit (int);
> >
> > diff --git a/gcc/testsuite/gcc.target/arm/empty_fiq_handler.c
> > b/gcc/testsuite/gcc.target/arm/empty_fiq_handler.c
> > index 8313f21..6911ffc 100644
> > --- a/gcc/testsuite/gcc.target/arm/empty_fiq_handler.c
> > +++ b/gcc/testsuite/gcc.target/arm/empty_fiq_handler.c
> > @@ -1,5 +1,6 @@
> > /* { dg-do compile } */
> > /* { dg-skip-if "" { ! arm_cortex_m } { "-mthumb" } } */
> > +/* { dg-options "-mgeneral-regs-only" } */
> >
> > /* Below code used to trigger an ICE due to missing constraints for
> > sp = fp + cst pattern. */
> > diff --git a/gcc/testsuite/gcc.target/arm/interrupt-1.c
> > b/gcc/testsuite/gcc.target/arm/interrupt-1.c
> > index 493763d..de1ecc5 100644
> > --- a/gcc/testsuite/gcc.target/arm/interrupt-1.c
> > +++ b/gcc/testsuite/gcc.target/arm/interrupt-1.c
> > @@ -2,7 +2,7 @@
> > __attribute__ ((interrupt)). */
> > /* { dg-do assemble } */
> > /* { dg-require-effective-target arm_nothumb } */
> > -/* { dg-options "-O0 -marm -save-temps" } */
> > +/* { dg-options "-mgeneral-regs-only -O0 -marm -save-temps" } */
> >
> > /* This test is not valid when -mthumb. */
> > extern void bar (int);
> > diff --git a/gcc/testsuite/gcc.target/arm/interrupt-2.c
> > b/gcc/testsuite/gcc.target/arm/interrupt-2.c
> > index 5be1f16..c64b98b 100644
> > --- a/gcc/testsuite/gcc.target/arm/interrupt-2.c
> > +++ b/gcc/testsuite/gcc.target/arm/interrupt-2.c
> > @@ -2,7 +2,7 @@
> > __attribute__ ((interrupt)). */
> > /* { dg-do assemble } */
> > /* { dg-require-effective-target arm_nothumb } */
> > -/* { dg-options "-O1 -marm -save-temps" } */
> > +/* { dg-options "-mgeneral-regs-only -O1 -marm -save-temps" } */
> >
> > /* This test is not valid when -mthumb. */
> > extern void bar (int);
> > diff --git a/gcc/testsuite/gcc.target/arm/pr70830.c
> > b/gcc/testsuite/gcc.target/arm/pr70830.c
> > index cd84c42..bca596c 100644
> > --- a/gcc/testsuite/gcc.target/arm/pr70830.c
> > +++ b/gcc/testsuite/gcc.target/arm/pr70830.c
> > @@ -1,7 +1,7 @@
> > /* PR target/70830. */
> > /* { dg-do assemble } */
> > /* { dg-require-effective-target arm_arm_ok } */
> > -/* { dg-options "-Os -marm -save-temps" } */
> > +/* { dg-options "-mgeneral-regs-only -Os -marm -save-temps" } */
> >
> > /* This test is not valid when -mthumb. */
> >
> > diff --git a/gcc/testsuite/gcc.target/arm/pr94743-1-hard.c
> > b/gcc/testsuite/gcc.target/arm/pr94743-1-hard.c
> > new file mode 100644
> > index 0000000..928b79d
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/arm/pr94743-1-hard.c
> > @@ -0,0 +1,29 @@
> > +/* PR target/94743 */
> > +/* { dg-do compile } */
> > +/* { dg-skip-if "do not override -mfloat-abi" { *-*-* } { "-mfloat-abi=*"
> > } {"-mfloat-abi=hard" } } */
> > +/* { dg-require-effective-target arm_vfp_ok } */
> > +/* { dg-add-options arm_vfp } */
> > +/* Make sure with use -mfloat-abi=hard. */
> > +/* { dg-additional-options "-mfloat-abi=hard" } */
> > +
> > +/* Check that we emit a warning when compiling an IRQ handler without
> > + -mgeneral-regs-only. */
> > +typedef struct {
> > + double fpdata[32];
> > +} dummy_t;
> > +
> > +dummy_t global_d;
> > +dummy_t global_d1;
> > +
> > +/* This function may clobber VFP registers. */
> > +__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];
> > +}
> > +
> > +/* This function does not need to clobber VFP registers. */
> > +/* Do we want to emit a (useless?) warning? */
> > +__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/pr94743-1-soft.c
> > b/gcc/testsuite/gcc.target/arm/pr94743-1-soft.c
> > new file mode 100644
> > index 0000000..e06a16d
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/arm/pr94743-1-soft.c
> > @@ -0,0 +1,27 @@
> > +/* PR target/94743 */
> > +/* { dg-do compile } */
> > +/* Thumb1 mode not supported for interrupt routines. */
> > +/* { dg-require-effective-target arm32 } */
> > +/* { dg-skip-if "do not override -mfloat-abi" { *-*-* } { "-mfloat-abi=*"
> > } {"-mfloat-abi=soft" } } */
> > +/* { dg-options "-mfloat-abi=soft" } */
> > +
> > +/* Check that we do not emit a warning when compiling an IRQ handler
> > without
> > + -mgeneral-regs-only with -mfloat-abi=soft. */
> > +typedef struct {
> > + double fpdata[32];
> > +} dummy_t;
> > +
> > +dummy_t global_d;
> > +dummy_t global_d1;
> > +
> > +/* This function may clobber VFP registers. */
> > +__attribute__ ((interrupt("IRQ"))) void IRQ_HDLR_Test(void)
> > +{
> > + global_d.fpdata[3] += global_d.fpdata[3] * global_d1.fpdata[3];
> > +}
> > +
> > +/* This function does not need to clobber VFP registers. */
> > +__attribute__ ((interrupt("IRQ"))) void IRQ_HDLR_Test2(void)
> > +{
> > + global_d.fpdata[3] = 1.0;
> > +}
> > diff --git a/gcc/testsuite/gcc.target/arm/pr94743-1-softfp.c
> > b/gcc/testsuite/gcc.target/arm/pr94743-1-softfp.c
> > new file mode 100644
> > index 0000000..6113eb6
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/arm/pr94743-1-softfp.c
> > @@ -0,0 +1,29 @@
> > +/* PR target/94743 */
> > +/* { dg-do compile } */
> > +/* { dg-skip-if "do not override -mfloat-abi" { *-*-* } { "-mfloat-abi=*"
> > } {"-mfloat-abi=softfp" } } */
> > +/* { dg-require-effective-target arm_vfp_ok } */
> > +/* { dg-add-options arm_vfp } */
> > +/* Make sure with use -mfloat-abi=softfp. */
> > +/* { dg-additional-options "-mfloat-abi=softfp" } */
> > +
> > +/* Check that we emit a warning when compiling an IRQ handler without
> > + -mgeneral-regs-only. */
> > +typedef struct {
> > + double fpdata[32];
> > +} dummy_t;
> > +
> > +dummy_t global_d;
> > +dummy_t global_d1;
> > +
> > +/* This function may clobber VFP registers. */
> > +__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];
> > +}
> > +
> > +/* This function does not need to clobber VFP registers. */
> > +/* Do we want to emit a (useless?) warning? */
> > +__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..50a97de
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/arm/pr94743-2.c
> > @@ -0,0 +1,22 @@
> > +/* PR target/94743 */
> > +/* { dg-do compile } */
> > +/* Thumb1 mode not supported for interrupt routines. */
> > +/* { dg-require-effective-target arm32 } */
> > +/* { dg-options "-mgeneral-regs-only" } */
> > +
> > +/* Check that we do not emit a warning when compiling an IRQ handler
> > + with -mgeneral-regs-only. */
> > +typedef struct {
> > + /* Do not use floating-point types, which are not compatible with
> > + -mgeneral-regs-only under -mfloat-abi=hard */
> > + int fpdata[32];
> > +} dummy_t;
> > +
> > +dummy_t global_d;
> > +dummy_t global_d1;
> > +
> > +/* This function does not clobber VFP registers. */
> > +__attribute__ ((interrupt("IRQ"))) void IRQ_HDLR_Test(void)
> > +{
> > + global_d.fpdata[3] += global_d.fpdata[3] * global_d1.fpdata[3];
> > +}
> > diff --git a/gcc/testsuite/gcc.target/arm/pr94743-3.c
> > b/gcc/testsuite/gcc.target/arm/pr94743-3.c
> > new file mode 100644
> > index 0000000..6b8ed2b
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/arm/pr94743-3.c
> > @@ -0,0 +1,23 @@
> > +/* PR target/94743 */
> > +/* { dg-do compile } */
> > +/* Thumb1 mode not supported for interrupt routines. */
> > +/* { dg-require-effective-target arm32 } */
> > +/* { dg-skip-if "do not override -mfloat-abi" { *-*-* } { "-mfloat-abi=*"
> > } {"-mfloat-abi=soft" } } */
> > +/* { dg-options "-mgeneral-regs-only -mfloat-abi=soft" } */
> > +
> > +/* Check that we do not emit a warning when compiling an IRQ handler
> > + with -mgeneral-regs-only even when using floating-point data. */
> > +typedef struct {
> > + /* Since we use -mfloat=abi=soft, this will generate calls to
> > + libgcc, but won't clobber VFP registers. */
> > + double fpdata[32];
> > +} dummy_t;
> > +
> > +dummy_t global_d;
> > +dummy_t global_d1;
> > +
> > +/* This function does not clobber VFP registers. */
> > +__attribute__ ((interrupt("IRQ"))) void IRQ_HDLR_Test(void)
> > +{
> > + global_d.fpdata[3] += global_d.fpdata[3] * global_d1.fpdata[3];
> > +}
> > --
> > 2.7.4
> >
