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.
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
