On Sun, Dec 16 2018 at 14:36:26 EET Bernd Edlinger wrote:
> Hi,
>
> if I understood that right, then clobbering sp is and has always been
> ignored.
>
> If that is right, then I would much prefer a warning, that says exactly
> that, because that would also help to understand why removing that clobber
> statement is safe even for old gcc versions.
>
> Since your patch did not actually change the handling of the PIC register,
> that one should of course stay an error.
Thank you. Looks like general consensus is to have a warning. See attached
patch that switches the error to a warning.
Regards,
Dimitar
>From d589ebd7824b4505ab75a2404f49a7c200679545 Mon Sep 17 00:00:00 2001
From: Dimitar Dimitrov <dimi...@dinux.eu>
Date: Sun, 16 Dec 2018 10:13:18 +0200
Subject: [PATCH] PR target/52813
Turns out there are existing programs that clobber stack pointer.
To avoid disruption, switch the newly introduced error to a warning.
Tested with:
$ make check-gcc-c RUNTESTFLAGS="i386.exp=pr52813.c "
gcc/ChangeLog:
2018-12-16 Dimitar Dimitrov <dimi...@dinux.eu>
* cfgexpand.c (asm_clobber_reg_is_valid): Switch error to warning.
Add clarification why there is a warning.
gcc/testsuite/ChangeLog:
2018-12-16 Dimitar Dimitrov <dimi...@dinux.eu>
* gcc.target/i386/pr52813.c (test1): Update warning message.
Signed-off-by: Dimitar Dimitrov <dimi...@dinux.eu>
---
gcc/cfgexpand.c | 7 +++++--
gcc/testsuite/gcc.target/i386/pr52813.c | 2 +-
2 files changed, 6 insertions(+), 3 deletions(-)
diff --git a/gcc/cfgexpand.c b/gcc/cfgexpand.c
index 0d04bbcafce..1e44c9a7ad0 100644
--- a/gcc/cfgexpand.c
+++ b/gcc/cfgexpand.c
@@ -2872,10 +2872,13 @@ asm_clobber_reg_is_valid (int regno, int nregs, const char *regname)
error ("PIC register clobbered by %qs in %<asm%>", regname);
is_valid = false;
}
- /* Clobbering the STACK POINTER register is an error. */
+ /* Clobbered STACK POINTER register is not saved/restored by GCC,
+ which is often unexpected by users. See PR52813. */
if (overlaps_hard_reg_set_p (regset, Pmode, STACK_POINTER_REGNUM))
{
- error ("Stack Pointer register clobbered by %qs in %<asm%>", regname);
+ warning (0, "Stack Pointer register clobbered by %qs in %<asm%>",
+ regname);
+ warning (0, "GCC has always ignored Stack Pointer %<asm%> clobbers");
is_valid = false;
}
diff --git a/gcc/testsuite/gcc.target/i386/pr52813.c b/gcc/testsuite/gcc.target/i386/pr52813.c
index 154ebbfc423..644fef15fef 100644
--- a/gcc/testsuite/gcc.target/i386/pr52813.c
+++ b/gcc/testsuite/gcc.target/i386/pr52813.c
@@ -5,5 +5,5 @@
void
test1 (void)
{
- asm volatile ("" : : : "%esp"); /* { dg-error "Stack Pointer register clobbered" } */
+ asm volatile ("" : : : "%esp"); /* { dg-warning "Stack Pointer register clobbered.\+GCC has always ignored Stack Pointer 'asm' clobbers" } */
}
--
2.11.0
