On Fri, Aug 15, 2025 at 12:44 AM Hongtao Liu <crazy...@gmail.com> wrote:
>
> On Fri, Aug 15, 2025 at 10:07 AM H.J. Lu <hjl.to...@gmail.com> wrote:
> >
> > Add target("80387") attribute to enable and disable x87 instructions in a
> > function.
> >
> > gcc/
> >
> > PR target/121541
> > * config/i386/i386-options.cc
> > (ix86_valid_target_attribute_inner_p): Add target("80387")
> > attribute. Set the mask bit in opts_set->x_target_flags if the
> > mask bit in opts->x_target_flags is updated.
> > * doc/extend.texi: Document target("80387") function attribute.
> >
> > gcc/testsuite/
> >
> > PR target/121541
> > * gcc.target/i386/pr121541-1a.c: New test.
> > * gcc.target/i386/pr121541-1b.c: Likewise.
> > * gcc.target/i386/pr121541-2.c: Likewise.
> > * gcc.target/i386/pr121541-3.c: Likewise.
> > * gcc.target/i386/pr121541-4.c: Likewise.
> > * gcc.target/i386/pr121541-5a.c: Likewise.
> > * gcc.target/i386/pr121541-5b.c: Likewise.
> >
> > Signed-off-by: H.J. Lu <hjl.to...@gmail.com>
> > ---
> > gcc/config/i386/i386-options.cc | 6 ++++++
> > gcc/doc/extend.texi | 5 +++++
> > gcc/testsuite/gcc.target/i386/pr121541-1a.c | 11 +++++++++++
> > gcc/testsuite/gcc.target/i386/pr121541-1b.c | 6 ++++++
> > gcc/testsuite/gcc.target/i386/pr121541-2.c | 11 +++++++++++
> > gcc/testsuite/gcc.target/i386/pr121541-3.c | 11 +++++++++++
> > gcc/testsuite/gcc.target/i386/pr121541-4.c | 11 +++++++++++
> > gcc/testsuite/gcc.target/i386/pr121541-5a.c | 11 +++++++++++
> > gcc/testsuite/gcc.target/i386/pr121541-5b.c | 6 ++++++
> > 9 files changed, 78 insertions(+)
> > create mode 100644 gcc/testsuite/gcc.target/i386/pr121541-1a.c
> > create mode 100644 gcc/testsuite/gcc.target/i386/pr121541-1b.c
> > create mode 100644 gcc/testsuite/gcc.target/i386/pr121541-2.c
> > create mode 100644 gcc/testsuite/gcc.target/i386/pr121541-3.c
> > create mode 100644 gcc/testsuite/gcc.target/i386/pr121541-4.c
> > create mode 100644 gcc/testsuite/gcc.target/i386/pr121541-5a.c
> > create mode 100644 gcc/testsuite/gcc.target/i386/pr121541-5b.c
> >
> > diff --git a/gcc/config/i386/i386-options.cc
> > b/gcc/config/i386/i386-options.cc
> > index 136c0f2e966..abb5dd7700e 100644
> > --- a/gcc/config/i386/i386-options.cc
> > +++ b/gcc/config/i386/i386-options.cc
> > @@ -1172,6 +1172,10 @@ ix86_valid_target_attribute_inner_p (tree fndecl,
> > tree args, char *p_strings[],
> > OPT_mrecip,
> > MASK_RECIP),
> >
> > + IX86_ATTR_YES ("80387",
> > + OPT_m80387,
> > + MASK_80387),
> > +
> > IX86_ATTR_IX86_YES ("general-regs-only",
> > OPT_mgeneral_regs_only,
> > OPTION_MASK_GENERAL_REGS_ONLY),
> > @@ -1281,6 +1285,8 @@ ix86_valid_target_attribute_inner_p (tree fndecl,
> > tree args, char *p_strings[],
> >
> > else if (type == ix86_opt_yes || type == ix86_opt_no)
> > {
> > + opts_set->x_target_flags |= mask;
> I don't think we should set opts_set here, opts_set is more readable only.
> I think we need to call ix86_handle_option here to rewrite opts when
> x87 is enabled(disable general regs in ix86_handle_optiion)
> Would that also solve the problem below?
ix86_handle_option always clears MASK_80387 for -mgeneral-regs-only.
But __attribute__ ((target("80387"))) overrides it by the code below.
For
gcc -O2 -mno-80387 -mgeneral-regs-only ...
we got here by
(gdb) bt
#0 ix86_option_override_internal (main_args_p=true,
opts=0x4898d40 <global_options>, opts_set=0x489a700 <global_options_set>)
at
/export/gnu/import/git/gitlab/x86-gcc/gcc/config/i386/i386-options.cc:2383
#1 0x000000000159c69c in ix86_option_override ()
at
/export/gnu/import/git/gitlab/x86-gcc/gcc/config/i386/i386-options.cc:3188
#2 0x0000000000e9f179 in process_options ()
at /export/gnu/import/git/gitlab/x86-gcc/gcc/toplev.cc:1293
global_options_set is set by
(gdb) bt
#0 set_option (opts=0x4898d40 <global_options>,
opts_set=0x489a700 <global_options_set>, opt_index=2062, value=0,
arg=0x0, kind=0, loc=0, dc=0x489c180 <global_diagnostic_context>, mask=0)
at /export/gnu/import/git/gitlab/x86-gcc/gcc/opts-common.cc:1763
#1 0x0000000002cb1041 in handle_option (opts=0x4898d40 <global_options>,
opts_set=0x489a700 <global_options_set>, decoded=0x48b5180, lang_mask=8,
kind=0, loc=0, handlers=0x7fffffffd990, generated_p=false,
dc=0x489c180 <global_diagnostic_context>)
at /export/gnu/import/git/gitlab/x86-gcc/gcc/opts-common.cc:1313
For __attribute__ ((target("80387"))), we got here by
#0 ix86_option_override_internal (main_args_p=false, opts=0x7fffffffb6f0,
opts_set=0x7fffffff9d30)
at
/export/gnu/import/git/gitlab/x86-gcc/gcc/config/i386/i386-options.cc:2383
#1 0x000000000158f1d9 in ix86_valid_target_attribute_tree (
fndecl=0x7fffe99cd900, args=0x7fffe99cb398, opts=0x7fffffffb6f0,
opts_set=0x7fffffff9d30, target_clone_attr=false)
at
/export/gnu/import/git/gitlab/x86-gcc/gcc/config/i386/i386-options.cc:1468
#2 0x000000000158f756 in ix86_valid_target_attribute_p (
fndecl=0x7fffe99cd900, name=0x7fffe99c9b40, args=0x7fffe99cb398, flags=0)
at
/export/gnu/import/git/gitlab/x86-gcc/gcc/config/i386/i386-options.cc:1569
(gdb) f 2
#2 0x000000000158f756 in ix86_valid_target_attribute_p (
fndecl=0x7fffe99cd900, name=0x7fffe99c9b40, args=0x7fffe99cb398, flags=0)
at
/export/gnu/import/git/gitlab/x86-gcc/gcc/config/i386/i386-options.cc:1569
1569 = ix86_valid_target_attribute_tree (fndecl, args, &func_options,
(gdb) list
1564 cl_target_option_restore (&func_options, &func_options_set,
1565 TREE_TARGET_OPTION (old_target));
1566
1567 /* FLAGS == 1 is used for target_clones attribute. */
1568 new_target
1569 = ix86_valid_target_attribute_tree (fndecl, args, &func_options,
1570 &func_options_set, flags == 1);
^^^^^^^^^^^^^^^^^^^^^^^^^^ opts_set.
1571
1572 new_optimize = build_optimization_node (&func_options,
&func_options_set);
1573
func_options_set was set by my patch earlier:
(gdb) bt
#0 ix86_valid_target_attribute_inner_p (fndecl=0x7fffe99cd900,
args=0x7fffe99bea40, p_strings=0x7fffffff9ca0, opts=0x7fffffffb6f0,
opts_set=0x7fffffff9d30, enum_opts_set=0x7fffffff82e0,
target_clone_attr=false)
at
/export/gnu/import/git/gitlab/x86-gcc/gcc/config/i386/i386-options.cc:1288
#1 0x000000000158e806 in ix86_valid_target_attribute_inner_p (
fndecl=0x7fffe99cd900, args=0x7fffe99cb398, p_strings=0x7fffffff9ca0,
opts=0x7fffffffb6f0, opts_set=0x7fffffff9d30,
enum_opts_set=0x7fffffff82e0, target_clone_attr=false)
at
/export/gnu/import/git/gitlab/x86-gcc/gcc/config/i386/i386-options.cc:1197
#2 0x000000000158f072 in ix86_valid_target_attribute_tree (
fndecl=0x7fffe99cd900, args=0x7fffe99cb398, opts=0x7fffffffb6f0,
opts_set=0x7fffffff9d30, target_clone_attr=false)
at
/export/gnu/import/git/gitlab/x86-gcc/gcc/config/i386/i386-options.cc:1426
#3 0x000000000158f756 in ix86_valid_target_attribute_p (
fndecl=0x7fffe99cd900, name=0x7fffe99c9b40, args=0x7fffe99cb398, flags=0)
at
/export/gnu/import/git/gitlab/x86-gcc/gcc/config/i386/i386-options.cc:1569
It was a mistake for ix86_valid_target_attribute_inner_p not to set
func_options_set when updating func_options when called from
/* FLAGS == 1 is used for target_clones attribute. */
new_target
= ix86_valid_target_attribute_tree (fndecl, args, &func_options,
&func_options_set, flags == 1);
It wasn't a problem before target("80387") is added since
ix86_handle_option ignores opts_set:
bool
ix86_handle_option (struct gcc_options *opts,
struct gcc_options *opts_set ATTRIBUTE_UNUSED,
const struct cl_decoded_option *decoded,
location_t loc)
and opts_set is checked only for MASK_80387.
> /* Don't enable x87 instructions if only general registers are
> allowed by target("general-regs-only") function attribute or
> -mgeneral-regs-only. */
> if (!(opts->x_ix86_target_flags & OPTION_MASK_GENERAL_REGS_ONLY)
> && !(opts_set->x_target_flags & MASK_80387))
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> When MASK_80387 in opts_set and opts are cleared by target("80387")
> function attribute, MASK_80387 will be turned on again without
> target("general-regs-only") function attribute nor -mgeneral-regs-only.
>
> {
> if (((processor_alias_table[i].flags & PTA_NO_80387) != 0))
> opts->x_target_flags &= ~MASK_80387;
> else
> opts->x_target_flags |= MASK_80387;
>
>
> > +
> > if (type == ix86_opt_no)
> > opt_set_p = !opt_set_p;
> >
> > diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
> > index 224d6197d63..e2771d7e36a 100644
> > --- a/gcc/doc/extend.texi
> > +++ b/gcc/doc/extend.texi
> > @@ -6798,6 +6798,11 @@ Enable/disable the generation of RCPSS, RCPPS,
> > RSQRTSS and RSQRTPS
> > instructions followed an additional Newton-Raphson step instead of
> > doing a floating-point division.
> >
> > +@cindex @code{target("80387")} function attribute, x86
> > +@item 80387
> > +@itemx no-80387
> > +Generate code containing 80387 instructions for floating point.
> > +
> > @cindex @code{target("general-regs-only")} function attribute, x86
> > @item general-regs-only
> > Generate code which uses only the general registers.
> > diff --git a/gcc/testsuite/gcc.target/i386/pr121541-1a.c
> > b/gcc/testsuite/gcc.target/i386/pr121541-1a.c
> > new file mode 100644
> > index 00000000000..83884a7b15c
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/i386/pr121541-1a.c
> > @@ -0,0 +1,11 @@
> > +/* { dg-do compile { target { ! ia32 } } } */
> > +/* { dg-options "-O2 -march=x86-64" } */
> > +
> > +extern long double d;
> > +
> > +__attribute__ ((target("no-80387")))
> > +void
> > +func1 (void)
> > +{
> > + d *= 3; /* { dg-error "x87 register return with x87 disabled" } */
> > +}
> > diff --git a/gcc/testsuite/gcc.target/i386/pr121541-1b.c
> > b/gcc/testsuite/gcc.target/i386/pr121541-1b.c
> > new file mode 100644
> > index 00000000000..f440b14ca71
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/i386/pr121541-1b.c
> > @@ -0,0 +1,6 @@
> > +/* { dg-do compile { target ia32 } } */
> > +/* { dg-options "-O2" } */
> > +
> > +#include "pr121541-1a.c"
> > +
> > +/* { dg-final { scan-assembler "call\[\\t \]+_?__mulxf3" } } */
> > diff --git a/gcc/testsuite/gcc.target/i386/pr121541-2.c
> > b/gcc/testsuite/gcc.target/i386/pr121541-2.c
> > new file mode 100644
> > index 00000000000..281341e9bb9
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/i386/pr121541-2.c
> > @@ -0,0 +1,11 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-O2 -mno-80387" } */
> > +
> > +extern long double d;
> > +
> > +__attribute__ ((target("80387")))
> > +void
> > +func1 (void)
> > +{
> > + d *= 3;
> > +}
> > diff --git a/gcc/testsuite/gcc.target/i386/pr121541-3.c
> > b/gcc/testsuite/gcc.target/i386/pr121541-3.c
> > new file mode 100644
> > index 00000000000..380fab2aad9
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/i386/pr121541-3.c
> > @@ -0,0 +1,11 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-O2 -mgeneral-regs-only" } */
> > +
> > +extern long double d;
> > +
> > +__attribute__ ((target("80387")))
> > +void
> > +func1 (void)
> > +{
> > + d *= 3;
> > +}
> > diff --git a/gcc/testsuite/gcc.target/i386/pr121541-4.c
> > b/gcc/testsuite/gcc.target/i386/pr121541-4.c
> > new file mode 100644
> > index 00000000000..1f4381a52b0
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/i386/pr121541-4.c
> > @@ -0,0 +1,11 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-O2" } */
> > +
> > +extern long double d;
> > +
> > +__attribute__ ((target("general-regs-only","80387")))
> > +void
> > +func1 (void)
> > +{
> > + d *= 3;
> > +}
> > diff --git a/gcc/testsuite/gcc.target/i386/pr121541-5a.c
> > b/gcc/testsuite/gcc.target/i386/pr121541-5a.c
> > new file mode 100644
> > index 00000000000..e6137e22e98
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/i386/pr121541-5a.c
> > @@ -0,0 +1,11 @@
> > +/* { dg-do compile { target { ! ia32 } } } */
> > +/* { dg-options "-O2 -march=x86-64" } */
> > +
> > +extern long double d;
> > +
> > +__attribute__ ((target("80387","general-regs-only")))
> > +void
> > +func1 (void)
> > +{
> > + d *= 3; /* { dg-error "x87 register return with x87 disabled" } */
> > +}
> > diff --git a/gcc/testsuite/gcc.target/i386/pr121541-5b.c
> > b/gcc/testsuite/gcc.target/i386/pr121541-5b.c
> > new file mode 100644
> > index 00000000000..b61a7fe6a3f
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/i386/pr121541-5b.c
> > @@ -0,0 +1,6 @@
> > +/* { dg-do compile { target ia32 } } */
> > +/* { dg-options "-O2" } */
> > +
> > +#include "pr121541-5a.c"
> > +
> > +/* { dg-final { scan-assembler "call\[\\t \]+_?__mulxf3" } } */
> > --
> > 2.50.1
> >
>
>
> --
> BR,
> Hongtao
--
H.J.
