On Thu, Jul 24, 2025 at 5:35 PM Artemiy Granat <a.gra...@ispras.ru> wrote:
>
> The regparm attribute does not affect code generation on x86-64 target.
> Despite this, regparm was accepted silently, unlike other calling
> convention attributes handled in the ix86_handle_cconv_attribute
> function.
>
> Due to lack of diagnostics, Linux kernel attempted to specify regparm(0)
> on vmread_error_trampoline declaration, which is supposed to be invoked
> with all arguments on stack:
> https://lore.kernel.org/all/20220928232015.745948-1-sea...@google.com/
This looks somehow familiar ;)
> To produce a warning for regparm in 64-bit mode, simply move the block
> that produces diagnostics above the block that handles the regparm
> attribute.
I agree we should warn for ignored regparm attribute.
> gcc/ChangeLog:
>
> * config/i386/i386-options.cc (ix86_handle_cconv_attribute):
> Move 64-bit mode check before regparm handling.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/abi/regparm1.C: Use regparm attribute only if not in
> 64-bit mode.
> * gcc.target/i386/20020224-1.c: Likewise.
> * gcc.target/i386/pr103785.c: Likewise.
> * gcc.target/i386/pr36533.c: Likewise.
> * gcc.target/i386/pr59099.c: Likewise.
> * gcc.target/i386/sibcall-8.c: Likewise.
> * gcc.target/i386/sw-1.c: Likewise.
> * gcc.target/i386/pr15184-2.c: Fix invalid comment.
> * gcc.target/i386/attributes-ignore.c: New test.
Please enable testcases that explicitly test regparm attribute only
for ix86 targets using ia32 target selector. They are irrelevant for
x86_64 anyway.
Uros.
> ---
> gcc/config/i386/i386-options.cc | 24 +++++++++----------
> gcc/testsuite/g++.dg/abi/regparm1.C | 9 ++++++-
> gcc/testsuite/gcc.target/i386/20020224-1.c | 10 ++++++--
> .../gcc.target/i386/attributes-ignore.c | 8 +++++++
> gcc/testsuite/gcc.target/i386/pr103785.c | 5 +++-
> gcc/testsuite/gcc.target/i386/pr15184-2.c | 2 +-
> gcc/testsuite/gcc.target/i386/pr36533.c | 24 +++++++++++++++----
> gcc/testsuite/gcc.target/i386/pr59099.c | 9 ++++++-
> gcc/testsuite/gcc.target/i386/sibcall-8.c | 14 +++++++----
> gcc/testsuite/gcc.target/i386/sw-1.c | 5 +++-
> 10 files changed, 83 insertions(+), 27 deletions(-)
> create mode 100644 gcc/testsuite/gcc.target/i386/attributes-ignore.c
>
> diff --git a/gcc/config/i386/i386-options.cc b/gcc/config/i386/i386-options.cc
> index d244b225afe..f07e8bc5303 100644
> --- a/gcc/config/i386/i386-options.cc
> +++ b/gcc/config/i386/i386-options.cc
> @@ -3613,6 +3613,18 @@ ix86_handle_cconv_attribute (tree *node, tree name,
> tree args, int,
> return NULL_TREE;
> }
>
> + if (TARGET_64BIT)
> + {
> + /* Do not warn when emulating the MS ABI. */
> + if ((TREE_CODE (*node) != FUNCTION_TYPE
> + && TREE_CODE (*node) != METHOD_TYPE)
> + || ix86_function_type_abi (*node) != MS_ABI)
> + warning (OPT_Wattributes, "%qE attribute ignored",
> + name);
> + *no_add_attrs = true;
> + return NULL_TREE;
> + }
> +
> /* Can combine regparm with all attributes but fastcall, and thiscall. */
> if (is_attribute_p ("regparm", name))
> {
> @@ -3646,18 +3658,6 @@ ix86_handle_cconv_attribute (tree *node, tree name,
> tree args, int,
> return NULL_TREE;
> }
>
> - if (TARGET_64BIT)
> - {
> - /* Do not warn when emulating the MS ABI. */
> - if ((TREE_CODE (*node) != FUNCTION_TYPE
> - && TREE_CODE (*node) != METHOD_TYPE)
> - || ix86_function_type_abi (*node) != MS_ABI)
> - warning (OPT_Wattributes, "%qE attribute ignored",
> - name);
> - *no_add_attrs = true;
> - return NULL_TREE;
> - }
> -
> /* Can combine fastcall with stdcall (redundant) and sseregparm. */
> if (is_attribute_p ("fastcall", name))
> {
> diff --git a/gcc/testsuite/g++.dg/abi/regparm1.C
> b/gcc/testsuite/g++.dg/abi/regparm1.C
> index c4710464acc..52ba8d8d9cf 100644
> --- a/gcc/testsuite/g++.dg/abi/regparm1.C
> +++ b/gcc/testsuite/g++.dg/abi/regparm1.C
> @@ -11,7 +11,10 @@ int fail;
>
> struct Base
> {
> - __attribute((regparm(3))) void
> +#ifndef __x86_64__
> + __attribute((regparm(3)))
> +#endif
> + void
> set(int *addr1, int *addr2)
> {
> if (this != save_this)
> @@ -34,7 +37,11 @@ struct Base
>
> int main()
> {
> +#ifndef __x86_64__
> void (__attribute((regparm(3))) Base::* pfm)(int *, int *) = &Base::set;
> +#else
> + void (Base::* pfm)(int *, int *) = &Base::set;
> +#endif
> __typeof (&Base::set) pfm2 = &Base::set;
> decltype (&Base::set) pfm3 = &Base::set;
> auto pfm4 = &Base::set;
> diff --git a/gcc/testsuite/gcc.target/i386/20020224-1.c
> b/gcc/testsuite/gcc.target/i386/20020224-1.c
> index 2905719fa62..0a21857fc0b 100644
> --- a/gcc/testsuite/gcc.target/i386/20020224-1.c
> +++ b/gcc/testsuite/gcc.target/i386/20020224-1.c
> @@ -15,13 +15,19 @@ typedef struct {
>
> A a;
>
> -A __attribute__ ((regparm (2)))
> +A
> +#ifndef __x86_64__
> +__attribute__ ((regparm (2)))
> +#endif
> foo (int x)
> {
> return a;
> }
>
> -int __attribute__ ((regparm (2)))
> +int
> +#ifndef __x86_64__
> +__attribute__ ((regparm (2)))
> +#endif
> bar (int x)
> {
> int r = foo(0).a2;
> diff --git a/gcc/testsuite/gcc.target/i386/attributes-ignore.c
> b/gcc/testsuite/gcc.target/i386/attributes-ignore.c
> new file mode 100644
> index 00000000000..93a3770842c
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/attributes-ignore.c
> @@ -0,0 +1,8 @@
> +/* { dg-do compile { target { ! ia32 } } } */
> +
> +void foo1(int i, int j) __attribute__((regparm(0))); /* { dg-warning
> "ignored" } */
> +void foo2(int i, int j) __attribute__((stdcall)); /* { dg-warning "ignored"
> } */
> +void foo3(int i, int j) __attribute__((fastcall)); /* { dg-warning "ignored"
> } */
> +void foo4(int i, int j) __attribute__((cdecl)); /* { dg-warning "ignored" }
> */
> +void foo5(int i, int j) __attribute__((thiscall)); /* { dg-warning "ignored"
> } */
> +void foo6(int i, int j) __attribute__((sseregparm)); /* { dg-warning
> "ignored" } */
> diff --git a/gcc/testsuite/gcc.target/i386/pr103785.c
> b/gcc/testsuite/gcc.target/i386/pr103785.c
> index 5503b965256..49d6c56f8d2 100644
> --- a/gcc/testsuite/gcc.target/i386/pr103785.c
> +++ b/gcc/testsuite/gcc.target/i386/pr103785.c
> @@ -11,7 +11,10 @@ struct wrapper_t
>
> struct wrapper_t **table;
>
> -__attribute__ ((weak, regparm (2)))
> +#ifndef __x86_64__
> +__attribute__ ((regparm (2)))
> +#endif
> +__attribute__ ((weak))
> void
> update (long k, long e)
> {
> diff --git a/gcc/testsuite/gcc.target/i386/pr15184-2.c
> b/gcc/testsuite/gcc.target/i386/pr15184-2.c
> index cb8201f9731..dd50c42b90d 100644
> --- a/gcc/testsuite/gcc.target/i386/pr15184-2.c
> +++ b/gcc/testsuite/gcc.target/i386/pr15184-2.c
> @@ -1,4 +1,4 @@
> -/* PR 15184 second two tests
> +/* PR 15184 second two tests */
> /* { dg-do compile { target ia32 } } */
> /* { dg-options "-O2 -march=pentiumpro" } */
> /* { dg-additional-options "-fno-PIE" { target ia32 } } */
> diff --git a/gcc/testsuite/gcc.target/i386/pr36533.c
> b/gcc/testsuite/gcc.target/i386/pr36533.c
> index 8d71ece199d..8699d262a59 100644
> --- a/gcc/testsuite/gcc.target/i386/pr36533.c
> +++ b/gcc/testsuite/gcc.target/i386/pr36533.c
> @@ -55,14 +55,22 @@ typedef struct
> S1 *s18;
> } S7;
>
> -__attribute__((regparm (3), noinline)) int
> +#ifndef __x86_64__
> +__attribute__((regparm (3)))
> +#endif
> +__attribute__((noinline))
> +int
> fn1 (const char *x, void *y, S1 *z)
> {
> asm volatile ("" : : : "memory");
> return *x + (y != 0);
> }
>
> -__attribute__((regparm (3), noinline)) int
> +#ifndef __x86_64__
> +__attribute__((regparm (3)))
> +#endif
> +__attribute__((noinline))
> +int
> fn2 (const char *x, int y, S2 *z)
> {
> asm volatile ("" : : : "memory");
> @@ -84,7 +92,11 @@ fn3 (S3 *p)
> return (S3 *) ((char *) p + fn4 (p->s9));
> }
>
> -__attribute__((regparm (3), noinline)) int
> +#ifndef __x86_64__
> +__attribute__((regparm (3)))
> +#endif
> +__attribute__((noinline))
> +int
> fn5 (void)
> {
> asm volatile ("" : : : "memory");
> @@ -116,7 +128,11 @@ fn6 (S3 *w, int x, S2 *y, S4 *z)
> return a;
> }
>
> -__attribute__((regparm (3), noinline)) unsigned int
> +#ifndef __x86_64__
> +__attribute__((regparm (3)))
> +#endif
> +__attribute__((noinline))
> +unsigned int
> test (void *u, S6 *v, S1 **w, S7 *x, S2 *y, S1 *z)
> {
> unsigned b = v->s17->s16;
> diff --git a/gcc/testsuite/gcc.target/i386/pr59099.c
> b/gcc/testsuite/gcc.target/i386/pr59099.c
> index cf4a8da7db1..21dfbc2defa 100644
> --- a/gcc/testsuite/gcc.target/i386/pr59099.c
> +++ b/gcc/testsuite/gcc.target/i386/pr59099.c
> @@ -13,10 +13,17 @@ struct s
> };
>
>
> -void* f (struct s *, struct s *) __attribute__ ((noinline, regparm(1)));
> +void* f (struct s *, struct s *)
> +#ifndef __x86_64__
> +__attribute__ ((regparm(1)))
> +#endif
> +__attribute__ ((noinline))
> +;
>
> void*
> +#ifndef __x86_64__
> __attribute__ ((regparm(1)))
> +#endif
> f (struct s *p, struct s *p2)
> {
> void *gp, *gp1;
> diff --git a/gcc/testsuite/gcc.target/i386/sibcall-8.c
> b/gcc/testsuite/gcc.target/i386/sibcall-8.c
> index 3ab3809036d..29ebfe59284 100644
> --- a/gcc/testsuite/gcc.target/i386/sibcall-8.c
> +++ b/gcc/testsuite/gcc.target/i386/sibcall-8.c
> @@ -1,23 +1,29 @@
> /* { dg-do run } */
> /* { dg-options "-O2" } */
>
> +#ifndef __x86_64__
> +#define REGPARM __attribute__((regparm(1)))
> +#else
> +#define REGPARM
> +#endif
> +
> extern void abort (void);
>
> -static int __attribute__((regparm(1)))
> +static int REGPARM
> bar(void *arg)
> {
> return arg != bar;
> }
>
> -static int __attribute__((noinline,noclone,regparm(1)))
> -foo(int (__attribute__((regparm(1))) **bar)(void*))
> +static int __attribute__((noinline,noclone)) REGPARM
> +foo(int (REGPARM **bar)(void*))
> {
> return (*bar)(*bar);
> }
>
> int main()
> {
> - int (__attribute__((regparm(1))) *p)(void*) = bar;
> + int (REGPARM *p)(void*) = bar;
> if (foo(&p))
> abort();
> return 0;
> diff --git a/gcc/testsuite/gcc.target/i386/sw-1.c
> b/gcc/testsuite/gcc.target/i386/sw-1.c
> index 14db3cee206..025f0e15d51 100644
> --- a/gcc/testsuite/gcc.target/i386/sw-1.c
> +++ b/gcc/testsuite/gcc.target/i386/sw-1.c
> @@ -7,7 +7,10 @@
>
> int c;
> int x[2000];
> -__attribute__((regparm(1))) void foo (int a, int b)
> +#ifndef __x86_64__
> +__attribute__((regparm(1)))
> +#endif
> +void foo (int a, int b)
> {
> int t[200];
> if (a == 0 || c == 0)
> --
> 2.50.1
>
