Re: [PATCH 0/9] bitfield: tidy up bitfield.h

David Laight
2025-12-11T10:51:12Z

On Wed, 10 Dec 2025 13:20:16 -0500
Yury Norov <yury.norov@gmail.com> wrote:

> On Tue, Dec 09, 2025 at 10:03:04AM +0000, david.laight.linux@gmail.com wrote:
> > From: David Laight <david.laight.linux@gmail.com>
...
> > I noticed some very long (18KB) error messages from the compiler.
> > Turned out they were errors on lines that passed GENMASK() to FIELD_PREP().
> > Since most of the #defines are already statement functions the values
> > can be copied to locals so the actual parameters only get expanded once.
> >
> > The 'bloat' is reduced further by using a simple test to ensure 'reg'
> > is large enough, slightly simplifying the test for constant 'val' and
> > only checking 'reg' and 'val' when the parameters are present.
>
> So, can you share the before/after?

Not that hard to generate since the kernel makefiles will create foo.i

I would have fed the .i file though xargs - but someone broke it
(there is no option to ignore quotes, and -s70 isn't allowed).
So I used:
tr ' ' '\n' foo.i | (ll=; while read -r l; do ll1="$ll $l"; [ ${#l} = 0 -o ${#ll1} -ge 70 ] && { echo "$ll"; ll="$l";} || ll="$ll1"; done; echo "$ll")

GENMASK(hi, lo)
((unsigned long)(((int)sizeof(struct
{_Static_assert(!(__builtin_choose_expr((sizeof(int) == sizeof(*(8 ?
((void *)((long)((lo) > (hi)) * 0l)) : (int *)8))), (lo) > (hi),
false)), "const_true((lo) > (hi))" " is true");})) +
(((typeof(unsigned long))((((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))) - 1) + ((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))))) << (lo) & ((typeof(unsigned
long))((((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long))
- 1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1))) -
1) + ((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long)) -
1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1)))))
>> ((sizeof(unsigned long) * 8) - 1 - (hi)))))

A chunk of that would be removed by changing type_max() to do
2 * (n - 1) + 1 instead of (n - 1) + n, but for unsigned types
it isn't needed.
Changing type_max(t) to (t)-1 GENMASK(hi, lo) becomes
(patch not posted...)
((unsigned long)(((int)sizeof(struct
{_Static_assert(!(__builtin_choose_expr((sizeof(int) == sizeof(*(8 ?
((void *)((long)((lo) > (hi)) * 0l)) : (int *)8))), (lo) > (hi),
false)), "const_true((lo) > (hi))" " is true");})) + ((unsigned long)-1
<< (lo) & (unsigned long)-1 >> ((sizeof(unsigned long) * 8) - 1 - (hi)))))
There are still four expansions of both lo and hi - but they are
usually trivial.

You asked for this one :-)
old FIELD_GET(GENMASK(hi, lo), reg)
({ do { __attribute__((__noreturn__)) extern void
__compiletime_assert_769(void) __attribute__((__error__("FIELD_GET: "
"type of reg too small for mask"))); if (!(!(((typeof(
_Generic((((unsigned long)(((int)sizeof(struct
{_Static_assert(!(__builtin_choose_expr((sizeof(int) == sizeof(*(8 ?
((void *)((long)((lo) > (hi)) * 0l)) : (int *)8))), (lo) > (hi),
false)), "const_true((lo) > (hi))" " is true");})) +
(((typeof(unsigned long))((((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))) - 1) + ((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))))) << (lo) & ((typeof(unsigned
long))((((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long))
- 1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1))) -
1) + ((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long)) -
1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1)))))
>> ((sizeof(unsigned long) * 8) - 1 - (hi)))))), char: (unsigned
char)0, unsigned char: (unsigned char)0, signed char: (unsigned
char)0, unsigned short: (unsigned short)0, signed short: (unsigned
short)0, unsigned int: (unsigned int)0, signed int: (unsigned int)0,
unsigned long: (unsigned long)0, signed long: (unsigned long)0,
unsigned long long: (unsigned long long)0, signed long long:
(unsigned long long)0, default: (((unsigned long)(((int)sizeof(struct
{_Static_assert(!(__builtin_choose_expr((sizeof(int) == sizeof(*(8 ?
((void *)((long)((lo) > (hi)) * 0l)) : (int *)8))), (lo) > (hi),
false)), "const_true((lo) > (hi))" " is true");})) +
(((typeof(unsigned long))((((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))) - 1) + ((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))))) << (lo) & ((typeof(unsigned
long))((((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long))
- 1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1))) -
1) + ((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long)) -
1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1)))))
>> ((sizeof(unsigned long) * 8) - 1 - (hi)))))))))(((unsigned
long)(((int)sizeof(struct
{_Static_assert(!(__builtin_choose_expr((sizeof(int) == sizeof(*(8 ?
((void *)((long)((lo) > (hi)) * 0l)) : (int *)8))), (lo) > (hi),
false)), "const_true((lo) > (hi))" " is true");})) +
(((typeof(unsigned long))((((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))) - 1) + ((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))))) << (lo) & ((typeof(unsigned
long))((((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long))
- 1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1))) -
1) + ((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long)) -
1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1)))))
>> ((sizeof(unsigned long) * 8) - 1 - (hi))))))) > ((typeof(
_Generic((reg), char: (unsigned char)0, unsigned char: (unsigned
char)0, signed char: (unsigned char)0, unsigned short: (unsigned
short)0, signed short: (unsigned short)0, unsigned int: (unsigned
int)0, signed int: (unsigned int)0, unsigned long: (unsigned long)0,
signed long: (unsigned long)0, unsigned long long: (unsigned long
long)0, signed long long: (unsigned long long)0, default:
(reg))))(~0ull))))) __compiletime_assert_769(); } while (0); ({ ({ do
{ __attribute__((__noreturn__)) extern void
__compiletime_assert_770(void) __attribute__((__error__("FIELD_GET: "
"mask is not constant"))); if (!(!(!__builtin_constant_p(((unsigned
long)(((int)sizeof(struct
{_Static_assert(!(__builtin_choose_expr((sizeof(int) == sizeof(*(8 ?
((void *)((long)((lo) > (hi)) * 0l)) : (int *)8))), (lo) > (hi),
false)), "const_true((lo) > (hi))" " is true");})) +
(((typeof(unsigned long))((((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))) - 1) + ((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))))) << (lo) & ((typeof(unsigned
long))((((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long))
- 1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1))) -
1) + ((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long)) -
1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1)))))
>> ((sizeof(unsigned long) * 8) - 1 - (hi)))))))))
__compiletime_assert_770(); } while (0); do {
__attribute__((__noreturn__)) extern void
__compiletime_assert_771(void) __attribute__((__error__("FIELD_GET: "
"mask is zero"))); if (!(!((((unsigned long)(((int)sizeof(struct
{_Static_assert(!(__builtin_choose_expr((sizeof(int) == sizeof(*(8 ?
((void *)((long)((lo) > (hi)) * 0l)) : (int *)8))), (lo) > (hi),
false)), "const_true((lo) > (hi))" " is true");})) +
(((typeof(unsigned long))((((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))) - 1) + ((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))))) << (lo) & ((typeof(unsigned
long))((((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long))
- 1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1))) -
1) + ((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long)) -
1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1)))))
>> ((sizeof(unsigned long) * 8) - 1 - (hi)))))) == 0)))
__compiletime_assert_771(); } while (0); do {
__attribute__((__noreturn__)) extern void
__compiletime_assert_772(void) __attribute__((__error__("FIELD_GET: "
"value too large for the field"))); if (!(!(__builtin_constant_p(0U)
? ~((((unsigned long)(((int)sizeof(struct
{_Static_assert(!(__builtin_choose_expr((sizeof(int) == sizeof(*(8 ?
((void *)((long)((lo) > (hi)) * 0l)) : (int *)8))), (lo) > (hi),
false)), "const_true((lo) > (hi))" " is true");})) +
(((typeof(unsigned long))((((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))) - 1) + ((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))))) << (lo) & ((typeof(unsigned
long))((((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long))
- 1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1))) -
1) + ((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long)) -
1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1)))))
>> ((sizeof(unsigned long) * 8) - 1 - (hi)))))) >>
(__builtin_ffsll(((unsigned long)(((int)sizeof(struct
{_Static_assert(!(__builtin_choose_expr((sizeof(int) == sizeof(*(8 ?
((void *)((long)((lo) > (hi)) * 0l)) : (int *)8))), (lo) > (hi),
false)), "const_true((lo) > (hi))" " is true");})) +
(((typeof(unsigned long))((((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))) - 1) + ((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))))) << (lo) & ((typeof(unsigned
long))((((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long))
- 1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1))) -
1) + ((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long)) -
1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1)))))
>> ((sizeof(unsigned long) * 8) - 1 - (hi)))))) - 1)) & (0 + (0U)) :
0))) __compiletime_assert_772(); } while (0); do {
__attribute__((__noreturn__)) extern void
__compiletime_assert_773(void) __attribute__((__error__("BUILD_BUG_ON
failed: " "(((((unsigned long)(((int)sizeof(struct
{_Static_assert(!(__builtin_choose_expr((sizeof(int) == sizeof(*(8 ?
((void *)((long)((lo) > (hi)) * 0l)) : (int *)8))), (lo) > (hi),
false)), \"const_true((lo) > (hi))\" \" is true\");})) +
(((typeof(unsigned long))((((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))) - 1) + ((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))))) << (lo) & ((typeof(unsigned
long))((((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long))
- 1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1))) -
1) + ((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long)) -
1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1)))))
>> ((sizeof(unsigned long) * 8) - 1 - (hi)))))) + (1ULL <<
(__builtin_ffsll(((unsigned long)(((int)sizeof(struct
{_Static_assert(!(__builtin_choose_expr((sizeof(int) == sizeof(*(8 ?
((void *)((long)((lo) > (hi)) * 0l)) : (int *)8))), (lo) > (hi),
false)), \"const_true((lo) > (hi))\" \" is true\");})) +
(((typeof(unsigned long))((((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))) - 1) + ((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))))) << (lo) & ((typeof(unsigned
long))((((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long))
- 1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1))) -
1) + ((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long)) -
1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1)))))
>> ((sizeof(unsigned long) * 8) - 1 - (hi)))))) - 1))) &
(((((unsigned long)(((int)sizeof(struct
{_Static_assert(!(__builtin_choose_expr((sizeof(int) == sizeof(*(8 ?
((void *)((long)((lo) > (hi)) * 0l)) : (int *)8))), (lo) > (hi),
false)), \"const_true((lo) > (hi))\" \" is true\");})) +
(((typeof(unsigned long))((((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))) - 1) + ((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))))) << (lo) & ((typeof(unsigned
long))((((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long))
- 1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1))) -
1) + ((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long)) -
1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1)))))
>> ((sizeof(unsigned long) * 8) - 1 - (hi)))))) + (1ULL <<
(__builtin_ffsll(((unsigned long)(((int)sizeof(struct
{_Static_assert(!(__builtin_choose_expr((sizeof(int) == sizeof(*(8 ?
((void *)((long)((lo) > (hi)) * 0l)) : (int *)8))), (lo) > (hi),
false)), \"const_true((lo) > (hi))\" \" is true\");})) +
(((typeof(unsigned long))((((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))) - 1) + ((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))))) << (lo) & ((typeof(unsigned
long))((((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long))
- 1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1))) -
1) + ((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long)) -
1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1)))))
>> ((sizeof(unsigned long) * 8) - 1 - (hi)))))) - 1))) - 1)) !=
0"))); if (!(!((((((unsigned long)(((int)sizeof(struct
{_Static_assert(!(__builtin_choose_expr((sizeof(int) == sizeof(*(8 ?
((void *)((long)((lo) > (hi)) * 0l)) : (int *)8))), (lo) > (hi),
false)), "const_true((lo) > (hi))" " is true");})) +
(((typeof(unsigned long))((((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))) - 1) + ((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))))) << (lo) & ((typeof(unsigned
long))((((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long))
- 1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1))) -
1) + ((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long)) -
1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1)))))
>> ((sizeof(unsigned long) * 8) - 1 - (hi)))))) + (1ULL <<
(__builtin_ffsll(((unsigned long)(((int)sizeof(struct
{_Static_assert(!(__builtin_choose_expr((sizeof(int) == sizeof(*(8 ?
((void *)((long)((lo) > (hi)) * 0l)) : (int *)8))), (lo) > (hi),
false)), "const_true((lo) > (hi))" " is true");})) +
(((typeof(unsigned long))((((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))) - 1) + ((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))))) << (lo) & ((typeof(unsigned
long))((((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long))
- 1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1))) -
1) + ((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long)) -
1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1)))))
>> ((sizeof(unsigned long) * 8) - 1 - (hi)))))) - 1))) &
(((((unsigned long)(((int)sizeof(struct
{_Static_assert(!(__builtin_choose_expr((sizeof(int) == sizeof(*(8 ?
((void *)((long)((lo) > (hi)) * 0l)) : (int *)8))), (lo) > (hi),
false)), "const_true((lo) > (hi))" " is true");})) +
(((typeof(unsigned long))((((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))) - 1) + ((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))))) << (lo) & ((typeof(unsigned
long))((((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long))
- 1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1))) -
1) + ((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long)) -
1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1)))))
>> ((sizeof(unsigned long) * 8) - 1 - (hi)))))) + (1ULL <<
(__builtin_ffsll(((unsigned long)(((int)sizeof(struct
{_Static_assert(!(__builtin_choose_expr((sizeof(int) == sizeof(*(8 ?
((void *)((long)((lo) > (hi)) * 0l)) : (int *)8))), (lo) > (hi),
false)), "const_true((lo) > (hi))" " is true");})) +
(((typeof(unsigned long))((((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))) - 1) + ((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))))) << (lo) & ((typeof(unsigned
long))((((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long))
- 1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1))) -
1) + ((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long)) -
1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1)))))
>> ((sizeof(unsigned long) * 8) - 1 - (hi)))))) - 1))) - 1)) != 0)))
__compiletime_assert_773(); } while (0); }); (typeof(((unsigned
long)(((int)sizeof(struct
{_Static_assert(!(__builtin_choose_expr((sizeof(int) == sizeof(*(8 ?
((void *)((long)((lo) > (hi)) * 0l)) : (int *)8))), (lo) > (hi),
false)), "const_true((lo) > (hi))" " is true");})) +
(((typeof(unsigned long))((((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))) - 1) + ((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))))) << (lo) & ((typeof(unsigned
long))((((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long))
- 1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1))) -
1) + ((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long)) -
1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1)))))
>> ((sizeof(unsigned long) * 8) - 1 - (hi)))))))(((reg) & (((unsigned
long)(((int)sizeof(struct
{_Static_assert(!(__builtin_choose_expr((sizeof(int) == sizeof(*(8 ?
((void *)((long)((lo) > (hi)) * 0l)) : (int *)8))), (lo) > (hi),
false)), "const_true((lo) > (hi))" " is true");})) +
(((typeof(unsigned long))((((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))) - 1) + ((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))))) << (lo) & ((typeof(unsigned
long))((((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long))
- 1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1))) -
1) + ((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long)) -
1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1)))))
>> ((sizeof(unsigned long) * 8) - 1 - (hi))))))) >>
(__builtin_ffsll(((unsigned long)(((int)sizeof(struct
{_Static_assert(!(__builtin_choose_expr((sizeof(int) == sizeof(*(8 ?
((void *)((long)((lo) > (hi)) * 0l)) : (int *)8))), (lo) > (hi),
false)), "const_true((lo) > (hi))" " is true");})) +
(((typeof(unsigned long))((((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))) - 1) + ((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))))) << (lo) & ((typeof(unsigned
long))((((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long))
- 1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1))) -
1) + ((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long)) -
1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1)))))
>> ((sizeof(unsigned long) * 8) - 1 - (hi)))))) - 1)); }); })

new FIELD_GET(GENMASK(hi, lo), reg)
({ __auto_type _mask = ((unsigned long)(((int)sizeof(struct
{_Static_assert(!(__builtin_choose_expr((sizeof(int) == sizeof(*(8 ?
((void *)((long)((lo) > (hi)) * 0l)) : (int *)8))), (lo) > (hi),
false)), "const_true((lo) > (hi))" " is true");})) +
(((typeof(unsigned long))((((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))) - 1) + ((typeof(unsigned long))1 <<
(8*sizeof(typeof(unsigned long)) - 1 - (((typeof(unsigned long))(-1))
< ( typeof(unsigned long))1))))) << (lo) & ((typeof(unsigned
long))((((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long))
- 1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1))) -
1) + ((typeof(unsigned long))1 << (8*sizeof(typeof(unsigned long)) -
1 - (((typeof(unsigned long))(-1)) < ( typeof(unsigned long))1)))))
>> ((sizeof(unsigned long) * 8) - 1 - (hi))))); __auto_type _reg =
reg; ({ do { do { __attribute__((__noreturn__)) extern void
__compiletime_assert_697(void) __attribute__((__error__("FIELD_GET: "
"mask is not constant"))); if (!(!(!__builtin_constant_p(_mask))))
__compiletime_assert_697(); } while (0); do {
__attribute__((__noreturn__)) extern void
__compiletime_assert_698(void) __attribute__((__error__("FIELD_GET: "
"mask is zero or not contiguous"))); if (!(!((!(_mask) || ((_mask) &
((_mask) + ((_mask) & -(_mask)))))))) __compiletime_assert_698(); }
while (0); } while (0); do { __attribute__((__noreturn__)) extern
void __compiletime_assert_699(void)
__attribute__((__error__("FIELD_GET: " "type of reg too small for
mask"))); if (!(!(_mask + 0U + 0UL + 0ULL > ~0ULL >> (64 - 8 * sizeof
(_reg))))) __compiletime_assert_699(); } while (0); ((_reg) &
(_mask)) >> (__builtin_ffsll(_mask) - 1); }); })

David