| Message ID | 3484b7fcd2c74655bd685e5a7030c284@AcuMS.aculab.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | minmax: reduce compilation time | expand |
On Wed, Jul 24, 2024, at 16:33, David Laight wrote: > min3() and max3() were added to optimise nested min(x, min(y, z)) > sequences, bit only moved where the expansion was requiested. > > Add a separate implementation for 3 argument calls. > These are never required to generate constant expressiions to > remove that logic. > > Signed-off-by: David Laight <david.laight@aculab.com> This brings another 3x improvement in the size of the expansion and build speed. > +#define __cmp_once3(op, x, y, z, uniq) ({ \ > + typeof(x) __x_##uniq = (x); \ > + typeof(x) __y_##uniq = (y); \ > + typeof(x) __z_##uniq = (z); \ > + __cmp(op, __cmp(op, __x_##uniq, __y_##uniq), __z_##uniq); }) This still has a nested call to __cmp(), which makes the resulting expression bigger than necessary. The three typeof(x) should be x/y/z, right? Using __auto_type would avoid the bug and also remove one more variable expansion. Using another temporary variable, plus the use of __auto_type brings the example line from xen/setup.c down 750KB to 530KB, and the compile speed from 0.5s to 0.34s. #define __cmp_once3(op, x, y, z, uniq) ({ \ __auto_type __x_##uniq = (x); \ __auto_type __y_##uniq = (y); \ __auto_type __z_##uniq = (z); \ __auto_type __xy##uniq = __cmp(op, __x_##uniq, __y_##uniq); \ __cmp(op, __xy_##uniq, __z_##uniq); }) The __auto_type change can also be applied to the other typeof() in this file. Arnd
From: Arnd Bergmann > Sent: 24 July 2024 18:04 > > On Wed, Jul 24, 2024, at 16:33, David Laight wrote: > > min3() and max3() were added to optimise nested min(x, min(y, z)) > > sequences, bit only moved where the expansion was requiested. > > > > Add a separate implementation for 3 argument calls. > > These are never required to generate constant expressiions to > > remove that logic. > > > > Signed-off-by: David Laight <david.laight@aculab.com> > > This brings another 3x improvement in the size of the expansion > and build speed. > > > +#define __cmp_once3(op, x, y, z, uniq) ({ \ > > + typeof(x) __x_##uniq = (x); \ > > + typeof(x) __y_##uniq = (y); \ > > + typeof(x) __z_##uniq = (z); \ > > + __cmp(op, __cmp(op, __x_##uniq, __y_##uniq), __z_##uniq); }) > > This still has a nested call to __cmp(), which makes the > resulting expression bigger than necessary. > > The three typeof(x) should be x/y/z, right? Ooops... > Using __auto_type > would avoid the bug and also remove one more variable expansion. I'd thought that as well. But hadn't looked up the syntax. > Using another temporary variable, plus the use of __auto_type > brings the example line from xen/setup.c down 750KB to 530KB, > and the compile speed from 0.5s to 0.34s. > > #define __cmp_once3(op, x, y, z, uniq) ({ \ > __auto_type __x_##uniq = (x); \ > __auto_type __y_##uniq = (y); \ > __auto_type __z_##uniq = (z); \ > __auto_type __xy##uniq = __cmp(op, __x_##uniq, __y_##uniq); \ > __cmp(op, __xy_##uniq, __z_##uniq); }) > > The __auto_type change can also be applied to the other typeof() > in this file. True. David > > Arnd - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
diff --git a/include/linux/minmax.h b/include/linux/minmax.h index 2fb63efbeb0e..4bbc82c589cf 100644 --- a/include/linux/minmax.h +++ b/include/linux/minmax.h @@ -38,6 +38,11 @@ ((__is_ok_signed(x) && __is_ok_signed(y)) || \ (__is_ok_unsigned(x) && __is_ok_unsigned(y))) +/* Check three values for min3(), max3() and clamp() */ +#define __types_ok3(x, y, z) \ + ((__is_ok_signed(x) && __is_ok_signed(y) && __is_ok_signed(z)) || \ + (__is_ok_unsigned(x) && __is_ok_unsigned(y) && __is_ok_unsigned(z))) + #define __cmp_op_min < #define __cmp_op_max > @@ -90,13 +95,24 @@ */ #define umax(x, y) __careful_cmp(max, __zero_extend(x), __zero_extend(y)) +#define __cmp_once3(op, x, y, z, uniq) ({ \ + typeof(x) __x_##uniq = (x); \ + typeof(x) __y_##uniq = (y); \ + typeof(x) __z_##uniq = (z); \ + __cmp(op, __cmp(op, __x_##uniq, __y_##uniq), __z_##uniq); }) + +#define __careful_cmp3(op, x, y, z, uniq) ({ \ + static_assert(__types_ok3(x, y, z), \ + #op "3(" #x ", " #y ", " #z ") signedness error"); \ + __cmp_once3(op, x, y, z, uniq); }) + /** * min3 - return minimum of three values * @x: first value * @y: second value * @z: third value */ -#define min3(x, y, z) min((typeof(x))min(x, y), z) +#define min3(x, y, z) __careful_cmp3(min, x, y, z, __COUNTER__) /** * max3 - return maximum of three values @@ -104,7 +120,7 @@ * @y: second value * @z: third value */ -#define max3(x, y, z) max((typeof(x))max(x, y), z) +#define max3(x, y, z) __careful_cmp3(max, x, y, z, __COUNTER__) /** * min_t - return minimum of two values, using the specified type @@ -139,10 +155,9 @@ typeof(val) unique_val = (val); \ typeof(lo) unique_lo = (lo); \ typeof(hi) unique_hi = (hi); \ - _Static_assert(__if_constexpr((lo) <= (hi), (lo) <= (hi), true), \ + _Static_assert(__if_constexpr((lo) <= (hi), (lo) <= (hi), true), \ "clamp() low limit " #lo " greater than high limit " #hi); \ - _Static_assert(__types_ok(val, lo), "clamp() 'lo' signedness error"); \ - _Static_assert(__types_ok(val, hi), "clamp() 'hi' signedness error"); \ + _Static_assert(__types_ok3(val, lo, hi), "clamp() signedness error"); \ __clamp(unique_val, unique_lo, unique_hi); }) #define __careful_clamp(val, lo, hi) ({ \
min3() and max3() were added to optimise nested min(x, min(y, z)) sequences, bit only moved where the expansion was requiested. Add a separate implementation for 3 argument calls. These are never required to generate constant expressiions to remove that logic. Signed-off-by: David Laight <david.laight@aculab.com> --- include/linux/minmax.h | 25 ++++++++++++++++++++----- 1 file changed, 20 insertions(+), 5 deletions(-)