mu578 commented on code in PR #10724:
URL: https://github.com/apache/nuttx/pull/10724#discussion_r1331980388
##########
arch/risc-v/src/common/riscv_pmp.c:
##########
@@ -100,32 +101,6 @@ typedef struct pmp_entry_s pmp_entry_t;
* Private Functions
****************************************************************************/
-/****************************************************************************
- * Name: log2ceil
- *
- * Description:
- * Calculate the up-rounded power-of-two for input.
- *
- * Input Parameters:
- * size - The size of the PMP region.
- *
- * Returned Value:
- * Power-of-two for argument, rounded up.
- *
- ****************************************************************************/
-
-static uintptr_t log2ceil(uintptr_t size)
-{
- uintptr_t pot = 0;
-
- for (size = size - 1; size > 1; size >>= 1)
- {
- pot++;
- }
-
- return pot;
-}
-
Review Comment:
In `mu0` you have a bit_floor and bit_ceil implementation matching c++
definition. `__mu0_bit_floor_u8__` is performed on `unsigned long long`.
Meanwhile size of `uintptr_t` must be pounded defined i.e arch32 vs arch64.
https://github.com/mu578/mu0
https://en.cppreference.com/w/cpp/numeric/bit_floor
https://en.cppreference.com/w/cpp/numeric/bit_ceil
https://en.cppreference.com/w/cpp/numeric/bit_width
https://en.cppreference.com/w/cpp/numeric/countl_zero
example:
```c
__mu0_static_inline__
const ___mu0_uint8_t___ __mu0_bit_floor_u8__(const ___mu0_uint8_t___ __x)
{
# if MU0_HAVE_C99 || MU0_HAVE_CPP11
const ___mu0_uint8_t___ one = 1ULL;
const ___mu0_uint8_t___ zero = 0ULL;
# else
const ___mu0_uint8_t___ one = 1UL;
const ___mu0_uint8_t___ zero = 0UL;
# endif
return __x != zero ? (one << (__mu0_bit_width_u8__(__x) - one)) : zero;
}
```
edit, if there is no counting leading zero (i.e CLZ instruction) available
on one target here a fair soft fallback implementation (you may ignore my
MU0_HAVE_C99 || MU0_HAVE_CPP11, there are just here to trigger errors in case
of long long is not supported or is a language extension, e.g mainly CPP98-03
or prior C99 try to use):
```c
__mu0_static_inline__ const ___mu0_sint4_t___ __mu0_cntlz_u8__(const
___mu0_uint8_t___ __x);
__mu0_static_inline__ const ___mu0_sint4_t___ __mu0_cntlz_ux__(const
___mu0_uintx_t___ __x);
__mu0_static_inline__ const ___mu0_sint4_t___ __mu0_cntlz_u4__(const
___mu0_uint4_t___ __x);
__mu0_static_inline__ const ___mu0_sint4_t___ __mu0_cntlz_u2__(const
___mu0_uint2_t___ __x);
__mu0_static_inline__ const ___mu0_sint4_t___ __mu0_cntlz_u1__(const
___mu0_uint1_t___ __x);
__mu0_static_inline__
const ___mu0_sint4_t___ __mu0_cntlz_u8__(const ___mu0_uint8_t___ __x)
{
const ___mu0_sint4_t___ d = __mu0_bit_digits_u4__();
# if MU0_HAVE_C99 || MU0_HAVE_CPP11
return ((__x & 0xFFFFFFFF00000000ULL)
? __mu0_cntlz_u4__(__mu0_const_cast__(___mu0_uint4_t___,
(__x >> d)))
: d + __mu0_cntlz_u4__(__x & 0xFFFFFFFFULL)
);
# else
return ((__x & 0xFFFFFFFF00000000UL)
? __mu0_cntlz_u4__(__mu0_const_cast__(___mu0_uint4_t___,
(__x >> d)))
: d + __mu0_cntlz_u4__(__x & 0xFFFFFFFFUL)
);
# endif
}
# if MU0_HAVE_LP64
__mu0_static_inline__
const ___mu0_sint4_t___ __mu0_cntlz_ux__(const ___mu0_uintx_t___ __x)
{ return __mu0_cntlz_u8__(__x); }
# else
__mu0_static_inline__
const ___mu0_sint4_t___ __mu0_cntlz_ux__(const ___mu0_uintx_t___ __x)
{ return __mu0_cntlz_u4__(__x); }
# endif
__mu0_static_inline__
const ___mu0_sint4_t___ __mu0_cntlz_u4__(const ___mu0_uint4_t___ __x)
{
___mu0_uint1_t___ d = 0;
___mu0_uint4_t___ x = __x;
if (x) {
if (x & 0xFFFF0000U) { x = x >> 16U; } else { d += 16; }
return d + __mu0_cntlz_u2__ (x);
}
return __mu0_bit_digits_u4__();
}
```
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