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common.h: rename two alignment verification macros, add comments 

Zero functional change.

Rename "is_non0_power_of_2(x)" to "is_power_of_2(x)" because it's
simpler and because zero is not a power of 2.

Rename "compile_fail_zero_or_true(x)" to "compile_assert()" because it's
much simpler and because I really couldn't find what "zero_or_true"
meant?

Add a few comments, especially explain why COMPILE_TIME_ALIGNED(align)
uses __builtin_constant_p(align) because it took me ages to figure it
out.

Also recommend ALIGN_UP_COMPILE() over ALIGN_COMPILE() when compiling
with -O0

Signed-off-by: Marc Herbert <marc.herbert@intel.com>
This commit is contained in:
Marc Herbert 2021-01-23 01:40:39 +00:00 committed by Liam Girdwood
parent cdee91d01e
commit 921e52c680
1 changed files with 19 additions and 13 deletions
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32
src/include/sof/common.h
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@ -14,9 +14,10 @@
/* Align the number to the nearest alignment value */
#define IS_ALIGNED(size, alignment) ((size) % (alignment) == 0)
#define is_non0_power_of_2(x) ((x) && !((x) & ((x) - 1)))
/* Treat zero as a special case because it wraps around */
#define is_power_of_2(x) ((x) && !((x) & ((x) - 1)))
#define compile_fail_zero_or_true(x) (sizeof(struct{int _f : 1 - !(x); }))
#define compile_check(x) (sizeof(struct{int _f : 1 - !(x); }))
#define compile_fail_zero_or_false_fn(x) ({int _f[(x) - 1]; 0 & _f[0]; })
#define ALIGN_UP_INTERNAL(val, align) (((val) + (align) - 1) & ~((align) - 1))
@ -24,10 +25,14 @@
#define VERIFY_ALIGN
#ifdef VERIFY_ALIGN
/* For data initializers etc. */
/* Using this when 'alignment' is a constant and when compiling with gcc
* -O0 saves about 30 bytes of .text and a few CPU cycles compared to
* the ALIGN_UP() combined check. There's no .text difference when
* optimizing.
*/
#define ALIGN_UP_COMPILE(size, alignment) \
(compile_fail_zero_or_true(is_non0_power_of_2(alignment)) ? \
ALIGN_UP_INTERNAL(size, alignment) : 0)
(compile_check(is_power_of_2(alignment)) ? \
ALIGN_UP_INTERNAL(size, alignment) : 0xBADCAFE)
#ifdef __XCC__
@ -37,39 +42,40 @@
*/
#define ALIGN_UP(size, alignment) ({ \
if (!is_non0_power_of_2(alignment)) \
if (!is_power_of_2(alignment)) \
panic(SOF_IPC_PANIC_ASSERT); \
ALIGN_UP_INTERNAL(size, alignment); \
})
#define ALIGN_DOWN(size, alignment) ({ \
if (!is_non0_power_of_2(alignment)) \
if (!is_power_of_2(alignment)) \
panic(SOF_IPC_PANIC_ASSERT); \
(size) & ~((alignment) - 1); \
})
#else
#else /* not __XCC__ */
/* If we can't tell at compile time, assume it's OK and defer to run-time */
#define COMPILE_TIME_ALIGNED(align) (!__builtin_constant_p(align) || \
is_non0_power_of_2(align))
is_power_of_2(align))
#define ALIGN_UP(size, alignment) ({ \
if (compile_fail_zero_or_false_fn(COMPILE_TIME_ALIGNED(alignment)) || \
!is_non0_power_of_2(alignment)) \
!is_power_of_2(alignment)) \
panic(SOF_IPC_PANIC_ASSERT); \
ALIGN_UP_INTERNAL(size, alignment); \
})
#define ALIGN_DOWN(size, alignment) ({ \
if (compile_fail_zero_or_false_fn(COMPILE_TIME_ALIGNED(alignment)) || \
!is_non0_power_of_2(alignment)) \
!is_power_of_2(alignment)) \
panic(SOF_IPC_PANIC_ASSERT); \
(size) & ~((alignment) - 1); \
})
#endif
#endif /* not __XCC__ */
#else
#else /* not RUNTIME_ALIGN_CHECK */
#define ALIGN_UP(size, alignment) ALIGN_UP_INTERNAL(size, alignment)
#define ALIGN_UP_COMPILE ALIGN_UP