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Use GCC builtins for bswap as compiler can then emit these via instructions.

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Using current macros, one get for:

static inline int BSWAP32(int x) {
	return ((x << 24) | ((x << 8) & 0x00FF0000) | ((x >> 8) & 0x0000FF00) | (x >> 24));
}
int main(int argc, char **argv)
{
  return BSWAP32(argc);
}

main:
.LFB1:
	.cfi_startproc
	movl	%edi, %eax
	movl	%edi, %edx
	sarl	$24, %edx
	sall	$24, %eax
	orl	%edx, %eax
	movl	%edi, %edx
	sarl	$8, %edi
	sall	$8, %edx
	andl	$65280, %edi
	andl	$16711680, %edx
	orl	%edx, %eax
	orl	%edi, %eax
	ret

while using:

int main(int argc, char **argv)
{
  return __builtin_bswap32(argc);
}

one gets:

main:
.LFB0:
	.cfi_startproc
	movl	%edi, %eax
	bswap	%eax
	ret
This commit is contained in:
marxin 2019-03-05 22:27:02 +01:00
parent c40877bc6a
commit 64bce5a24b
1 changed files with 14 additions and 1 deletions
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15
core/typedefs.h
View file

@ -250,21 +250,34 @@ static inline int get_shift_from_power_of_2(unsigned int p_pixel) {
}
/** Swap 16 bits value for endianness */
#if defined(__GNUC__) || _llvm_has_builtin(__builtin_bswap16)
#define BSWAP16(x) __builtin_bswap16(x)
#else
static inline uint16_t BSWAP16(uint16_t x) {
return (x >> 8) | (x << 8);
}
#endif
/** Swap 32 bits value for endianness */
#if defined(__GNUC__) || _llvm_has_builtin(__builtin_bswap32)
#define BSWAP32(x) __builtin_bswap32(x)
#else
static inline uint32_t BSWAP32(uint32_t x) {
return ((x << 24) | ((x << 8) & 0x00FF0000) | ((x >> 8) & 0x0000FF00) | (x >> 24));
}
/** Swap 64 bits value for endianness */
#endif
/** Swap 64 bits value for endianness */
#if defined(__GNUC__) || _llvm_has_builtin(__builtin_bswap64)
#define BSWAP64(x) __builtin_bswap64(x)
#else
static inline uint64_t BSWAP64(uint64_t x) {
x = (x & 0x00000000FFFFFFFF) << 32 | (x & 0xFFFFFFFF00000000) >> 32;
x = (x & 0x0000FFFF0000FFFF) << 16 | (x & 0xFFFF0000FFFF0000) >> 16;
x = (x & 0x00FF00FF00FF00FF) << 8 | (x & 0xFF00FF00FF00FF00) >> 8;
return x;
}
#endif
/** When compiling with RTTI, we can add an "extra"
* layer of safeness in many operations, so dynamic_cast