mirror of /home/gitosis/repositories/libowfat.git
61 lines
1.3 KiB
C
61 lines
1.3 KiB
C
#if defined(__x86_64__) && defined(__OPTIMIZE__)
|
|
|
|
/* WARNING: this only works if compiled with -fomit-frame-pointer */
|
|
void umult64() {
|
|
asm volatile(
|
|
"xchgq %rdx,%rsi\n"
|
|
"movq %rdi,%rax\n"
|
|
"mulq %rdx\n"
|
|
"jc 1f\n" /* overflow */
|
|
"movq %rax,(%rsi)\n"
|
|
"xorq %rax,%rax\n"
|
|
"inc %rax\n"
|
|
"ret\n"
|
|
"1:\n"
|
|
"xorq %rax,%rax\n"
|
|
/* the closing ret is renerated by gcc */
|
|
);
|
|
}
|
|
|
|
#else
|
|
|
|
#include "safemult.h"
|
|
|
|
#if defined(__GNUC__) && (defined(__x86_64__) || defined(__ia64__) || defined(__powerpc64__) || defined(__alpha__) || defined(__mips64__) || defined(__sparc64__))
|
|
|
|
int umult64(uint64 a,uint64 b,uint64* c) {
|
|
__uint128_t x=((__uint128_t)a)*b;
|
|
if ((*c=(uint64)x) != x) return 0;
|
|
return 1;
|
|
}
|
|
|
|
#else
|
|
|
|
/* return 1 for overflow, 0 for ok */
|
|
int umult64(uint64 a,uint64 b,uint64* c) {
|
|
uint32 ahi=a>>32;
|
|
uint32 alo=(a&0xffffffff);
|
|
uint32 bhi=b>>32;
|
|
uint32 blo=(b&0xffffffff);
|
|
|
|
// a=ahi*x+alo, b=bhi*x+blo
|
|
// a*b = (ahi*x+alo) * (bhi*x+blo)
|
|
// = ahi*x*bhi*x + ahi*x*blo + alo*bhi*x + alo*blo
|
|
|
|
// -> overflow if ahi*bhi != zero */
|
|
if (ahi && bhi) return 0;
|
|
|
|
a=(uint64)(ahi)*blo+(uint64)(alo)*bhi;
|
|
if (a>0xffffffff) return 0;
|
|
{
|
|
uint64 x=(uint64)(alo)*blo;
|
|
if (x+(a<<32) < x) return 0;
|
|
*c=x+(a<<32);
|
|
}
|
|
return 1;
|
|
}
|
|
|
|
#endif
|
|
|
|
#endif
|