diff options
Diffstat (limited to 'src/include/cpu')
| -rw-r--r-- | src/include/cpu/x86/tsc.h | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/src/include/cpu/x86/tsc.h b/src/include/cpu/x86/tsc.h index 8e49a669eb..66451ad711 100644 --- a/src/include/cpu/x86/tsc.h +++ b/src/include/cpu/x86/tsc.h @@ -27,6 +27,19 @@ static inline tsc_t rdtsc(void) } #if !defined(__ROMCC__) +/* Simple 32- to 64-bit multiplication. Uses 16-bit words to avoid overflow. + * This code is used to prevent use of libgcc's umoddi3. + */ +static inline void multiply_to_tsc(tsc_t *const tsc, const u32 a, const u32 b) +{ + tsc->lo = (a & 0xffff) * (b & 0xffff); + tsc->hi = ((tsc->lo >> 16) + + ((a & 0xffff) * (b >> 16)) + + ((b & 0xffff) * (a >> 16))); + tsc->lo = ((tsc->hi & 0xffff) << 16) | (tsc->lo & 0xffff); + tsc->hi = ((a >> 16) * (b >> 16)) + (tsc->hi >> 16); +} + /* Too many registers for ROMCC */ static inline unsigned long long rdtscll(void) { |