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-rw-r--r--src/include/cpu/x86/tsc.h13
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)
{