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-rw-r--r--include/asm-generic/div64.h81
1 files changed, 51 insertions, 30 deletions
diff --git a/include/asm-generic/div64.h b/include/asm-generic/div64.h
index 5a1bf1aff502..408856a9aba1 100644
--- a/include/asm-generic/div64.h
+++ b/include/asm-generic/div64.h
@@ -63,7 +63,7 @@
* do the trick here). \
*/ \
uint64_t ___res, ___x, ___t, ___m, ___n = (n); \
- uint32_t ___p, ___bias, ___m_lo, ___m_hi, ___n_lo, ___n_hi; \
+ uint32_t ___p, ___bias; \
\
/* determine MSB of b */ \
___p = 1 << ilog2(___b); \
@@ -138,41 +138,62 @@
* 2) whether or not there might be an overflow in the cross \
* product determined by (___m & ((1 << 63) | (1 << 31))). \
* \
- * Select the best way to do (m_bias + m * n) / (p << 64). \
+ * Select the best way to do (m_bias + m * n) / (1 << 64). \
* From now on there will be actual runtime code generated. \
*/ \
- \
- ___m_lo = ___m; \
- ___m_hi = ___m >> 32; \
- ___n_lo = ___n; \
- ___n_hi = ___n >> 32; \
- \
- if (!___bias) { \
- ___res = ((uint64_t)___m_lo * ___n_lo) >> 32; \
- } else if (!(___m & ((1ULL << 63) | (1ULL << 31)))) { \
- ___res = (___m + (uint64_t)___m_lo * ___n_lo) >> 32; \
- } else { \
- ___res = ___m + (uint64_t)___m_lo * ___n_lo; \
- ___t = (___res < ___m) ? (1ULL << 32) : 0; \
- ___res = (___res >> 32) + ___t; \
- } \
- \
- if (!(___m & ((1ULL << 63) | (1ULL << 31)))) { \
- ___res += (uint64_t)___m_lo * ___n_hi; \
- ___res += (uint64_t)___m_hi * ___n_lo; \
- ___res >>= 32; \
- } else { \
- ___t = ___res += (uint64_t)___m_lo * ___n_hi; \
- ___res += (uint64_t)___m_hi * ___n_lo; \
- ___t = (___res < ___t) ? (1ULL << 32) : 0; \
- ___res = (___res >> 32) + ___t; \
- } \
- \
- ___res += (uint64_t)___m_hi * ___n_hi; \
+ ___res = __arch_xprod_64(___m, ___n, ___bias); \
\
___res /= ___p; \
})
+#ifndef __arch_xprod_64
+/*
+ * Default C implementation for __arch_xprod_64()
+ *
+ * Prototype: uint64_t __arch_xprod_64(const uint64_t m, uint64_t n, bool bias)
+ * Semantic: retval = ((bias ? m : 0) + m * n) >> 64
+ *
+ * The product is a 128-bit value, scaled down to 64 bits.
+ * Assuming constant propagation to optimize away unused conditional code.
+ * Architectures may provide their own optimized assembly implementation.
+ */
+static inline uint64_t __arch_xprod_64(const uint64_t m, uint64_t n, bool bias)
+{
+ uint32_t m_lo = m;
+ uint32_t m_hi = m >> 32;
+ uint32_t n_lo = n;
+ uint32_t n_hi = n >> 32;
+ uint64_t res, tmp;
+
+ if (!bias) {
+ res = ((uint64_t)m_lo * n_lo) >> 32;
+ } else if (!(m & ((1ULL << 63) | (1ULL << 31)))) {
+ /* there can't be any overflow here */
+ res = (m + (uint64_t)m_lo * n_lo) >> 32;
+ } else {
+ res = m + (uint64_t)m_lo * n_lo;
+ tmp = (res < m) ? (1ULL << 32) : 0;
+ res = (res >> 32) + tmp;
+ }
+
+ if (!(m & ((1ULL << 63) | (1ULL << 31)))) {
+ /* there can't be any overflow here */
+ res += (uint64_t)m_lo * n_hi;
+ res += (uint64_t)m_hi * n_lo;
+ res >>= 32;
+ } else {
+ tmp = res += (uint64_t)m_lo * n_hi;
+ res += (uint64_t)m_hi * n_lo;
+ tmp = (res < tmp) ? (1ULL << 32) : 0;
+ res = (res >> 32) + tmp;
+ }
+
+ res += (uint64_t)m_hi * n_hi;
+
+ return res;
+}
+#endif
+
extern uint32_t __div64_32(uint64_t *dividend, uint32_t divisor);
/* The unnecessary pointer compare is there