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authorLuis Pires <luis.pires@eldorado.org.br>2021-10-29 16:24:07 -0300
committerDavid Gibson <david@gibson.dropbear.id.au>2021-11-09 10:32:52 +1100
commite06049f38074b9533c4beef37d634dad3bd97c73 (patch)
tree1e5449f1ea9c3cacb6d2c59afdf1a578c5a7f1d6 /include/qemu
parentd39b2cc7d0b87d95bbecbd142179efdc0b85c4e5 (diff)
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host-utils: Introduce mulu128
Signed-off-by: Luis Pires <luis.pires@eldorado.org.br> Reviewed-by: Richard Henderson <richard.henderson@linaro.org> Message-Id: <20211029192417.400707-6-luis.pires@eldorado.org.br> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Diffstat (limited to 'include/qemu')
-rw-r--r--include/qemu/host-utils.h36
1 files changed, 36 insertions, 0 deletions
diff --git a/include/qemu/host-utils.h b/include/qemu/host-utils.h
index a3a7ced7..ca979dc 100644
--- a/include/qemu/host-utils.h
+++ b/include/qemu/host-utils.h
@@ -590,6 +590,42 @@ static inline bool umul64_overflow(uint64_t x, uint64_t y, uint64_t *ret)
#endif
}
+/*
+ * Unsigned 128x64 multiplication.
+ * Returns true if the result got truncated to 128 bits.
+ * Otherwise, returns false and the multiplication result via plow and phigh.
+ */
+static inline bool mulu128(uint64_t *plow, uint64_t *phigh, uint64_t factor)
+{
+#if defined(CONFIG_INT128) && \
+ (__has_builtin(__builtin_mul_overflow) || __GNUC__ >= 5)
+ bool res;
+ __uint128_t r;
+ __uint128_t f = ((__uint128_t)*phigh << 64) | *plow;
+ res = __builtin_mul_overflow(f, factor, &r);
+
+ *plow = r;
+ *phigh = r >> 64;
+
+ return res;
+#else
+ uint64_t dhi = *phigh;
+ uint64_t dlo = *plow;
+ uint64_t ahi;
+ uint64_t blo, bhi;
+
+ if (dhi == 0) {
+ mulu64(plow, phigh, dlo, factor);
+ return false;
+ }
+
+ mulu64(plow, &ahi, dlo, factor);
+ mulu64(&blo, &bhi, dhi, factor);
+
+ return uadd64_overflow(ahi, blo, phigh) || bhi != 0;
+#endif
+}
+
/**
* uadd64_carry - addition with carry-in and carry-out
* @x, @y: addends