Addition of div and rem on 128-bit integers, using the 128/64->128 divu and
64x64->128 mulu in host-utils.
These operations will be used within div/rem helpers in the 128-bit riscv
target.
Signed-off-by: Frédéric Pétrot
Co-authored-by: Fabien Portas
Reviewed-by: Alistair Francis
---
include/qemu/int128.h | 6 ++
util/int128.c | 145 ++
util/meson.build | 1 +
3 files changed, 152 insertions(+)
create mode 100644 util/int128.c
diff --git a/include/qemu/int128.h b/include/qemu/int128.h
index b6d517aea4..ef41892dac 100644
--- a/include/qemu/int128.h
+++ b/include/qemu/int128.h
@@ -386,4 +386,10 @@ static inline void bswap128s(Int128 *s)
*s = bswap128(*s);
}
+#define UINT128_MAX int128_make128(~0LL, ~0LL)
+Int128 int128_divu(Int128, Int128);
+Int128 int128_remu(Int128, Int128);
+Int128 int128_divs(Int128, Int128);
+Int128 int128_rems(Int128, Int128);
+
#endif /* INT128_H */
diff --git a/util/int128.c b/util/int128.c
new file mode 100644
index 00..62c56c8b7c
--- /dev/null
+++ b/util/int128.c
@@ -0,0 +1,145 @@
+#include "qemu/osdep.h"
+#include "qemu/host-utils.h"
+#include "qemu/int128.h"
+
+#ifdef CONFIG_INT128
+
+Int128 int128_divu(Int128 a, Int128 b)
+{
+return (__uint128_t)a / (__uint128_t)b;
+}
+
+Int128 int128_remu(Int128 a, Int128 b)
+{
+return (__uint128_t)a % (__uint128_t)b;
+}
+
+Int128 int128_divs(Int128 a, Int128 b)
+{
+return a / b;
+}
+
+Int128 int128_rems(Int128 a, Int128 b)
+{
+return a % b;
+}
+
+#else
+
+/*
+ * Division and remainder algorithms for 128-bit due to Stefan Kanthak,
+ * https://skanthak.homepage.t-online.de/integer.html#udivmodti4
+ * Preconditions:
+ * - function should never be called with v equals to 0, it has to
+ * be dealt with beforehand
+ * - quotien pointer must be valid
+ */
+static Int128 divrem128(Int128 u, Int128 v, Int128 *q)
+{
+Int128 qq;
+uint64_t hi, lo, tmp;
+int s = clz64(v.hi);
+
+if (s == 64) {
+/* we have uu÷0v => let's use divu128 */
+hi = u.hi;
+lo = u.lo;
+tmp = divu128(, , v.lo);
+*q = int128_make128(lo, hi);
+return int128_make128(tmp, 0);
+} else {
+hi = int128_gethi(int128_lshift(v, s));
+
+if (hi > u.hi) {
+lo = u.lo;
+tmp = u.hi;
+divu128(, , hi);
+lo = int128_gethi(int128_lshift(int128_make128(lo, 0), s));
+} else { /* prevent overflow */
+lo = u.lo;
+tmp = u.hi - hi;
+divu128(, , hi);
+lo = int128_gethi(int128_lshift(int128_make128(lo, 1), s));
+}
+
+qq = int128_make64(lo);
+
+tmp = lo * v.hi;
+mulu64(, , lo, v.lo);
+hi += tmp;
+
+if (hi < tmp /* quotient * divisor >= 2**128 > dividend */
+|| hi > u.hi /* quotient * divisor > dividend */
+|| (hi == u.hi && lo > u.lo)) {
+qq.lo -= 1;
+mulu64(, , qq.lo, v.lo);
+hi += qq.lo * v.hi;
+}
+
+*q = qq;
+u.hi -= hi + (u.lo < lo);
+u.lo -= lo;
+return u;
+}
+}
+
+Int128 int128_divu(Int128 a, Int128 b)
+{
+Int128 q;
+divrem128(a, b, );
+return q;
+}
+
+Int128 int128_remu(Int128 a, Int128 b)
+{
+Int128 q;
+return divrem128(a, b, );
+}
+
+Int128 int128_divs(Int128 a, Int128 b)
+{
+Int128 q;
+bool sgna = !int128_nonneg(a);
+bool sgnb = !int128_nonneg(b);
+
+if (sgna) {
+a = int128_neg(a);
+}
+
+if (sgnb) {
+b = int128_neg(b);
+}
+
+divrem128(a, b, );
+
+if (sgna != sgnb) {
+q = int128_neg(q);
+}
+
+return q;
+}
+
+Int128 int128_rems(Int128 a, Int128 b)
+{
+Int128 q, r;
+bool sgna = !int128_nonneg(a);
+bool sgnb = !int128_nonneg(b);
+
+if (sgna) {
+a = int128_neg(a);
+}
+
+if (sgnb) {
+b = int128_neg(b);
+}
+
+r = divrem128(a, b, );
+
+if (sgna) {
+r = int128_neg(r);
+}
+
+return r;
+}
+
+#endif
diff --git a/util/meson.build b/util/meson.build
index 05b593055a..e676b2f6c6 100644
--- a/util/meson.build
+++ b/util/meson.build
@@ -48,6 +48,7 @@ util_ss.add(files('transactions.c'))
util_ss.add(when: 'CONFIG_POSIX', if_true: files('drm.c'))
util_ss.add(files('guest-random.c'))
util_ss.add(files('yank.c'))
+util_ss.add(files('int128.c'))
if have_user
util_ss.add(files('selfmap.c'))
--
2.34.0
