host-utils: move udiv_qrnnd() to host-utils

Move udiv_qrnnd() from include/fpu/softfloat-macros.h to host-utils,
so it can be reused by divu128().

Signed-off-by: Luis Pires <luis.pires@eldorado.org.br>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20211025191154.350831-3-luis.pires@eldorado.org.br>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

1 files changed, 81 insertions, 0 deletions

diff --git a/include/qemu/host-utils.h b/include/qemu/host-utils.h
index e82e623..08a17e1 100644
--- a/include/qemu/host-utils.h
+++ b/include/qemu/host-utils.h
@@ -23,6 +23,10 @@
  * THE SOFTWARE.
  */
 
+/* Portions of this work are licensed under the terms of the GNU GPL,
+ * version 2 or later. See the COPYING file in the top-level directory.
+ */
+
 #ifndef HOST_UTILS_H
 #define HOST_UTILS_H
 
@@ -726,4 +730,81 @@ void urshift(uint64_t *plow, uint64_t *phigh, int32_t shift);
  */
 void ulshift(uint64_t *plow, uint64_t *phigh, int32_t shift, bool *overflow);
 
+/* From the GNU Multi Precision Library - longlong.h __udiv_qrnnd
+ * (https://gmplib.org/repo/gmp/file/tip/longlong.h)
+ *
+ * Licensed under the GPLv2/LGPLv3
+ */
+static inline uint64_t udiv_qrnnd(uint64_t *r, uint64_t n1,
+                                  uint64_t n0, uint64_t d)
+{
+#if defined(__x86_64__)
+    uint64_t q;
+    asm("divq %4" : "=a"(q), "=d"(*r) : "0"(n0), "1"(n1), "rm"(d));
+    return q;
+#elif defined(__s390x__) && !defined(__clang__)
+    /* Need to use a TImode type to get an even register pair for DLGR.  */
+    unsigned __int128 n = (unsigned __int128)n1 << 64 | n0;
+    asm("dlgr %0, %1" : "+r"(n) : "r"(d));
+    *r = n >> 64;
+    return n;
+#elif defined(_ARCH_PPC64) && defined(_ARCH_PWR7)
+    /* From Power ISA 2.06, programming note for divdeu.  */
+    uint64_t q1, q2, Q, r1, r2, R;
+    asm("divdeu %0,%2,%4; divdu %1,%3,%4"
+        : "=&r"(q1), "=r"(q2)
+        : "r"(n1), "r"(n0), "r"(d));
+    r1 = -(q1 * d);         /* low part of (n1<<64) - (q1 * d) */
+    r2 = n0 - (q2 * d);
+    Q = q1 + q2;
+    R = r1 + r2;
+    if (R >= d || R < r2) { /* overflow implies R > d */
+        Q += 1;
+        R -= d;
+    }
+    *r = R;
+    return Q;
+#else
+    uint64_t d0, d1, q0, q1, r1, r0, m;
+
+    d0 = (uint32_t)d;
+    d1 = d >> 32;
+
+    r1 = n1 % d1;
+    q1 = n1 / d1;
+    m = q1 * d0;
+    r1 = (r1 << 32) | (n0 >> 32);
+    if (r1 < m) {
+        q1 -= 1;
+        r1 += d;
+        if (r1 >= d) {
+            if (r1 < m) {
+                q1 -= 1;
+                r1 += d;
+            }
+        }
+    }
+    r1 -= m;
+
+    r0 = r1 % d1;
+    q0 = r1 / d1;
+    m = q0 * d0;
+    r0 = (r0 << 32) | (uint32_t)n0;
+    if (r0 < m) {
+        q0 -= 1;
+        r0 += d;
+        if (r0 >= d) {
+            if (r0 < m) {
+                q0 -= 1;
+                r0 += d;
+            }
+        }
+    }
+    r0 -= m;
+
+    *r = r0;
+    return (q1 << 32) | q0;
+#endif
+}
+
 #endif