[Qemu-devel] [PATCH v2 4/4] softfloat: Specialize udiv_qrnnd for ppc64

[Richard Henderson <richard.henderson@linaro.org>]

The ISA has a 128/64-bit division instruction, though it assumes the
low 64-bits of the numerator are 0, and so requires a bit more fixup
than a full 128-bit division insn.

Cc: qemu-ppc@nongnu.org
Cc: Alexander Graf <agraf@suse.de>
Cc: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 include/fpu/softfloat-macros.h | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/include/fpu/softfloat-macros.h b/include/fpu/softfloat-macros.h
index e702607b43..001bf4f23c 100644
--- a/include/fpu/softfloat-macros.h
+++ b/include/fpu/softfloat-macros.h
@@ -632,6 +632,22 @@ static inline uint64_t udiv_qrnnd(uint64_t *r, uint64_t n1,
     asm("dlgr %0, %1" : "+r"(n) : "r"(d));
     *r = n >> 64;
     return n;
+#elif defined(_ARCH_PPC64)
+    /* From Power ISA 3.0B, 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 = r2 + r1;
+    if (R < r2 || R >= d) { /* overflow implies R > d */
+        Q += 1;
+        R -= d;
+    }
+    *r = R;
+    return Q;
 #else
     uint64_t d0, d1, q0, q1, r1, r0, m;
 
-- 
2.17.1