Turn 64-bit integer division and modulus by constants into multiply-high

This trick was already implemented for 32-bit integer division and modulus.  Here we extend it to the 64-bit case.

For 32-bit target processors, the runtime library must implement 64-bit multiply-high (signed and unsigned).  Tentative implementations are provided for IA32 and PowerPC, but need testing.

3 files changed, 124 insertions, 0 deletions

diff --git a/runtime/c/i64.h b/runtime/c/i64.h
index dd584533..a75214fe 100644
--- a/runtime/c/i64.h
+++ b/runtime/c/i64.h
@@ -41,3 +41,5 @@ extern signed long long __i64_sar(signed long long x, int amount);
 extern unsigned long long __i64_udivmod(unsigned long long n,
                                         unsigned long long d,
                                         unsigned long long * rp);
+extern unsigned long long __i64_umulh(unsigned long long u,
+                                      unsigned long long v);
diff --git a/runtime/c/i64_smulh.c b/runtime/c/i64_smulh.c
new file mode 100644
index 00000000..b7a42474
--- /dev/null
+++ b/runtime/c/i64_smulh.c
@@ -0,0 +1,56 @@
+/*****************************************************************
+ *
+ *               The Compcert verified compiler
+ *
+ *           Xavier Leroy, INRIA Paris-Rocquencourt
+ *
+ * Copyright (c) 2013 Institut National de Recherche en Informatique et
+ *  en Automatique.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in the
+ *       documentation and/or other materials provided with the distribution.
+ *     * Neither the name of the <organization> nor the
+ *       names of its contributors may be used to endorse or promote products
+ *       derived from this software without specific prior written permission.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT
+ * HOLDER> BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ **********************************************************************/
+
+/* Helper functions for 64-bit integer arithmetic. Reference C implementation */
+
+#include "i64.h"
+
+typedef signed long long s64;
+typedef unsigned long long u64;
+
+/* Signed multiply high */
+
+/* Hacker's Delight section 8.3:
+ * - compute high 64 bits of the unsigned product X * Y
+ * - subtract X if Y < 0
+ * - subtract Y if X < 0 
+ */
+
+s64 __i64_smulh(s64 x, s64 y)
+{
+  s64 t = (s64) __i64_umulh(x, y);
+  if (y < 0) t = t - x;
+  if (x < 0) t = t - y;
+  return t;
+}
diff --git a/runtime/c/i64_umulh.c b/runtime/c/i64_umulh.c
new file mode 100644
index 00000000..d2394d09
--- /dev/null
+++ b/runtime/c/i64_umulh.c
@@ -0,0 +1,66 @@
+/*****************************************************************
+ *
+ *               The Compcert verified compiler
+ *
+ *           Xavier Leroy, INRIA Paris
+ *
+ * Copyright (c) 2016 Institut National de Recherche en Informatique et
+ *  en Automatique.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in the
+ *       documentation and/or other materials provided with the distribution.
+ *     * Neither the name of the <organization> nor the
+ *       names of its contributors may be used to endorse or promote products
+ *       derived from this software without specific prior written permission.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT
+ * HOLDER> BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ **********************************************************************/
+
+/* Helper functions for 64-bit integer arithmetic. Reference C implementation */
+
+#include "i64.h"
+
+typedef unsigned long long u64;
+typedef unsigned int u32;
+
+/* Unsigned multiply high */
+
+/* Hacker's Delight, algorithm 8.1, specialized to two 32-bit words */
+
+u64 __i64_umulh(u64 u, u64 v)
+{
+  u32 u0 = u, u1 = u >> 32;
+  u32 v0 = v, v1 = v >> 32;
+  u32 w1, w2, w3, k;
+  u64 t;
+
+  t = (u64) u0 * (u64) v0;
+  k = t >> 32;
+
+  t = (u64) u1 * (u64) v0 + k;
+  w1 = t;
+  w2 = t >> 32;
+
+  t = (u64) u0 * (u64) v1 + w1;
+  k = t >> 32;
+
+  t = (u64) u1 * (u64) v1 + w2 + k;
+
+  return t;
+}