1 files changed, 74 insertions, 0 deletions
diff --git a/third_party/bearssl/src/i31_mulacc.c b/third_party/bearssl/src/i31_mulacc.c
new file mode 100644
index 0000000..7410e54
--- /dev/null
+++ b/third_party/bearssl/src/i31_mulacc.c
@@ -0,0 +1,74 @@
+/*
+ * Copyright (c) 2016 Thomas Pornin <[email protected]>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining 
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be 
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "inner.h"
+
+/* see inner.h */
+void
+br_i31_mulacc(uint32_t *d, const uint32_t *a, const uint32_t *b)
+{
+	size_t alen, blen, u;
+	uint32_t dl, dh;
+
+	alen = (a[0] + 31) >> 5;
+	blen = (b[0] + 31) >> 5;
+
+	/*
+	 * We want to add the two bit lengths, but these are encoded,
+	 * which requires some extra care.
+	 */
+	dl = (a[0] & 31) + (b[0] & 31);
+	dh = (a[0] >> 5) + (b[0] >> 5);
+	d[0] = (dh << 5) + dl + (~(uint32_t)(dl - 31) >> 31);
+
+	for (u = 0; u < blen; u ++) {
+		uint32_t f;
+		size_t v;
+
+		/*
+		 * Carry always fits on 31 bits; we want to keep it in a
+		 * 32-bit register on 32-bit architectures (on a 64-bit
+		 * architecture, cast down from 64 to 32 bits means
+		 * clearing the high bits, which is not free; on a 32-bit
+		 * architecture, the same operation really means ignoring
+		 * the top register, which has negative or zero cost).
+		 */
+#if BR_64
+		uint64_t cc;
+#else
+		uint32_t cc;
+#endif
+
+		f = b[1 + u];
+		cc = 0;
+		for (v = 0; v < alen; v ++) {
+			uint64_t z;
+
+			z = (uint64_t)d[1 + u + v] + MUL31(f, a[1 + v]) + cc;
+			cc = z >> 31;
+			d[1 + u + v] = (uint32_t)z & 0x7FFFFFFF;
+		}
+		d[1 + u + alen] = (uint32_t)cc;
+	}
+}