1 files changed, 89 insertions, 0 deletions
diff --git a/libgo/runtime/go-memmove.c b/libgo/runtime/go-memmove.c
new file mode 100644
index 0000000..1ca3f48
--- /dev/null
+++ b/libgo/runtime/go-memmove.c
@@ -0,0 +1,89 @@
+/* go-memmove.c -- memmove
+
+   Copyright 2021 The Go Authors. All rights reserved.
+   Use of this source code is governed by a BSD-style
+   license that can be found in the LICENSE file.  */
+
+#include "runtime.h"
+
+void gomemmove(void *, void *, uintptr)
+  __asm__ (GOSYM_PREFIX "runtime.memmove")
+  __attribute__ ((no_split_stack));
+
+// This implementation is necessary since
+// the __builtin_memmove might use __libc_memmove
+// which doesn't require atomicity of 8 byte
+// moves.
+
+void
+gomemmove (void *dst, void *src, uintptr len)
+{
+#if !defined(__PPC64__)
+  __builtin_memmove(dst, src, len);
+#else
+  uint64 offset, tail;
+  int64 rem;
+  uint64 dwords;
+  uint64 i;
+  char *bdst,*bsrc;
+
+  rem = len;
+
+  if (len == 0) {
+	return;
+  }
+
+  // If src and dst don't have the same 8 byte alignment then
+  // there is no issue with copying pointer atomicity. Use the
+  // builtin.
+  if (((uint64)dst % 8) != ((uint64)src % 8) || len < 8) {
+	__builtin_memmove(dst, src, len);
+	return;
+  }
+
+  // Length >= 8 && same ptr alignment
+  offset = (uint64)dst % 8;
+
+  // If not 8 byte alignment, move the intial bytes.
+  if (offset > 0) {
+	__builtin_memmove(dst, src, 8-offset);
+	dst += (8-offset);
+	src += (8-offset);
+	rem -= (8-offset);
+  }
+
+  // Move the tail bytes to make the backward move
+  // easier.
+  tail = rem % 8;
+  if (tail > 0) {
+	__builtin_memmove(dst+rem-tail, src+rem-tail, tail);
+	rem -= tail;
+  }
+
+  if (rem == 0) {
+	return;
+  }
+
+  // Must now be 8 byte alignment and rem is multiple of 8.
+  dwords = len>>3;
+
+  // Determine if a backwards move is needed
+  // Forward or backward, move all doublewords
+
+  if ((uint64)(dst - src) < (uint64)rem) {
+	bdst = dst+rem-8;
+	bsrc = src+rem-8;
+	for (i = 0; i<dwords; i++) {
+		*(uint64*)bdst = *(uint64*)bsrc;
+		bdst -= 8;
+		bsrc -= 8;
+	}
+  } else {
+	for (i = 0; i<dwords; i++) {
+		*(uint64*)dst = *(uint64*)src;
+		dst += 8;
+		src += 8;
+	}
+  }
+#endif
+}