Sema: `@memcpy` changes

* The langspec definition of `@memcpy` has been changed so that the
  source and destination element types must be in-memory coercible,
  allowing all such calls to be raw copying operations, not actually
  applying any coercions.
* Implement aliasing check for comptime `@memcpy`; a compile error will
  now be emitted if the arguments alias.
* Implement more efficient comptime `@memcpy` by loading and storing a
  whole array at once, similar to how `@memset` is implemented.

1 files changed, 14 insertions, 0 deletions

diff --git a/test/cases/compile_errors/memcpy_alias.zig b/test/cases/compile_errors/memcpy_alias.zig
new file mode 100644
index 0000000000..3f6a5653e8
--- /dev/null
+++ b/test/cases/compile_errors/memcpy_alias.zig
@@ -0,0 +1,14 @@
+var arr: [10]u64 = undefined;
+export fn foo() void {
+    @memcpy(arr[0..6], arr[4..10]);
+}
+
+comptime {
+    var types: [4]type = .{ u8, u16, u32, u64 };
+    @memcpy(types[2..4], types[1..3]);
+}
+
+// error
+//
+// :3:5: error: '@memcpy' arguments alias
+// :8:5: error: '@memcpy' arguments alias