diff --git a/mk/rt.mk b/mk/rt.mk
index 77bb22b7bfc69..d0fc577458987 100644
--- a/mk/rt.mk
+++ b/mk/rt.mk
@@ -247,8 +247,8 @@ $$(COMPRT_LIB_$(1)): $$(COMPRT_DEPS) $$(MKFILE_DEPS)
 		RANLIB="$$(AR_$(1)) s" \
 		CFLAGS="$$(CFG_GCCISH_CFLAGS_$(1))" \
 		TargetTriple=$(1) \
-		triple-runtime
-	$$(Q)cp $$(COMPRT_BUILD_DIR_$(1))/triple/runtime/libcompiler_rt.a $$(COMPRT_LIB_$(1))
+		triple-builtins
+	$$(Q)cp $$(COMPRT_BUILD_DIR_$(1))/triple/builtins/libcompiler_rt.a $$(COMPRT_LIB_$(1))
 
 ################################################################################
 # libbacktrace
diff --git a/src/compiler-rt b/src/compiler-rt
index f4b221571ce6f..ed112ca1e4275 160000
--- a/src/compiler-rt
+++ b/src/compiler-rt
@@ -1 +1 @@
-Subproject commit f4b221571ce6f05714c1f1c6fa48f1393499989c
+Subproject commit ed112ca1e4275e1c5707a898f2bf6164707ba378
diff --git a/src/etc/get-snapshot.py b/src/etc/get-snapshot.py
index fd97affd9ad58..faa21ca74df09 100755
--- a/src/etc/get-snapshot.py
+++ b/src/etc/get-snapshot.py
@@ -50,7 +50,9 @@ def unpack_snapshot(triple, dl_path):
 if len(sys.argv) == 3:
   dl_path = sys.argv[2]
 else:
-  snap = determine_curr_snapshot(triple)
+  # There are no 64-bit Windows snapshots yet, so we'll use 32-bit ones instead, for now
+  snap_triple = triple if triple != "x86_64-w64-mingw32" else "i686-pc-mingw32"
+  snap = determine_curr_snapshot(snap_triple)
   dl = os.path.join(download_dir_base, snap)
   url = download_url_base + "/" + snap
   print("determined most recent snapshot: " + snap)
diff --git a/src/libgreen/macros.rs b/src/libgreen/macros.rs
index d1d7a9e0c98da..34e29b06f76cc 100644
--- a/src/libgreen/macros.rs
+++ b/src/libgreen/macros.rs
@@ -52,20 +52,9 @@ macro_rules! rtabort (
 
 pub fn dumb_println(args: &fmt::Arguments) {
     use std::io;
-    use libc;
+    use std::rt;
 
-    struct Stderr;
-    impl io::Writer for Stderr {
-        fn write(&mut self, data: &[u8]) -> io::IoResult<()> {
-            unsafe {
-                libc::write(libc::STDERR_FILENO,
-                            data.as_ptr() as *libc::c_void,
-                            data.len() as libc::size_t);
-            }
-            Ok(()) // just ignore the result
-        }
-    }
-    let mut w = Stderr;
+    let mut w = rt::Stderr;
     let _ = fmt::writeln(&mut w as &mut io::Writer, args);
 }
 
diff --git a/src/librustuv/macros.rs b/src/librustuv/macros.rs
index df41adfafbece..8e827703cb2b8 100644
--- a/src/librustuv/macros.rs
+++ b/src/librustuv/macros.rs
@@ -29,19 +29,8 @@ macro_rules! uvdebug (
 
 pub fn dumb_println(args: &fmt::Arguments) {
     use std::io;
-    use libc;
+    use std::rt;
 
-    struct Stderr;
-    impl io::Writer for Stderr {
-        fn write(&mut self, data: &[u8]) -> io::IoResult<()> {
-            let _ = unsafe {
-                libc::write(libc::STDERR_FILENO,
-                            data.as_ptr() as *libc::c_void,
-                            data.len() as libc::size_t)
-            };
-            Ok(()) // just ignore the errors
-        }
-    }
-    let mut w = Stderr;
+    let mut w = rt::Stderr;
     let _ = fmt::writeln(&mut w as &mut io::Writer, args);
 }
diff --git a/src/libstd/io/stdio.rs b/src/libstd/io/stdio.rs
index 96439439e7aef..afef21e7c688f 100644
--- a/src/libstd/io/stdio.rs
+++ b/src/libstd/io/stdio.rs
@@ -27,7 +27,6 @@ out.write(bytes!("Hello, world!"));
 
 */
 
-use container::Container;
 use fmt;
 use io::{Reader, Writer, IoResult, IoError, OtherIoError,
          standard_error, EndOfFile, LineBufferedWriter, BufferedReader};
@@ -37,11 +36,11 @@ use mem::replace;
 use option::{Option, Some, None};
 use prelude::drop;
 use result::{Ok, Err};
+use rt;
 use rt::local::Local;
 use rt::rtio::{DontClose, IoFactory, LocalIo, RtioFileStream, RtioTTY};
 use rt::task::Task;
 use str::StrSlice;
-use slice::ImmutableVector;
 
 // And so begins the tale of acquiring a uv handle to a stdio stream on all
 // platforms in all situations. Our story begins by splitting the world into two
@@ -236,18 +235,7 @@ fn with_task_stdout(f: |&mut Writer| -> IoResult<()> ) {
         }
 
         None => {
-            struct Stdout;
-            impl Writer for Stdout {
-                fn write(&mut self, data: &[u8]) -> IoResult<()> {
-                    unsafe {
-                        libc::write(libc::STDOUT_FILENO,
-                                    data.as_ptr() as *libc::c_void,
-                                    data.len() as libc::size_t);
-                    }
-                    Ok(()) // just ignore the results
-                }
-            }
-            let mut io = Stdout;
+            let mut io = rt::Stdout;
             f(&mut io as &mut Writer)
         }
     };
diff --git a/src/libstd/rt/backtrace.rs b/src/libstd/rt/backtrace.rs
index c3bf7a6d12a67..85699cdfebc02 100644
--- a/src/libstd/rt/backtrace.rs
+++ b/src/libstd/rt/backtrace.rs
@@ -665,6 +665,89 @@ mod imp {
         }
     }
 
+    #[cfg(target_arch = "x86_64")]
+    mod arch {
+        use libc::{c_longlong, c_ulonglong};
+        use libc::types::os::arch::extra::{WORD, DWORD, DWORDLONG};
+
+        pub struct CONTEXT {
+            P1Home: DWORDLONG,
+            P2Home: DWORDLONG,
+            P3Home: DWORDLONG,
+            P4Home: DWORDLONG,
+            P5Home: DWORDLONG,
+            P6Home: DWORDLONG,
+
+            ContextFlags: DWORD,
+            MxCsr: DWORD,
+
+            SegCs: WORD,
+            SegDs: WORD,
+            SegEs: WORD,
+            SegFs: WORD,
+            SegGs: WORD,
+            SegSs: WORD,
+            EFlags: DWORD,
+
+            Dr0: DWORDLONG,
+            Dr1: DWORDLONG,
+            Dr2: DWORDLONG,
+            Dr3: DWORDLONG,
+            Dr6: DWORDLONG,
+            Dr7: DWORDLONG,
+
+            Rax: DWORDLONG,
+            Rcx: DWORDLONG,
+            Rdx: DWORDLONG,
+            Rbx: DWORDLONG,
+            Rsp: DWORDLONG,
+            Rbp: DWORDLONG,
+            Rsi: DWORDLONG,
+            Rdi: DWORDLONG,
+            R8:  DWORDLONG,
+            R9:  DWORDLONG,
+            R10: DWORDLONG,
+            R11: DWORDLONG,
+            R12: DWORDLONG,
+            R13: DWORDLONG,
+            R14: DWORDLONG,
+            R15: DWORDLONG,
+
+            Rip: DWORDLONG,
+
+            FltSave: FLOATING_SAVE_AREA,
+
+            VectorRegister: [M128A, .. 26],
+            VectorControl: DWORDLONG,
+
+            DebugControl: DWORDLONG,
+            LastBranchToRip: DWORDLONG,
+            LastBranchFromRip: DWORDLONG,
+            LastExceptionToRip: DWORDLONG,
+            LastExceptionFromRip: DWORDLONG,
+        }
+
+        pub struct M128A {
+            Low:  c_ulonglong,
+            High: c_longlong
+        }
+
+        pub struct FLOATING_SAVE_AREA {
+            _Dummy: [u8, ..512] // FIXME: Fill this out
+        }
+
+        pub fn init_frame(frame: &mut super::STACKFRAME64,
+                          ctx: &CONTEXT) -> DWORD {
+            frame.AddrPC.Offset = ctx.Rip as u64;
+            frame.AddrPC.Mode = super::AddrModeFlat;
+            frame.AddrStack.Offset = ctx.Rsp as u64;
+            frame.AddrStack.Mode = super::AddrModeFlat;
+            frame.AddrFrame.Offset = ctx.Rbp as u64;
+            frame.AddrFrame.Mode = super::AddrModeFlat;
+            super::IMAGE_FILE_MACHINE_AMD64
+        }
+    }
+
     struct Cleanup {
         handle: libc::HANDLE,
         SymCleanup: SymCleanupFn,
diff --git a/src/libstd/rt/mod.rs b/src/libstd/rt/mod.rs
index f4a4fd9ab2e9b..a61443d335acb 100644
--- a/src/libstd/rt/mod.rs
+++ b/src/libstd/rt/mod.rs
@@ -71,6 +71,8 @@ pub use self::util::default_sched_threads;
 // Export unwinding facilities used by the failure macros
 pub use self::unwind::{begin_unwind, begin_unwind_raw, begin_unwind_fmt};
 
+pub use self::util::{Stdio, Stdout, Stderr};
+
 // FIXME: these probably shouldn't be public...
 #[doc(hidden)]
 pub mod shouldnt_be_public {
diff --git a/src/libstd/rt/util.rs b/src/libstd/rt/util.rs
index 4c208a64ddfcc..84284ca1faf52 100644
--- a/src/libstd/rt/util.rs
+++ b/src/libstd/rt/util.rs
@@ -71,14 +71,22 @@ pub fn default_sched_threads() -> uint {
     }
 }
 
-pub struct Stderr;
+pub struct Stdio(libc::c_int);
 
-impl io::Writer for Stderr {
+pub static Stdout: Stdio = Stdio(libc::STDOUT_FILENO);
+pub static Stderr: Stdio = Stdio(libc::STDERR_FILENO);
+
+impl io::Writer for Stdio {
     fn write(&mut self, data: &[u8]) -> IoResult<()> {
+        #[cfg(unix)]
+        type WriteLen = libc::size_t;
+        #[cfg(windows)]
+        type WriteLen = libc::c_uint;
         unsafe {
-            libc::write(libc::STDERR_FILENO,
+            let Stdio(fd) = *self;
+            libc::write(fd,
                         data.as_ptr() as *libc::c_void,
-                        data.len() as libc::size_t);
+                        data.len() as WriteLen);
         }
         Ok(()) // yes, we're lying
     }
diff --git a/src/libstd/unstable/mutex.rs b/src/libstd/unstable/mutex.rs
index c2db8ad9586ee..8faedcbd9edf9 100644
--- a/src/libstd/unstable/mutex.rs
+++ b/src/libstd/unstable/mutex.rs
@@ -444,6 +444,8 @@ mod imp {
     static SPIN_COUNT: DWORD = 4000;
     #[cfg(target_arch = "x86")]
     static CRIT_SECTION_SIZE: uint = 24;
+    #[cfg(target_arch = "x86_64")]
+    static CRIT_SECTION_SIZE: uint = 40;
 
     pub struct Mutex {
         // pointers for the lock/cond handles, atomically updated