diff --git a/src/test/run-pass/atomic-print.rs b/src/test/run-pass/atomic-print.rs
index aa1ef2025a015..ebc9f80193119 100644
--- a/src/test/run-pass/atomic-print.rs
+++ b/src/test/run-pass/atomic-print.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 use std::{env, fmt, process, sync, thread};
 
 struct SlowFmt(u32);
diff --git a/src/test/run-pass/box-of-array-of-drop-1.rs b/src/test/run-pass/box-of-array-of-drop-1.rs
index e889d74c7ccc4..a63a232e1b5be 100644
--- a/src/test/run-pass/box-of-array-of-drop-1.rs
+++ b/src/test/run-pass/box-of-array-of-drop-1.rs
@@ -11,6 +11,8 @@
 // Test that we cleanup a fixed size Box<[D; k]> properly when D has a
 // destructor.
 
+// ignore-emscripten no threads support
+
 #![feature(const_fn)]
 
 use std::thread;
diff --git a/src/test/run-pass/box-of-array-of-drop-2.rs b/src/test/run-pass/box-of-array-of-drop-2.rs
index f108ef4f5d22d..ca17942917281 100644
--- a/src/test/run-pass/box-of-array-of-drop-2.rs
+++ b/src/test/run-pass/box-of-array-of-drop-2.rs
@@ -11,6 +11,8 @@
 // Test that we cleanup dynamic sized Box<[D]> properly when D has a
 // destructor.
 
+// ignore-emscripten no threads support
+
 #![feature(const_fn)]
 
 use std::thread;
diff --git a/src/test/run-pass/cci_capture_clause.rs b/src/test/run-pass/cci_capture_clause.rs
index 80b75af6e441e..5019455c2a7f0 100644
--- a/src/test/run-pass/cci_capture_clause.rs
+++ b/src/test/run-pass/cci_capture_clause.rs
@@ -14,6 +14,7 @@
 // that use capture clauses.
 
 // pretty-expanded FIXME #23616
+// ignore-emscripten no threads support
 
 extern crate cci_capture_clause;
 
diff --git a/src/test/run-pass/child-outlives-parent.rs b/src/test/run-pass/child-outlives-parent.rs
index 7da1416602f6d..e45f7c2bba668 100644
--- a/src/test/run-pass/child-outlives-parent.rs
+++ b/src/test/run-pass/child-outlives-parent.rs
@@ -11,6 +11,7 @@
 // Reported as issue #126, child leaks the string.
 
 // pretty-expanded FIXME #23616
+// ignore-emscripten no threads support
 
 #![feature(std_misc)]
 
diff --git a/src/test/run-pass/cleanup-rvalue-temp-during-incomplete-alloc.rs b/src/test/run-pass/cleanup-rvalue-temp-during-incomplete-alloc.rs
index 344ea63c7c74d..25d3eb3bbe28c 100644
--- a/src/test/run-pass/cleanup-rvalue-temp-during-incomplete-alloc.rs
+++ b/src/test/run-pass/cleanup-rvalue-temp-during-incomplete-alloc.rs
@@ -24,6 +24,7 @@
 // It's unclear how likely such a bug is to recur, but it seems like a
 // scenario worth testing.
 
+// ignore-emscripten no threads support
 
 #![allow(unknown_features)]
 #![feature(box_syntax)]
diff --git a/src/test/run-pass/clone-with-exterior.rs b/src/test/run-pass/clone-with-exterior.rs
index 5a7b1c83dfda3..384fb92954de2 100644
--- a/src/test/run-pass/clone-with-exterior.rs
+++ b/src/test/run-pass/clone-with-exterior.rs
@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
 
 #![allow(unknown_features)]
 #![feature(box_syntax, std_misc)]
diff --git a/src/test/run-pass/comm.rs b/src/test/run-pass/comm.rs
index 72f623ccfde7a..d7cb8bc991ada 100644
--- a/src/test/run-pass/comm.rs
+++ b/src/test/run-pass/comm.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 #![feature(std_misc)]
 
 use std::thread;
diff --git a/src/test/run-pass/core-run-destroy.rs b/src/test/run-pass/core-run-destroy.rs
index d6b6d673ca543..ffcc1891c579e 100644
--- a/src/test/run-pass/core-run-destroy.rs
+++ b/src/test/run-pass/core-run-destroy.rs
@@ -10,6 +10,7 @@
 
 // ignore-pretty
 // compile-flags:--test
+// ignore-emscripten
 
 // NB: These tests kill child processes. Valgrind sees these children as leaking
 // memory, which makes for some *confusing* logs. That's why these are here
diff --git a/src/test/run-pass/drop-flag-skip-sanity-check.rs b/src/test/run-pass/drop-flag-skip-sanity-check.rs
index 4a6c8ce70dcee..07a10c8d45443 100644
--- a/src/test/run-pass/drop-flag-skip-sanity-check.rs
+++ b/src/test/run-pass/drop-flag-skip-sanity-check.rs
@@ -9,6 +9,7 @@
 // except according to those terms.
 
 // compile-flags: -Z force-dropflag-checks=off
+// ignore-emscripten no threads support
 
 // Quick-and-dirty test to ensure -Z force-dropflag-checks=off works as
 // expected. Note that the inlined drop-flag is slated for removal
diff --git a/src/test/run-pass/extern-call-deep2.rs b/src/test/run-pass/extern-call-deep2.rs
index 252086ad014da..1a0191b70530a 100644
--- a/src/test/run-pass/extern-call-deep2.rs
+++ b/src/test/run-pass/extern-call-deep2.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 #![feature(libc)]
 
 extern crate libc;
diff --git a/src/test/run-pass/extern-call-scrub.rs b/src/test/run-pass/extern-call-scrub.rs
index 9a39b1773e533..1beb6d3519aee 100644
--- a/src/test/run-pass/extern-call-scrub.rs
+++ b/src/test/run-pass/extern-call-scrub.rs
@@ -12,6 +12,8 @@
 // make sure the stack pointers are maintained properly in both
 // directions
 
+// ignore-emscripten no threads support
+
 #![feature(libc, std_misc)]
 
 extern crate libc;
diff --git a/src/test/run-pass/fds-are-cloexec.rs b/src/test/run-pass/fds-are-cloexec.rs
index 3c7d2861c877e..c2916ccd75b8e 100644
--- a/src/test/run-pass/fds-are-cloexec.rs
+++ b/src/test/run-pass/fds-are-cloexec.rs
@@ -10,6 +10,7 @@
 
 // ignore-windows
 // ignore-android
+// ignore-emscripten
 
 #![feature(libc)]
 
diff --git a/src/test/run-pass/foreign-call-no-runtime.rs b/src/test/run-pass/foreign-call-no-runtime.rs
index f4792c212165d..ca118899798b8 100644
--- a/src/test/run-pass/foreign-call-no-runtime.rs
+++ b/src/test/run-pass/foreign-call-no-runtime.rs
@@ -9,6 +9,8 @@
 // except according to those terms.
 
 // ignore-aarch64
+// ignore-emscripten no threads support
+
 #![feature(libc)]
 
 extern crate libc;
diff --git a/src/test/run-pass/init-large-type.rs b/src/test/run-pass/init-large-type.rs
index dafa8ee10339e..2ff024a693aae 100644
--- a/src/test/run-pass/init-large-type.rs
+++ b/src/test/run-pass/init-large-type.rs
@@ -13,6 +13,7 @@
 // optimisation.
 
 // pretty-expanded FIXME #23616
+// ignore-emscripten no threads support
 
 #![feature(intrinsics, std_misc)]
 
diff --git a/src/test/run-pass/int-abs-overflow.rs b/src/test/run-pass/int-abs-overflow.rs
index 3f50a7d6c0298..e17e3a16d6834 100644
--- a/src/test/run-pass/int-abs-overflow.rs
+++ b/src/test/run-pass/int-abs-overflow.rs
@@ -9,6 +9,7 @@
 // except according to those terms.
 
 // compile-flags: -Z force-overflow-checks=on
+// ignore-emscripten no threads support
 
 use std::thread;
 
diff --git a/src/test/run-pass/intrinsic-move-val-cleanups.rs b/src/test/run-pass/intrinsic-move-val-cleanups.rs
index 9fd4f2133b70d..8f22579423fd5 100644
--- a/src/test/run-pass/intrinsic-move-val-cleanups.rs
+++ b/src/test/run-pass/intrinsic-move-val-cleanups.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 // This test is checking that the move_val_init intrinsic is
 // respecting cleanups for both of its argument expressions.
 //
diff --git a/src/test/run-pass/issue-13494.rs b/src/test/run-pass/issue-13494.rs
index e94368925abee..316190b54eb08 100644
--- a/src/test/run-pass/issue-13494.rs
+++ b/src/test/run-pass/issue-13494.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 // This test may not always fail, but it can be flaky if the race it used to
 // expose is still present.
 
diff --git a/src/test/run-pass/issue-16560.rs b/src/test/run-pass/issue-16560.rs
index a9f7d86f95ee6..596f0d20155df 100644
--- a/src/test/run-pass/issue-16560.rs
+++ b/src/test/run-pass/issue-16560.rs
@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
 
 #![feature(unboxed_closures)]
 
diff --git a/src/test/run-pass/issue-16671.rs b/src/test/run-pass/issue-16671.rs
index 1ebe3a7f068ac..2be04551cb92f 100644
--- a/src/test/run-pass/issue-16671.rs
+++ b/src/test/run-pass/issue-16671.rs
@@ -11,6 +11,8 @@
 // DON'T REENABLE THIS UNLESS YOU'VE ACTUALLY FIXED THE UNDERLYING ISSUE
 // ignore-android seems to block forever
 
+// ignore-emscripten no threads support
+
 #![forbid(warnings)]
 
 // Pretty printing tests complain about `use std::predule::*`
diff --git a/src/test/run-pass/issue-21291.rs b/src/test/run-pass/issue-21291.rs
index ec095d4895ff4..6b45a4d0a5207 100644
--- a/src/test/run-pass/issue-21291.rs
+++ b/src/test/run-pass/issue-21291.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 // Regression test for unwrapping the result of `join`, issue #21291
 
 use std::thread;
diff --git a/src/test/run-pass/issue-22864-2.rs b/src/test/run-pass/issue-22864-2.rs
index da78578329b73..f9360af011bc9 100644
--- a/src/test/run-pass/issue-22864-2.rs
+++ b/src/test/run-pass/issue-22864-2.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 pub fn main() {
     let f = || || 0;
     std::thread::spawn(f());
diff --git a/src/test/run-pass/issue-25089.rs b/src/test/run-pass/issue-25089.rs
index b619d1dd4488c..e707023530be8 100644
--- a/src/test/run-pass/issue-25089.rs
+++ b/src/test/run-pass/issue-25089.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 use std::thread;
 
 struct Foo(i32);
diff --git a/src/test/run-pass/issue-26655.rs b/src/test/run-pass/issue-26655.rs
index bdd3a80d74cf4..402460e7253d3 100644
--- a/src/test/run-pass/issue-26655.rs
+++ b/src/test/run-pass/issue-26655.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 #![feature(const_fn)]
 
 // Check that the destructors of simple enums are run on unwinding
diff --git a/src/test/run-pass/issue-29488.rs b/src/test/run-pass/issue-29488.rs
index eee0f663df24c..17a6e9bd6b2e7 100644
--- a/src/test/run-pass/issue-29488.rs
+++ b/src/test/run-pass/issue-29488.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 use std::thread;
 
 struct Foo;
diff --git a/src/test/run-pass/issue-30018-panic.rs b/src/test/run-pass/issue-30018-panic.rs
index da4d5f19d4a2e..e39ffb87425dc 100644
--- a/src/test/run-pass/issue-30018-panic.rs
+++ b/src/test/run-pass/issue-30018-panic.rs
@@ -13,6 +13,8 @@
 // spawned thread to isolate the expected error result from the
 // SIGTRAP injected by the drop-flag consistency checking.
 
+// ignore-emscripten no threads support
+
 struct Foo;
 
 impl Drop for Foo {
diff --git a/src/test/run-pass/issue-4446.rs b/src/test/run-pass/issue-4446.rs
index 9292a9c608eb9..5eec800d58846 100644
--- a/src/test/run-pass/issue-4446.rs
+++ b/src/test/run-pass/issue-4446.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 use std::sync::mpsc::channel;
 use std::thread;
 
diff --git a/src/test/run-pass/issue-4448.rs b/src/test/run-pass/issue-4448.rs
index eb411ff441778..6f0356b5bfbc8 100644
--- a/src/test/run-pass/issue-4448.rs
+++ b/src/test/run-pass/issue-4448.rs
@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
 
 use std::sync::mpsc::channel;
 use std::thread;
diff --git a/src/test/run-pass/issue-8460.rs b/src/test/run-pass/issue-8460.rs
index 4ebc43163ede8..8ec9f8aff8ec7 100644
--- a/src/test/run-pass/issue-8460.rs
+++ b/src/test/run-pass/issue-8460.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 #![feature(zero_one)]
 
 use std::num::Zero;
diff --git a/src/test/run-pass/issue-8827.rs b/src/test/run-pass/issue-8827.rs
index 280311af6fbd1..6e01131cfcaa4 100644
--- a/src/test/run-pass/issue-8827.rs
+++ b/src/test/run-pass/issue-8827.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 #![feature(std_misc)]
 
 use std::thread;
diff --git a/src/test/run-pass/issue-9396.rs b/src/test/run-pass/issue-9396.rs
index ed67630bcac44..5af2006f08146 100644
--- a/src/test/run-pass/issue-9396.rs
+++ b/src/test/run-pass/issue-9396.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 use std::sync::mpsc::{TryRecvError, channel};
 use std::thread;
 
diff --git a/src/test/run-pass/ivec-tag.rs b/src/test/run-pass/ivec-tag.rs
index 3f0daf2610ce9..e7498f7c1741d 100644
--- a/src/test/run-pass/ivec-tag.rs
+++ b/src/test/run-pass/ivec-tag.rs
@@ -9,6 +9,7 @@
 // except according to those terms.
 
 // pretty-expanded FIXME #23616
+// ignore-emscripten no threads support
 
 #![feature(std_misc)]
 
diff --git a/src/test/run-pass/logging-only-prints-once.rs b/src/test/run-pass/logging-only-prints-once.rs
index 1b1cdcb1102a2..11ab43fd08763 100644
--- a/src/test/run-pass/logging-only-prints-once.rs
+++ b/src/test/run-pass/logging-only-prints-once.rs
@@ -9,6 +9,7 @@
 // except according to those terms.
 
 // ignore-windows
+// ignore-emscripten no threads support
 // exec-env:RUST_LOG=debug
 
 use std::cell::Cell;
diff --git a/src/test/run-pass/macro-with-braces-in-expr-position.rs b/src/test/run-pass/macro-with-braces-in-expr-position.rs
index 326d1cafe6c78..c3fad3a19f927 100644
--- a/src/test/run-pass/macro-with-braces-in-expr-position.rs
+++ b/src/test/run-pass/macro-with-braces-in-expr-position.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 use std::thread;
 
 macro_rules! expr { ($e: expr) => { $e } }
diff --git a/src/test/run-pass/moves-based-on-type-capture-clause.rs b/src/test/run-pass/moves-based-on-type-capture-clause.rs
index c7ef9776367bd..d3c028070fd14 100644
--- a/src/test/run-pass/moves-based-on-type-capture-clause.rs
+++ b/src/test/run-pass/moves-based-on-type-capture-clause.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 #![feature(std_misc)]
 
 use std::thread;
diff --git a/src/test/run-pass/nested-vec-3.rs b/src/test/run-pass/nested-vec-3.rs
index 89ac626158392..458b6c16e62a7 100644
--- a/src/test/run-pass/nested-vec-3.rs
+++ b/src/test/run-pass/nested-vec-3.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 // Test that using the `vec!` macro nested within itself works when
 // the contents implement Drop and we hit a panic in the middle of
 // construction.
diff --git a/src/test/run-pass/no-landing-pads.rs b/src/test/run-pass/no-landing-pads.rs
index d90e7ef5e473d..8445bccf13493 100644
--- a/src/test/run-pass/no-landing-pads.rs
+++ b/src/test/run-pass/no-landing-pads.rs
@@ -9,7 +9,7 @@
 // except according to those terms.
 
 // compile-flags: -Z no-landing-pads
-
+// ignore-emscripten no threads support
 
 use std::thread;
 
diff --git a/src/test/run-pass/panic-handler-flail-wildly.rs b/src/test/run-pass/panic-handler-flail-wildly.rs
index 783a44beaf36a..39ea987f71ba4 100644
--- a/src/test/run-pass/panic-handler-flail-wildly.rs
+++ b/src/test/run-pass/panic-handler-flail-wildly.rs
@@ -9,6 +9,8 @@
 // except according to those terms.
 #![feature(panic_handler, std_panic)]
 
+// ignore-emscripten no threads support
+
 use std::panic;
 use std::thread;
 
diff --git a/src/test/run-pass/panic-handler-set-twice.rs b/src/test/run-pass/panic-handler-set-twice.rs
index edf65e8e2aa69..ed9a02c1d3ecc 100644
--- a/src/test/run-pass/panic-handler-set-twice.rs
+++ b/src/test/run-pass/panic-handler-set-twice.rs
@@ -9,6 +9,8 @@
 // except according to those terms.
 #![feature(panic_handler, const_fn, std_panic)]
 
+// ignore-emscripten no threads support
+
 use std::sync::atomic::{AtomicUsize, Ordering};
 use std::panic;
 use std::thread;
diff --git a/src/test/run-pass/panic-in-dtor-drops-fields.rs b/src/test/run-pass/panic-in-dtor-drops-fields.rs
index f84a823d3db22..c5f92fbd55aad 100644
--- a/src/test/run-pass/panic-in-dtor-drops-fields.rs
+++ b/src/test/run-pass/panic-in-dtor-drops-fields.rs
@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
 
 use std::thread;
 
diff --git a/src/test/run-pass/panic-recover-propagate.rs b/src/test/run-pass/panic-recover-propagate.rs
index c0b2f25d99c07..d420ef99863c2 100644
--- a/src/test/run-pass/panic-recover-propagate.rs
+++ b/src/test/run-pass/panic-recover-propagate.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 #![feature(std_panic, recover, panic_propagate, panic_handler, const_fn)]
 
 use std::sync::atomic::{AtomicUsize, Ordering};
diff --git a/src/test/run-pass/process-sigpipe.rs b/src/test/run-pass/process-sigpipe.rs
index 5bff4fa080a34..ebc7f13461045 100644
--- a/src/test/run-pass/process-sigpipe.rs
+++ b/src/test/run-pass/process-sigpipe.rs
@@ -18,6 +18,8 @@
 // (instead of running forever), and that it does not print an error
 // message about a broken pipe.
 
+// ignore-emscripten no threads support
+
 use std::process;
 use std::thread;
 
diff --git a/src/test/run-pass/rust-log-filter.rs b/src/test/run-pass/rust-log-filter.rs
index 59179206104f8..306d24e317754 100644
--- a/src/test/run-pass/rust-log-filter.rs
+++ b/src/test/run-pass/rust-log-filter.rs
@@ -9,7 +9,7 @@
 // except according to those terms.
 
 // exec-env:RUST_LOG=rust_log_filter/foo
-
+// ignore-emscripten no threads support
 
 #![allow(unknown_features)]
 #![feature(box_syntax, std_misc, rustc_private)]
diff --git a/src/test/run-pass/send-resource.rs b/src/test/run-pass/send-resource.rs
index 66878d98c840c..7dd1c3c597876 100644
--- a/src/test/run-pass/send-resource.rs
+++ b/src/test/run-pass/send-resource.rs
@@ -9,6 +9,7 @@
 // except according to those terms.
 
 // pretty-expanded FIXME #23616
+// ignore-emscripten no threads support
 
 #![feature(std_misc)]
 
diff --git a/src/test/run-pass/sendfn-spawn-with-fn-arg.rs b/src/test/run-pass/sendfn-spawn-with-fn-arg.rs
index 63ffa552405be..fb5877b8a4898 100644
--- a/src/test/run-pass/sendfn-spawn-with-fn-arg.rs
+++ b/src/test/run-pass/sendfn-spawn-with-fn-arg.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 #![allow(unknown_features)]
 #![feature(box_syntax)]
 
diff --git a/src/test/run-pass/sepcomp-unwind.rs b/src/test/run-pass/sepcomp-unwind.rs
index 766e2b6b7228f..96e9c1ed2ccf9 100644
--- a/src/test/run-pass/sepcomp-unwind.rs
+++ b/src/test/run-pass/sepcomp-unwind.rs
@@ -10,6 +10,7 @@
 
 // ignore-bitrig
 // compile-flags: -C codegen-units=3
+// ignore-emscripten no threads support
 
 // Test unwinding through multiple compilation units.
 
diff --git a/src/test/run-pass/slice-panic-1.rs b/src/test/run-pass/slice-panic-1.rs
index ed949fe082877..afec06adc864f 100644
--- a/src/test/run-pass/slice-panic-1.rs
+++ b/src/test/run-pass/slice-panic-1.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 // Test that if a slicing expr[..] fails, the correct cleanups happen.
 
 
diff --git a/src/test/run-pass/slice-panic-2.rs b/src/test/run-pass/slice-panic-2.rs
index 4103c9495e102..2932b585b8805 100644
--- a/src/test/run-pass/slice-panic-2.rs
+++ b/src/test/run-pass/slice-panic-2.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 // Test that if a slicing expr[..] fails, the correct cleanups happen.
 
 
diff --git a/src/test/run-pass/spawn-fn.rs b/src/test/run-pass/spawn-fn.rs
index 4a35ed609e080..751d833ff9c8b 100644
--- a/src/test/run-pass/spawn-fn.rs
+++ b/src/test/run-pass/spawn-fn.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 use std::thread;
 
 fn x(s: String, n: isize) {
diff --git a/src/test/run-pass/spawn-types.rs b/src/test/run-pass/spawn-types.rs
index ae4fabd34d629..cab190d025f8b 100644
--- a/src/test/run-pass/spawn-types.rs
+++ b/src/test/run-pass/spawn-types.rs
@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
 
 /*
   Make sure we can spawn tasks that take different types of
diff --git a/src/test/run-pass/spawn.rs b/src/test/run-pass/spawn.rs
index 00be41a27d2c2..c9a030cf053c7 100644
--- a/src/test/run-pass/spawn.rs
+++ b/src/test/run-pass/spawn.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 use std::thread;
 
 pub fn main() {
diff --git a/src/test/run-pass/spawn2.rs b/src/test/run-pass/spawn2.rs
index 93dc3faaa205d..2a5fab8a20927 100644
--- a/src/test/run-pass/spawn2.rs
+++ b/src/test/run-pass/spawn2.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 use std::thread;
 
 pub fn main() {
diff --git a/src/test/run-pass/spawning-with-debug.rs b/src/test/run-pass/spawning-with-debug.rs
index 858b7a83c6274..c09ddf5296661 100644
--- a/src/test/run-pass/spawning-with-debug.rs
+++ b/src/test/run-pass/spawning-with-debug.rs
@@ -10,6 +10,7 @@
 
 // ignore-windows
 // exec-env:RUST_LOG=debug
+// ignore-emscripten no threads support
 
 // regression test for issue #10405, make sure we don't call println! too soon.
 
diff --git a/src/test/run-pass/task-comm-0.rs b/src/test/run-pass/task-comm-0.rs
index 1409caf9c702d..0ac232e2e12b3 100644
--- a/src/test/run-pass/task-comm-0.rs
+++ b/src/test/run-pass/task-comm-0.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 #![feature(std_misc)]
 
 use std::thread;
diff --git a/src/test/run-pass/task-comm-1.rs b/src/test/run-pass/task-comm-1.rs
index b3327d82c3ebe..9a43780f08f01 100644
--- a/src/test/run-pass/task-comm-1.rs
+++ b/src/test/run-pass/task-comm-1.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 #![feature(std_misc)]
 
 use std::thread;
diff --git a/src/test/run-pass/task-comm-10.rs b/src/test/run-pass/task-comm-10.rs
index ced240502ed8b..13b40f17292fb 100644
--- a/src/test/run-pass/task-comm-10.rs
+++ b/src/test/run-pass/task-comm-10.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 #![feature(std_misc)]
 
 use std::thread;
diff --git a/src/test/run-pass/task-comm-11.rs b/src/test/run-pass/task-comm-11.rs
index 7af8f5d3b3575..be846795962da 100644
--- a/src/test/run-pass/task-comm-11.rs
+++ b/src/test/run-pass/task-comm-11.rs
@@ -9,6 +9,7 @@
 // except according to those terms.
 
 // pretty-expanded FIXME #23616
+// ignore-emscripten no threads support
 
 #![feature(std_misc)]
 
diff --git a/src/test/run-pass/task-comm-12.rs b/src/test/run-pass/task-comm-12.rs
index a3dfa361cecd6..fdf02e65d8eb3 100644
--- a/src/test/run-pass/task-comm-12.rs
+++ b/src/test/run-pass/task-comm-12.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 #![feature(std_misc)]
 
 use std::thread;
diff --git a/src/test/run-pass/task-comm-13.rs b/src/test/run-pass/task-comm-13.rs
index 156ddd9c77fc3..46c5d3a7ce32b 100644
--- a/src/test/run-pass/task-comm-13.rs
+++ b/src/test/run-pass/task-comm-13.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 #![feature(std_misc)]
 
 use std::sync::mpsc::{channel, Sender};
diff --git a/src/test/run-pass/task-comm-14.rs b/src/test/run-pass/task-comm-14.rs
index 90f68deb303e8..e75a6cf0c8709 100644
--- a/src/test/run-pass/task-comm-14.rs
+++ b/src/test/run-pass/task-comm-14.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 #![feature(std_misc)]
 
 use std::sync::mpsc::{channel, Sender};
diff --git a/src/test/run-pass/task-comm-15.rs b/src/test/run-pass/task-comm-15.rs
index 2994b9c538490..f2ff48ebd95a9 100644
--- a/src/test/run-pass/task-comm-15.rs
+++ b/src/test/run-pass/task-comm-15.rs
@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
 // pretty-expanded FIXME #23616
 
 #![feature(std_misc)]
diff --git a/src/test/run-pass/task-comm-17.rs b/src/test/run-pass/task-comm-17.rs
index 8f6f971ce35c8..fe00f1aba363b 100644
--- a/src/test/run-pass/task-comm-17.rs
+++ b/src/test/run-pass/task-comm-17.rs
@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
 // pretty-expanded FIXME #23616
 
 #![feature(std_misc)]
diff --git a/src/test/run-pass/task-comm-3.rs b/src/test/run-pass/task-comm-3.rs
index 890107998ccb7..0e8542bababdd 100644
--- a/src/test/run-pass/task-comm-3.rs
+++ b/src/test/run-pass/task-comm-3.rs
@@ -10,6 +10,7 @@
 
 #![feature(std_misc)]
 
+// ignore-emscripten no threads support
 // no-pretty-expanded FIXME #15189
 
 use std::thread;
diff --git a/src/test/run-pass/task-comm-7.rs b/src/test/run-pass/task-comm-7.rs
index e37160f979c26..7b2b9fde9ee4a 100644
--- a/src/test/run-pass/task-comm-7.rs
+++ b/src/test/run-pass/task-comm-7.rs
@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
 
 #![feature(std_misc)]
 #![allow(dead_assignment)]
diff --git a/src/test/run-pass/task-comm-9.rs b/src/test/run-pass/task-comm-9.rs
index d8eec4169e353..75fd1826b5853 100644
--- a/src/test/run-pass/task-comm-9.rs
+++ b/src/test/run-pass/task-comm-9.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 #![feature(std_misc)]
 
 use std::thread;
diff --git a/src/test/run-pass/task-life-0.rs b/src/test/run-pass/task-life-0.rs
index ba8819fd0b0fe..312a9f4992501 100644
--- a/src/test/run-pass/task-life-0.rs
+++ b/src/test/run-pass/task-life-0.rs
@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
 // pretty-expanded FIXME #23616
 
 #![feature(std_misc)]
diff --git a/src/test/run-pass/task-spawn-move-and-copy.rs b/src/test/run-pass/task-spawn-move-and-copy.rs
index 6a84ec47c93a1..9b9081019e482 100644
--- a/src/test/run-pass/task-spawn-move-and-copy.rs
+++ b/src/test/run-pass/task-spawn-move-and-copy.rs
@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
 
 #![allow(unknown_features)]
 #![feature(box_syntax, std_misc)]
diff --git a/src/test/run-pass/task-stderr.rs b/src/test/run-pass/task-stderr.rs
index 4a1bb5a5916f0..1f64f40c5255b 100644
--- a/src/test/run-pass/task-stderr.rs
+++ b/src/test/run-pass/task-stderr.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 #![feature(box_syntax, set_stdio)]
 
 use std::io::prelude::*;
diff --git a/src/test/run-pass/tcp-stress.rs b/src/test/run-pass/tcp-stress.rs
index dca65f03f690a..52c920b6f5e03 100644
--- a/src/test/run-pass/tcp-stress.rs
+++ b/src/test/run-pass/tcp-stress.rs
@@ -12,6 +12,7 @@
 // ignore-bitrig system ulimit (Too many open files)
 // ignore-netbsd system ulimit (Too many open files)
 // ignore-openbsd system ulimit (Too many open files)
+// ignore-emscripten no threads or sockets support
 
 use std::io::prelude::*;
 use std::net::{TcpListener, TcpStream};
diff --git a/src/test/run-pass/terminate-in-initializer.rs b/src/test/run-pass/terminate-in-initializer.rs
index 83eb351df530f..2875f73fc6cfa 100644
--- a/src/test/run-pass/terminate-in-initializer.rs
+++ b/src/test/run-pass/terminate-in-initializer.rs
@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
 
 // Issue #787
 // Don't try to clean up uninitialized locals
diff --git a/src/test/run-pass/threads.rs b/src/test/run-pass/threads.rs
index 184338c3294ff..8c5b84b2c82c3 100644
--- a/src/test/run-pass/threads.rs
+++ b/src/test/run-pass/threads.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 #![feature(std_misc)]
 
 use std::thread;
diff --git a/src/test/run-pass/tls-dtors-are-run-in-a-static-binary.rs b/src/test/run-pass/tls-dtors-are-run-in-a-static-binary.rs
index da30100f67ff9..82e586196e379 100644
--- a/src/test/run-pass/tls-dtors-are-run-in-a-static-binary.rs
+++ b/src/test/run-pass/tls-dtors-are-run-in-a-static-binary.rs
@@ -9,6 +9,7 @@
 // except according to those terms.
 
 // no-prefer-dynamic
+// ignore-emscripten no threads support
 
 static mut HIT: bool = false;
 
diff --git a/src/test/run-pass/tls-init-on-init.rs b/src/test/run-pass/tls-init-on-init.rs
index 195b814492af1..b44c535d3a487 100644
--- a/src/test/run-pass/tls-init-on-init.rs
+++ b/src/test/run-pass/tls-init-on-init.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 #![feature(thread_local_state)]
 
 use std::thread::{self, LocalKeyState};
diff --git a/src/test/run-pass/trait-bounds-in-arc.rs b/src/test/run-pass/trait-bounds-in-arc.rs
index 9aa2badd80b94..24dc73d4a43d1 100644
--- a/src/test/run-pass/trait-bounds-in-arc.rs
+++ b/src/test/run-pass/trait-bounds-in-arc.rs
@@ -11,6 +11,7 @@
 // Tests that a heterogeneous list of existential types can be put inside an Arc
 // and shared between threads as long as all types fulfill Send.
 
+// ignore-emscripten no threads support
 // ignore-pretty
 
 #![allow(unknown_features)]
diff --git a/src/test/run-pass/unique-send-2.rs b/src/test/run-pass/unique-send-2.rs
index c32483f629e03..2e864797db056 100644
--- a/src/test/run-pass/unique-send-2.rs
+++ b/src/test/run-pass/unique-send-2.rs
@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
 
 #![allow(unknown_features)]
 #![feature(box_syntax)]
diff --git a/src/test/run-pass/unit-like-struct-drop-run.rs b/src/test/run-pass/unit-like-struct-drop-run.rs
index e31d4c811fc63..eaee3505a67ca 100644
--- a/src/test/run-pass/unit-like-struct-drop-run.rs
+++ b/src/test/run-pass/unit-like-struct-drop-run.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 // Make sure the destructor is run for unit-like structs.
 
 
diff --git a/src/test/run-pass/unwind-resource.rs b/src/test/run-pass/unwind-resource.rs
index 449e500edbe84..85ee21e090255 100644
--- a/src/test/run-pass/unwind-resource.rs
+++ b/src/test/run-pass/unwind-resource.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 use std::sync::mpsc::{channel, Sender};
 use std::thread;
 
diff --git a/src/test/run-pass/unwind-unique.rs b/src/test/run-pass/unwind-unique.rs
index 07bfc8062f9d4..320a11f64d8ac 100644
--- a/src/test/run-pass/unwind-unique.rs
+++ b/src/test/run-pass/unwind-unique.rs
@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
 
 #![allow(unknown_features)]
 #![feature(box_syntax)]
diff --git a/src/test/run-pass/vector-sort-panic-safe.rs b/src/test/run-pass/vector-sort-panic-safe.rs
index 42b05aeea2910..a4202217840e6 100644
--- a/src/test/run-pass/vector-sort-panic-safe.rs
+++ b/src/test/run-pass/vector-sort-panic-safe.rs
@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
 
 #![feature(rand, num_bits_bytes)]
 #![feature(const_fn)]
diff --git a/src/test/run-pass/weak-lang-item.rs b/src/test/run-pass/weak-lang-item.rs
index 5a567758bf45f..d9f4ec2892035 100644
--- a/src/test/run-pass/weak-lang-item.rs
+++ b/src/test/run-pass/weak-lang-item.rs
@@ -10,6 +10,7 @@
 
 // aux-build:weak-lang-items.rs
 
+// ignore-emscripten no threads support
 // pretty-expanded FIXME #23616
 
 extern crate weak_lang_items as other;
diff --git a/src/test/run-pass/yield.rs b/src/test/run-pass/yield.rs
index 45a747509589d..db884638622d1 100644
--- a/src/test/run-pass/yield.rs
+++ b/src/test/run-pass/yield.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 use std::thread;
 
 pub fn main() {
diff --git a/src/test/run-pass/yield1.rs b/src/test/run-pass/yield1.rs
index 69d8431082c2f..cab68794e1cc4 100644
--- a/src/test/run-pass/yield1.rs
+++ b/src/test/run-pass/yield1.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten no threads support
+
 use std::thread;
 
 pub fn main() {