diff --git a/stdlib/private/StdlibUnittest/StdlibUnittest.swift b/stdlib/private/StdlibUnittest/StdlibUnittest.swift
index 51ac487875af9..019de920c4201 100644
--- a/stdlib/private/StdlibUnittest/StdlibUnittest.swift
+++ b/stdlib/private/StdlibUnittest/StdlibUnittest.swift
@@ -1449,7 +1449,12 @@ public func runAllTests() {
   if _isChildProcess {
     _childProcess()
   } else {
+    #if os(WASI)
+    // WASI doesn't support child process
+    var runTestsInProcess: Bool = true
+    #else
     var runTestsInProcess: Bool = false
+    #endif
     var filter: String?
     var args = [String]()
     var i = 0
diff --git a/stdlib/public/WASI/CMakeLists.txt b/stdlib/public/WASI/CMakeLists.txt
index 451f1f3af57d7..0d088443ad7be 100644
--- a/stdlib/public/WASI/CMakeLists.txt
+++ b/stdlib/public/WASI/CMakeLists.txt
@@ -1,3 +1,4 @@
 add_swift_target_library(swiftWasiPthread STATIC IS_STDLIB
   Pthread.cpp
+  TARGET_SDKS WASI
   INSTALL_IN_COMPONENT stdlib)
diff --git a/stdlib/public/stubs/CommandLine.cpp b/stdlib/public/stubs/CommandLine.cpp
index 0b4506391beeb..cf371e5ababe4 100644
--- a/stdlib/public/stubs/CommandLine.cpp
+++ b/stdlib/public/stubs/CommandLine.cpp
@@ -206,6 +206,42 @@ char ** _swift_stdlib_getUnsafeArgvArgc(int *outArgLen) {
     
   return outBuf;
 }
+#elif defined(__wasi__)
+#include <wasi/api.h>
+#include <wasi/libc.h>
+#include <stdlib.h>
+
+SWIFT_RUNTIME_STDLIB_API
+char ** _swift_stdlib_getUnsafeArgvArgc(int *outArgLen) {
+  assert(outArgLen != nullptr);
+
+  if (_swift_stdlib_ProcessOverrideUnsafeArgv) {
+    *outArgLen = _swift_stdlib_ProcessOverrideUnsafeArgc;
+    return _swift_stdlib_ProcessOverrideUnsafeArgv;
+  }
+
+  __wasi_errno_t err;
+
+  size_t argv_buf_size;
+  size_t argc;
+  err = __wasi_args_sizes_get(&argc, &argv_buf_size);
+  if (err != __WASI_ERRNO_SUCCESS) return nullptr;
+
+  size_t num_ptrs = argc + 1;
+  char *argv_buf = (char *)malloc(argv_buf_size);
+  char **argv = (char **)calloc(num_ptrs, sizeof(char *));
+
+  err = __wasi_args_get((uint8_t **)argv, (uint8_t *)argv_buf);
+  if (err != __WASI_ERRNO_SUCCESS) {
+    free(argv_buf);
+    free(argv);
+    return nullptr;
+  }
+
+  *outArgLen = static_cast<int>(argc);
+
+  return argv;
+}
 #else // Add your favorite OS's command line arg grabber here.
 SWIFT_RUNTIME_STDLIB_API
 char ** _swift_stdlib_getUnsafeArgvArgc(int *outArgLen) {
diff --git a/test/stdlib/mmap.swift b/test/stdlib/mmap.swift
index 6879941e9f7dd..7008923d4c660 100644
--- a/test/stdlib/mmap.swift
+++ b/test/stdlib/mmap.swift
@@ -1,6 +1,7 @@
 // RUN: %target-run-simple-swift %t
 // REQUIRES: executable_test
 // UNSUPPORTED: OS=windows-msvc
+// UNSUPPORTED: OS=wasi
 
 import StdlibUnittest
 #if os(macOS) || os(iOS) || os(tvOS) || os(watchOS)
diff --git a/test/stdlib/simd_diagnostics.swift b/test/stdlib/simd_diagnostics.swift
index 2aa1be085bc37..d2230cc2a0970 100644
--- a/test/stdlib/simd_diagnostics.swift
+++ b/test/stdlib/simd_diagnostics.swift
@@ -1,7 +1,7 @@
 // RUN: %target-typecheck-verify-swift
 
 // FIXME: No simd module on linux rdar://problem/20795411
-// XFAIL: linux, windows
+// XFAIL: linux, windows, wasm
 
 import simd