diff --git a/.circleci/config.yml b/.circleci/config.yml
index eedf08d27d..15ca09e010 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -44,6 +44,13 @@ commands:
           command: |
             wget https://dl.google.com/linux/direct/google-chrome-stable_current_amd64.deb
             sudo apt install ./google-chrome-stable_current_amd64.deb
+  install-wasmtime:
+    steps:
+      - run:
+          name: "Install wasmtime"
+          command: |
+            curl https://wasmtime.dev/install.sh -sSf | bash
+            sudo ln -s ~/.wasmtime/bin/wasmtime /usr/local/bin/wasmtime
   install-xtensa-toolchain:
     parameters:
       variant:
@@ -91,6 +98,7 @@ commands:
           llvm: "<<parameters.llvm>>"
       - install-node
       - install-chrome
+      - install-wasmtime
       - restore_cache:
           keys:
             - go-cache-v2-{{ checksum "go.mod" }}-{{ .Environment.CIRCLE_PREVIOUS_BUILD_NUM }}
@@ -134,6 +142,7 @@ commands:
                 gcc-avr \
                 avr-libc
       - install-node
+      - install-wasmtime
       - install-xtensa-toolchain:
           variant: "linux-amd64"
       - restore_cache:
@@ -194,6 +203,7 @@ commands:
                 gcc-avr \
                 avr-libc
       - install-node
+      - install-wasmtime
       - install-xtensa-toolchain:
           variant: "linux-amd64"
       - restore_cache:
diff --git a/loader/goroot.go b/loader/goroot.go
index 9648550719..5fa4bea071 100644
--- a/loader/goroot.go
+++ b/loader/goroot.go
@@ -189,7 +189,7 @@ func mergeDirectory(goroot, tinygoroot, tmpgoroot, importPath string, overrides
 // with the TinyGo version. This is the case on some targets.
 func needsSyscallPackage(buildTags []string) bool {
 	for _, tag := range buildTags {
-		if tag == "baremetal" || tag == "darwin" || tag == "nintendoswitch" {
+		if tag == "baremetal" || tag == "darwin" || tag == "nintendoswitch" || tag == "wasi" {
 			return true
 		}
 	}
diff --git a/main_test.go b/main_test.go
index f66117b90a..ac01baafaa 100644
--- a/main_test.go
+++ b/main_test.go
@@ -98,6 +98,10 @@ func TestCompiler(t *testing.T) {
 				runPlatTests("wasm", matches, t)
 			})
 		}
+
+		t.Run("WASI", func(t *testing.T) {
+			runPlatTests("wasi", matches, t)
+		})
 	}
 }
 
@@ -109,7 +113,6 @@ func runPlatTests(target string, matches []string, t *testing.T) {
 
 		t.Run(filepath.Base(path), func(t *testing.T) {
 			t.Parallel()
-
 			runTest(path, target, t)
 		})
 	}
@@ -161,6 +164,11 @@ func runTest(path, target string, t *testing.T) {
 		PrintSizes: "",
 		WasmAbi:    "js",
 	}
+
+	if target == "wasi" {
+		config.WasmAbi = "generic"
+	}
+
 	binary := filepath.Join(tmpdir, "test")
 	err = runBuild("./"+path, binary, config)
 	if err != nil {
diff --git a/src/os/file_unix.go b/src/os/file_unix.go
index e77d6773fb..84d738b0ca 100644
--- a/src/os/file_unix.go
+++ b/src/os/file_unix.go
@@ -1,4 +1,4 @@
-// +build darwin linux,!baremetal freebsd,!baremetal
+// +build darwin linux,!baremetal,!wasi freebsd,!baremetal
 
 package os
 
diff --git a/src/runtime/arch_arm.go b/src/runtime/arch_arm.go
index 0a98f6d532..e2dc4b5bfe 100644
--- a/src/runtime/arch_arm.go
+++ b/src/runtime/arch_arm.go
@@ -1,4 +1,4 @@
-// +build arm,!baremetal arm,arm7tdmi
+// +build arm,!baremetal,!wasm arm,arm7tdmi
 
 package runtime
 
diff --git a/src/runtime/runtime_unix.go b/src/runtime/runtime_unix.go
index a3c2b4471b..ef4b825856 100644
--- a/src/runtime/runtime_unix.go
+++ b/src/runtime/runtime_unix.go
@@ -1,4 +1,4 @@
-// +build darwin linux,!baremetal freebsd,!baremetal
+// +build darwin linux,!baremetal,!wasi freebsd,!baremetal
 // +build !nintendoswitch
 
 package runtime
diff --git a/src/runtime/runtime_unix_heap.go b/src/runtime/runtime_unix_heap.go
index 14168f4387..1aefd2f615 100644
--- a/src/runtime/runtime_unix_heap.go
+++ b/src/runtime/runtime_unix_heap.go
@@ -1,4 +1,4 @@
-// +build darwin linux,!baremetal freebsd,!baremetal
+// +build darwin linux,!baremetal,!wasi freebsd,!baremetal
 // +build !nintendoswitch
 
 // +build gc.conservative gc.leaking
diff --git a/src/runtime/runtime_unix_noheap.go b/src/runtime/runtime_unix_noheap.go
index bf7f675987..f9826ac5d7 100644
--- a/src/runtime/runtime_unix_noheap.go
+++ b/src/runtime/runtime_unix_noheap.go
@@ -1,4 +1,4 @@
-// +build darwin linux,!baremetal freebsd,!baremetal
+// +build darwin linux,!baremetal,!wasi freebsd,!baremetal
 
 // +build !nintendoswitch
 
diff --git a/src/runtime/runtime_wasm.go b/src/runtime/runtime_wasm.go
index aaf95d7846..e37d432e04 100644
--- a/src/runtime/runtime_wasm.go
+++ b/src/runtime/runtime_wasm.go
@@ -2,35 +2,26 @@
 
 package runtime
 
-import "unsafe"
-
-type timeUnit float64 // time in milliseconds, just like Date.now() in JavaScript
+import (
+	"unsafe"
+)
 
-// Implements __wasi_ciovec_t and __wasi_iovec_t.
-type wasiIOVec struct {
+// Implements __wasi_iovec_t.
+type __wasi_iovec_t struct {
 	buf    unsafe.Pointer
 	bufLen uint
 }
 
 //go:wasm-module wasi_unstable
 //export fd_write
-func fd_write(id uint32, iovs *wasiIOVec, iovs_len uint, nwritten *uint) (errno uint)
+func fd_write(id uint32, iovs *__wasi_iovec_t, iovs_len uint, nwritten *uint) (errno uint)
 
 func postinit() {}
 
-//export _start
-func _start() {
-	// These need to be initialized early so that the heap can be initialized.
-	heapStart = uintptr(unsafe.Pointer(&heapStartSymbol))
-	heapEnd = uintptr(wasm_memory_size(0) * wasmPageSize)
-
-	run()
-}
-
 // Using global variables to avoid heap allocation.
 var (
 	putcharBuf   = byte(0)
-	putcharIOVec = wasiIOVec{
+	putcharIOVec = __wasi_iovec_t{
 		buf:    unsafe.Pointer(&putcharBuf),
 		bufLen: 1,
 	}
@@ -44,49 +35,6 @@ func putchar(c byte) {
 	fd_write(stdout, &putcharIOVec, 1, &nwritten)
 }
 
-var handleEvent func()
-
-//go:linkname setEventHandler syscall/js.setEventHandler
-func setEventHandler(fn func()) {
-	handleEvent = fn
-}
-
-//export resume
-func resume() {
-	go func() {
-		handleEvent()
-	}()
-	scheduler()
-}
-
-//export go_scheduler
-func go_scheduler() {
-	scheduler()
-}
-
-const asyncScheduler = true
-
-func ticksToNanoseconds(ticks timeUnit) int64 {
-	// The JavaScript API works in float64 milliseconds, so convert to
-	// nanoseconds first before converting to a timeUnit (which is a float64),
-	// to avoid precision loss.
-	return int64(ticks * 1e6)
-}
-
-func nanosecondsToTicks(ns int64) timeUnit {
-	// The JavaScript API works in float64 milliseconds, so convert to timeUnit
-	// (which is a float64) first before dividing, to avoid precision loss.
-	return timeUnit(ns) / 1e6
-}
-
-// This function is called by the scheduler.
-// Schedule a call to runtime.scheduler, do not actually sleep.
-//export runtime.sleepTicks
-func sleepTicks(d timeUnit)
-
-//export runtime.ticks
-func ticks() timeUnit
-
 // Abort executes the wasm 'unreachable' instruction.
 func abort() {
 	trap()
diff --git a/src/runtime/runtime_wasm_js.go b/src/runtime/runtime_wasm_js.go
new file mode 100644
index 0000000000..ea1cc6e41d
--- /dev/null
+++ b/src/runtime/runtime_wasm_js.go
@@ -0,0 +1,59 @@
+// +build wasm,!wasi
+
+package runtime
+
+import "unsafe"
+
+type timeUnit float64 // time in milliseconds, just like Date.now() in JavaScript
+
+//export _start
+func _start() {
+	// These need to be initialized early so that the heap can be initialized.
+	heapStart = uintptr(unsafe.Pointer(&heapStartSymbol))
+	heapEnd = uintptr(wasm_memory_size(0) * wasmPageSize)
+
+	run()
+}
+
+var handleEvent func()
+
+//go:linkname setEventHandler syscall/js.setEventHandler
+func setEventHandler(fn func()) {
+	handleEvent = fn
+}
+
+//export resume
+func resume() {
+	go func() {
+		handleEvent()
+	}()
+	scheduler()
+}
+
+//export go_scheduler
+func go_scheduler() {
+	scheduler()
+}
+
+const asyncScheduler = true
+
+func ticksToNanoseconds(ticks timeUnit) int64 {
+	// The JavaScript API works in float64 milliseconds, so convert to
+	// nanoseconds first before converting to a timeUnit (which is a float64),
+	// to avoid precision loss.
+	return int64(ticks * 1e6)
+}
+
+func nanosecondsToTicks(ns int64) timeUnit {
+	// The JavaScript API works in float64 milliseconds, so convert to timeUnit
+	// (which is a float64) first before dividing, to avoid precision loss.
+	return timeUnit(ns) / 1e6
+}
+
+// This function is called by the scheduler.
+// Schedule a call to runtime.scheduler, do not actually sleep.
+//export runtime.sleepTicks
+func sleepTicks(d timeUnit)
+
+//export runtime.ticks
+func ticks() timeUnit
diff --git a/src/runtime/runtime_wasm_wasi.go b/src/runtime/runtime_wasm_wasi.go
new file mode 100644
index 0000000000..99a34ebb4f
--- /dev/null
+++ b/src/runtime/runtime_wasm_wasi.go
@@ -0,0 +1,117 @@
+// +build wasm,wasi
+
+package runtime
+
+import (
+	"unsafe"
+)
+
+type timeUnit int64
+
+//export _start
+func _start() {
+	// These need to be initialized early so that the heap can be initialized.
+	heapStart = uintptr(unsafe.Pointer(&heapStartSymbol))
+	heapEnd = uintptr(wasm_memory_size(0) * wasmPageSize)
+	run()
+}
+
+func ticksToNanoseconds(ticks timeUnit) int64 {
+	return int64(ticks)
+}
+
+func nanosecondsToTicks(ns int64) timeUnit {
+	return timeUnit(ns)
+}
+
+const (
+	asyncScheduler           = false
+	timePrecisionNanoseconds = 1000 // TODO: how can we determine the appropriate `precision`?
+)
+
+var (
+	sleepTicksSubscription = __wasi_subscription_t{
+		userData: 0,
+		u: __wasi_subscription_u_t{
+			tag: __wasi_eventtype_t_clock,
+			u: __wasi_subscription_clock_t{
+				userData:  0,
+				id:        0,
+				timeout:   0,
+				precision: timePrecisionNanoseconds,
+				flags:     0,
+			},
+		},
+	}
+	sleepTicksResult  = __wasi_event_t{}
+	sleepTicksNEvents uint32
+)
+
+func sleepTicks(d timeUnit) {
+	sleepTicksSubscription.u.u.timeout = int64(d)
+	poll_oneoff(&sleepTicksSubscription, &sleepTicksResult, 1, &sleepTicksNEvents)
+}
+
+func ticks() timeUnit {
+	var nano int64
+	clock_time_get(0, timePrecisionNanoseconds, &nano)
+	return timeUnit(nano)
+}
+
+// Implementations of wasi_unstable APIs
+
+//go:wasm-module wasi_unstable
+//export clock_time_get
+func clock_time_get(clockid uint32, precision uint64, time *int64) (errno uint16)
+
+//go:wasm-module wasi_unstable
+//export poll_oneoff
+func poll_oneoff(in *__wasi_subscription_t, out *__wasi_event_t, nsubscriptions uint32, nevents *uint32) (errno uint16)
+
+type __wasi_eventtype_t = uint8
+
+const (
+	__wasi_eventtype_t_clock __wasi_eventtype_t = 0
+	// TODO: __wasi_eventtype_t_fd_read  __wasi_eventtype_t = 1
+	// TODO: __wasi_eventtype_t_fd_write __wasi_eventtype_t = 2
+)
+
+type (
+	// https://github.com/wasmerio/wasmer/blob/1.0.0-alpha3/lib/wasi/src/syscalls/types.rs#L584-L588
+	__wasi_subscription_t struct {
+		userData uint64
+		u        __wasi_subscription_u_t
+	}
+
+	__wasi_subscription_u_t struct {
+		tag __wasi_eventtype_t
+
+		// TODO: support fd_read/fd_write event
+		u __wasi_subscription_clock_t
+	}
+
+	// https://github.com/wasmerio/wasmer/blob/1.0.0-alpha3/lib/wasi/src/syscalls/types.rs#L711-L718
+	__wasi_subscription_clock_t struct {
+		userData  uint64
+		id        uint32
+		timeout   int64
+		precision int64
+		flags     uint16
+	}
+)
+
+type (
+	// https://github.com/wasmerio/wasmer/blob/1.0.0-alpha3/lib/wasi/src/syscalls/types.rs#L191-L198
+	__wasi_event_t struct {
+		userData  uint64
+		errno     uint16
+		eventType __wasi_eventtype_t
+
+		// only used for fd_read or fd_write events
+		// TODO: support fd_read/fd_write event
+		_ struct {
+			nBytes uint64
+			flags  uint16
+		}
+	}
+)
diff --git a/src/syscall/syscall_baremetal.go b/src/syscall/syscall_baremetal.go
index 28fa39ba85..2331101ba3 100644
--- a/src/syscall/syscall_baremetal.go
+++ b/src/syscall/syscall_baremetal.go
@@ -1,4 +1,4 @@
-// +build baremetal
+// +build baremetal wasi
 
 package syscall
 
diff --git a/src/syscall/tables_baremetal.go b/src/syscall/tables_baremetal.go
index 47a536bffd..9677d77a09 100644
--- a/src/syscall/tables_baremetal.go
+++ b/src/syscall/tables_baremetal.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build baremetal nintendoswitch
+// +build baremetal nintendoswitch wasi
 
 package syscall
 
diff --git a/targets/wasi.json b/targets/wasi.json
new file mode 100644
index 0000000000..97f7848f9b
--- /dev/null
+++ b/targets/wasi.json
@@ -0,0 +1,22 @@
+{
+	"llvm-target":   "wasm32--wasi",
+	"build-tags":    ["wasm", "wasi"],
+	"goos":          "linux",
+	"goarch":        "arm",
+	"compiler":      "clang",
+	"linker":        "wasm-ld",
+	"cflags": [
+		"--target=wasm32--wasi",
+		"--sysroot={root}/lib/wasi-libc/sysroot",
+		"-Oz"
+	],
+	"ldflags": [
+		"--allow-undefined",
+		"--no-threads",
+		"--stack-first",
+		"--export-dynamic",
+		"--no-demangle",
+		"{root}/lib/wasi-libc/sysroot/lib/wasm32-wasi/libc.a"
+	],
+	"emulator":      ["wasmtime"]
+}
diff --git a/transform/gc.go b/transform/gc.go
index 9329644522..0688604986 100644
--- a/transform/gc.go
+++ b/transform/gc.go
@@ -19,6 +19,7 @@ func MakeGCStackSlots(mod llvm.Module) bool {
 		}
 		stackChainStart := mod.NamedGlobal("runtime.stackChainStart")
 		if !stackChainStart.IsNil() {
+			stackChainStart.SetLinkage(llvm.InternalLinkage)
 			stackChainStart.SetInitializer(llvm.ConstNull(stackChainStart.Type().ElementType()))
 			stackChainStart.SetGlobalConstant(true)
 		}
@@ -94,6 +95,7 @@ func MakeGCStackSlots(mod llvm.Module) bool {
 		}
 		return false
 	}
+	stackChainStart.SetLinkage(llvm.InternalLinkage)
 	stackChainStartType := stackChainStart.Type().ElementType()
 	stackChainStart.SetInitializer(llvm.ConstNull(stackChainStartType))
 
@@ -333,11 +335,13 @@ func AddGlobalsBitmap(mod llvm.Module) bool {
 	// Update trackedGlobalsStart, which points to the globals bundle.
 	trackedGlobalsStart := llvm.ConstPtrToInt(globalsBundle, uintptrType)
 	mod.NamedGlobal("runtime.trackedGlobalsStart").SetInitializer(trackedGlobalsStart)
+	mod.NamedGlobal("runtime.trackedGlobalsStart").SetLinkage(llvm.InternalLinkage)
 
 	// Update trackedGlobalsLength, which contains the length (in words) of the
 	// globals bundle.
 	alignment := targetData.PrefTypeAlignment(llvm.PointerType(ctx.Int8Type(), 0))
 	trackedGlobalsLength := llvm.ConstInt(uintptrType, targetData.TypeAllocSize(globalsBundleType)/uint64(alignment), false)
+	mod.NamedGlobal("runtime.trackedGlobalsLength").SetLinkage(llvm.InternalLinkage)
 	mod.NamedGlobal("runtime.trackedGlobalsLength").SetInitializer(trackedGlobalsLength)
 
 	// Create a bitmap (a new global) that stores for each word in the globals
@@ -357,6 +361,7 @@ func AddGlobalsBitmap(mod llvm.Module) bool {
 	bitmapOld.ReplaceAllUsesWith(llvm.ConstBitCast(bitmapNew, bitmapOld.Type()))
 	bitmapNew.SetInitializer(bitmapArray)
 	bitmapNew.SetName("runtime.trackedGlobalsBitmap")
+	bitmapNew.SetLinkage(llvm.InternalLinkage)
 
 	return true // the IR was changed
 }
diff --git a/transform/testdata/gc-globals.out.ll b/transform/testdata/gc-globals.out.ll
index 45b80b7d84..905e8eafa1 100644
--- a/transform/testdata/gc-globals.out.ll
+++ b/transform/testdata/gc-globals.out.ll
@@ -7,11 +7,11 @@ target triple = "wasm32-unknown-unknown-wasm"
 @globalInt = global i32 5
 @constString = constant %runtime._string zeroinitializer
 @constInterface = constant %runtime._interface zeroinitializer
-@runtime.trackedGlobalsLength = global i32 4
+@runtime.trackedGlobalsLength = internal global i32 4
 @runtime.trackedGlobalsBitmap = external global [0 x i8]
-@runtime.trackedGlobalsStart = global i32 ptrtoint ({ %runtime._string, %runtime._interface }* @tinygo.trackedGlobals to i32)
+@runtime.trackedGlobalsStart = internal global i32 ptrtoint ({ %runtime._string, %runtime._interface }* @tinygo.trackedGlobals to i32)
 @tinygo.trackedGlobals = internal unnamed_addr global { %runtime._string, %runtime._interface } zeroinitializer
-@runtime.trackedGlobalsBitmap.1 = global [1 x i8] c"\09"
+@runtime.trackedGlobalsBitmap.1 = internal global [1 x i8] c"\09"
 
 define void @main() {
   %1 = load i32, i32* @globalInt
diff --git a/transform/testdata/gc-stackslots.out.ll b/transform/testdata/gc-stackslots.out.ll
index efcc3ed25e..9acb0abe7d 100644
--- a/transform/testdata/gc-stackslots.out.ll
+++ b/transform/testdata/gc-stackslots.out.ll
@@ -3,7 +3,7 @@ target triple = "wasm32-unknown-unknown-wasm"
 
 %runtime.stackChainObject = type { %runtime.stackChainObject*, i32 }
 
-@runtime.stackChainStart = global %runtime.stackChainObject* null
+@runtime.stackChainStart = internal global %runtime.stackChainObject* null
 @someGlobal = global i8 3
 
 declare void @runtime.trackPointer(i8* nocapture readonly)