all: add WebAssembly backend

src/runtime/arch_arm.go

@@ -2,6 +2,10 @@
 
 package runtime
 
+import (
+	"unsafe"
+)
+
 const GOARCH = "arm"
 
 // The length type used inside strings and slices.
@@ -9,3 +13,6 @@ type lenType uint32
 
 // The bitness of the CPU (e.g. 8, 32, 64).
 const TargetBits = 32
+
+//go:extern _heap_start
+var heapStart unsafe.Pointer

src/runtime/arch_avr.go

@@ -2,6 +2,10 @@
 
 package runtime
 
+import (
+	"unsafe"
+)
+
 const GOARCH = "avr"
 
 // The length type used inside strings and slices.
@@ -9,3 +13,6 @@ type lenType uint16
 
 // The bitness of the CPU (e.g. 8, 32, 64).
 const TargetBits = 8
+
+//go:extern _heap_start
+var heapStart unsafe.Pointer

src/runtime/arch_wasm.go

@@ -2,6 +2,10 @@
 
 package runtime
 
+import (
+	"unsafe"
+)
+
 const GOARCH = "wasm"
 
 // The length type used inside strings and slices.
@@ -9,3 +13,6 @@ type lenType uint32
 
 // The bitness of the CPU (e.g. 8, 32, 64).
 const TargetBits = 32
+
+//go:extern __heap_base
+var heapStart unsafe.Pointer

src/runtime/gc.go

@@ -6,9 +6,6 @@ import (
 	"unsafe"
 )
 
-//go:extern _heap_start
-var heapStart unsafe.Pointer
-
 var heapptr = uintptr(unsafe.Pointer(&heapStart))
 
 func alloc(size uintptr) unsafe.Pointer {

src/runtime/runtime_wasm.go

@@ -0,0 +1,54 @@
+// +build wasm,!arm,!avr
+
+package runtime
+
+type timeUnit int64
+
+const tickMicros = 1
+
+var timestamp timeUnit
+
+// CommonWA: io_get_stdout
+func _Cfunc_io_get_stdout() int32
+
+// CommonWA: resource_write
+func _Cfunc_resource_write(id int32, ptr *uint8, len int32) int32
+
+var stdout int32
+
+func init() {
+	stdout = _Cfunc_io_get_stdout()
+}
+
+//go:export _start
+func _start() {
+	initAll()
+}
+
+//go:export cwa_main
+func cwa_main() {
+	initAll() // _start is not called by olin/cwa so has to be called here
+	mainWrapper()
+}
+
+func putchar(c byte) {
+	_Cfunc_resource_write(stdout, &c, 1)
+}
+
+func sleepTicks(d timeUnit) {
+	// TODO: actually sleep here for the given time.
+	timestamp += d
+}
+
+func ticks() timeUnit {
+	return timestamp
+}
+
+// Align on word boundary.
+func align(ptr uintptr) uintptr {
+	return (ptr + 3) &^ 3
+}
+
+func abort() {
+	// TODO
+}