avr: fix time.Sleep() in init code

In the early days of TinyGo, the idea of `postinit` was to enable
interrupts only after initializers have run. Which kind of makes
sense... except that `time.Sleep` is allowed in init code and
`time.Sleep` requires interrupts to be enabled. Therefore, interrupts
must be enabled while initializers are being run.

This commit simply moves the enabling of interrupts to a point right
before running package initializers. It also removes `runtime.postinit`,
which is not necessary anymore (and was only used on AVR).

Author: aykevl

main_test.go

@@ -171,9 +171,6 @@ func TestCompiler(t *testing.T) {
 			case "float.go", "math.go", "print.go":
 				// Stuck in runtime.printfloat64.
 
-			case "goroutines.go":
-				// The main() never runs.
-
 			case "interface.go":
 				// Several comparison tests fail.
 

src/runtime/runtime_arm7tdmi.go

@@ -28,8 +28,6 @@ var _sidata [0]byte
 //go:extern _edata
 var _edata [0]byte
 
-func postinit() {}
-
 // Entry point for Go. Initialize all packages and call main.main().
 //export main
 func main() {

src/runtime/runtime_atsamd21.go

@@ -13,8 +13,6 @@ import (
 
 type timeUnit int64
 
-func postinit() {}
-
 //export Reset_Handler
 func main() {
 	preinit()

src/runtime/runtime_atsamd51.go

@@ -12,8 +12,6 @@ import (
 
 type timeUnit int64
 
-func postinit() {}
-
 //export Reset_Handler
 func main() {
 	arm.SCB.CPACR.Set(0) // disable FPU if it is enabled

src/runtime/runtime_avr.go

@@ -42,6 +42,7 @@ var _ebss [0]byte
 //export main
 func main() {
 	preinit()
+	initHardware()
 	run()
 	exit(0)
 }
@@ -55,15 +56,13 @@ func preinit() {
 	}
 }
 
-func postinit() {
-	// Enable interrupts after initialization.
-	avr.Asm("sei")
-}
-
-func init() {
+func initHardware() {
 	initUART()
 	machine.InitMonotonicTimer()
 	nextTimerRecalibrate = ticks() + timerRecalibrateInterval
+
+	// Enable interrupts after initialization.
+	avr.Asm("sei")
 }
 
 func ticksToNanoseconds(ticks timeUnit) int64 {

src/runtime/runtime_cortexm_qemu.go

@@ -15,8 +15,6 @@ type timeUnit int64
 
 var timestamp timeUnit
 
-func postinit() {}
-
 //export Reset_Handler
 func main() {
 	preinit()

src/runtime/runtime_esp32xx.go

@@ -14,8 +14,6 @@ func putchar(c byte) {
 	machine.Serial.WriteByte(c)
 }
 
-func postinit() {}
-
 // Initialize .bss: zero-initialized global variables.
 // The .data section has already been loaded by the ROM bootloader.
 func clearbss() {

src/runtime/runtime_esp8266.go

@@ -23,8 +23,6 @@ func putchar(c byte) {
 //export rom_i2c_writeReg
 func rom_i2c_writeReg(block, host_id, reg_add, data uint8)
 
-func postinit() {}
-
 //export main
 func main() {
 	// Clear .bss section. .data has already been loaded by the ROM bootloader.

src/runtime/runtime_fe310.go

@@ -16,8 +16,6 @@ import (
 
 type timeUnit int64
 
-func postinit() {}
-
 //export main
 func main() {
 	// Zero the PLIC enable bits on startup: they are not zeroed at reset.

src/runtime/runtime_k210.go

@@ -15,8 +15,6 @@ import (
 
 type timeUnit int64
 
-func postinit() {}
-
 //export main
 func main() {