targets/gba: implement interrupt handler

compiler/compiler.go

@@ -1309,7 +1309,7 @@ func (c *Compiler) parseCall(frame *Frame, instr *ssa.CallCommon) (llvm.Value, e
 			return c.emitVolatileLoad(frame, instr)
 		case strings.HasPrefix(name, "runtime/volatile.Store"):
 			return c.emitVolatileStore(frame, instr)
-		case name == "runtime/interrupt.New":
+		case name == "runtime/interrupt.New" && len(fn.Blocks) == 0:
 			return c.emitInterruptGlobal(frame, instr)
 		}
 

src/runtime/interrupt/interrupt.go

@@ -12,19 +12,3 @@ type Interrupt struct {
 	// some encapsulation.
 	num int
 }
-
-// New is a compiler intrinsic that creates a new Interrupt object. You may call
-// it only once, and must pass constant parameters to it. That means that the
-// interrupt ID must be a Go constant and that the handler must be a simple
-// function: closures are not supported.
-func New(id int, handler func(Interrupt)) Interrupt
-
-// Register is used to declare an interrupt. You should not normally call this
-// function: it is only for telling the compiler about the mapping between an
-// interrupt number and the interrupt handler name.
-func Register(id int, handlerName string) int
-
-type handle struct {
-	handler func(Interrupt)
-	Interrupt
-}

src/runtime/interrupt/interrupt_gameboyadvance.go

@@ -0,0 +1,59 @@
+// +build gameboyadvance
+
+package interrupt
+
+import (
+	"runtime/volatile"
+	"unsafe"
+)
+
+var handlers = [14]func(Interrupt){}
+
+const (
+	IRQ_VBLANK  = 0
+	IRQ_HBLANK  = 1
+	IRQ_VCOUNT  = 2
+	IRQ_TIMER0  = 3
+	IRQ_TIMER1  = 4
+	IRQ_TIMER2  = 5
+	IRQ_TIMER3  = 6
+	IRQ_COM     = 7
+	IRQ_DMA0    = 8
+	IRQ_DMA1    = 9
+	IRQ_DMA2    = 10
+	IRQ_DMA3    = 11
+	IRQ_KEYPAD  = 12
+	IRQ_GAMEPAK = 13
+)
+
+var (
+	regInterruptEnable = (*volatile.Register16)(unsafe.Pointer(uintptr(0x4000200)))
+	regInterruptRequestFlags = (*volatile.Register16)(unsafe.Pointer(uintptr(0x4000202)))
+	regInterruptMasterEnable = (*volatile.Register16)(unsafe.Pointer(uintptr(0x4000208)))
+)
+
+// New creates a new Interrupt object. Do not call it multiple times. If you do,
+// make sure the interrupt is disabled while you do so. The last call will set
+// the active interrupt handler.
+func New(id int, handler func(Interrupt)) Interrupt {
+	handlers[id] = handler
+	return Interrupt{id}
+}
+
+// Enable enables this interrupt. Right after calling this function, the
+// interrupt may be invoked if it was already pending.
+func (irq Interrupt) Enable() {
+	regInterruptEnable.SetBits(1 << irq.num)
+}
+
+//export handleInterrupt
+func handleInterrupt() {
+	flags := regInterruptRequestFlags.Get()
+	for i := range handlers {
+		if flags & (1 << i) != 0 {
+			irq := Interrupt{i}
+			regInterruptRequestFlags.Set(1 << i) // acknowledge interrupt
+			handlers[i](irq)
+		}
+	}
+}

src/runtime/interrupt/interrupt_vectored.go

@@ -0,0 +1,19 @@
+// +build avr riscv,baremetal cortexm
+
+package interrupt
+
+// New is a compiler intrinsic that creates a new Interrupt object. You may call
+// it only once, and must pass constant parameters to it. That means that the
+// interrupt ID must be a Go constant and that the handler must be a simple
+// function: closures are not supported.
+func New(id int, handler func(Interrupt)) Interrupt
+
+// Register is used to declare an interrupt. You should not normally call this
+// function: it is only for telling the compiler about the mapping between an
+// interrupt number and the interrupt handler name.
+func Register(id int, handlerName string) int
+
+type handle struct {
+	handler func(Interrupt)
+	Interrupt
+}

src/runtime/runtime_arm7tdmi.go

@@ -4,6 +4,7 @@ package runtime
 
 import (
 	"unsafe"
+	_ "runtime/interrupt" // make sure the interrupt handler is defined
 )
 
 type timeUnit int64

targets/gameboy-advance.ld

@@ -1,10 +1,13 @@
 OUTPUT_ARCH(arm)
 ENTRY(_start)
 
+/* Note: iwram is reduced by 96 bytes because the last part of that RAM
+ * (starting at 0x03007FA0) is used for interrupt handling.
+ */
 MEMORY {
-    ewram   : ORIGIN = 0x02000000, LENGTH = 256K /* on-board work RAM (2 wait states) */
-    iwram   : ORIGIN = 0x03000000, LENGTH = 32K  /* in-chip work RAM (faster) */
-    rom     : ORIGIN = 0x08000000, LENGTH = 32M  /* flash ROM */
+    ewram   : ORIGIN = 0x02000000, LENGTH = 256K   /* on-board work RAM (2 wait states) */
+    iwram   : ORIGIN = 0x03000000, LENGTH = 32K-96 /* in-chip work RAM (faster) */
+    rom     : ORIGIN = 0x08000000, LENGTH = 32M    /* flash ROM */
 }
 
 __stack_size_irq = 1K;

targets/gameboy-advance.s

@@ -17,9 +17,7 @@ _start:
     .byte   0x00,0x00              // Checksum (80000BEh)
 
 start_vector:
-    mov     r0, #0x4000000                 // REG_BASE
-    str     r0, [r0, #0x208]
-
+    // Configure stacks
     mov     r0, #0x12                      // Switch to IRQ Mode
     msr     cpsr, r0
     ldr     sp, =__sp_irq                  // Set IRQ stack
@@ -27,7 +25,21 @@ start_vector:
     msr     cpsr, r0
     ldr     sp, =__sp_usr                  // Set user stack
 
+    // Configure interrupt handler
+    mov     r0, #0x4000000                 // REG_BASE
+    ldr     r1, =handleInterruptARM
+    str     r1, [r0, #-4]                  // actually storing to 0x03007FFC due to mirroring
+
+    // Enable interrupts
+    mov     r1, #1
+    str     r1, [r0, #0x208]               // 0x04000208 Interrupt Master Enable
+
     // Jump to user code (switching to Thumb mode)
     ldr     r3, =main
     bx      r3
 
+// Small interrupt handler that immediately jumps to a function defined in the
+// program (in Thumb) for further processing.
+handleInterruptARM:
+    ldr     r0, =handleInterrupt
+    bx      r0