diff --git a/src/device/arm/arm.go b/src/device/arm/arm.go
index 5374a5d3..ff6f4c53 100644
--- a/src/device/arm/arm.go
+++ b/src/device/arm/arm.go
@@ -32,6 +32,9 @@ package arm
 type __reg uint32
 type RegValue = __reg
 
+type __asm string
+func Asm(s __asm)
+
 const (
 	SCS_BASE  = 0xE000E000
 	NVIC_BASE = SCS_BASE + 0x0100
diff --git a/src/runtime/runtime_nrf.go b/src/runtime/runtime_nrf.go
index da740adf..0b62b498 100644
--- a/src/runtime/runtime_nrf.go
+++ b/src/runtime/runtime_nrf.go
@@ -74,8 +74,8 @@ func monotime() uint64 {
 }
 
 func abort() {
-	// TODO: wfi
 	for {
+		arm.Asm("wfi")
 	}
 }
 
diff --git a/tgo.go b/tgo.go
index c2f38cc2..71d2e00f 100644
--- a/tgo.go
+++ b/tgo.go
@@ -1038,6 +1038,15 @@ func (c *Compiler) parseCall(frame *Frame, instr *ssa.CallCommon, parentHandle l
 	case *ssa.Builtin:
 		return c.parseBuiltin(frame, instr.Args, call.Name())
 	case *ssa.Function:
+		if call.Name() == "Asm" && len(instr.Args) == 1 {
+			// Magic function: insert inline assembly instead of calling it.
+			if named, ok := instr.Args[0].Type().(*types.Named); ok && named.Obj().Name() == "__asm" {
+				fnType := llvm.FunctionType(llvm.VoidType(), []llvm.Type{}, false)
+				asm := constant.StringVal(instr.Args[0].(*ssa.Const).Value)
+				target := llvm.InlineAsm(fnType, asm, "", true, false, 0)
+				return c.builder.CreateCall(target, nil, ""), nil
+			}
+		}
 		targetBlocks := false
 		name := getFunctionName(call, targetBlocks)
 		llvmFn := c.mod.NamedFunction(name)