llgo/ssa: unreachable

cl/_testcgo/unreachable/in.go

@@ -0,0 +1,14 @@
+package main
+
+import (
+	"github.com/goplus/llgo/internal/runtime/c"
+)
+
+func foo() {
+	c.Unreachable()
+}
+
+func main() {
+	foo()
+	c.Printf(c.String("Hello\n"))
+}

cl/_testcgo/unreachable/out.ll

@@ -0,0 +1,38 @@
+; ModuleID = 'main'
+source_filename = "main"
+
+%"github.com/goplus/llgo/internal/runtime.String" = type { ptr, i64 }
+
+@"main.init$guard" = global ptr null
+
+define void @main.foo() {
+_llgo_0:
+  unreachable
+  ret void
+}
+
+define void @main.init() {
+_llgo_0:
+  %0 = load i1, ptr @"main.init$guard", align 1
+  br i1 %0, label %_llgo_2, label %_llgo_1
+
+_llgo_1:                                          ; preds = %_llgo_0
+  store i1 true, ptr @"main.init$guard", align 1
+  br label %_llgo_2
+
+_llgo_2:                                          ; preds = %_llgo_1, %_llgo_0
+  ret void
+}
+
+define void @main() {
+_llgo_0:
+  call void @main.init()
+  call void @main.foo()
+  %0 = call ptr @"github.com/goplus/llgo/internal/runtime/c.String"([7 x i8] c"Hello\0A\00")
+  %1 = call i32 (ptr, ...) @printf(ptr %0)
+  ret void
+}
+
+declare ptr @"github.com/goplus/llgo/internal/runtime/c.String"(%"github.com/goplus/llgo/internal/runtime.String")
+
+declare i32 @printf(ptr, ...)

cl/compile.go

@@ -329,6 +329,8 @@ func (p *context) compileInstrOrValue(b llssa.Builder, iv instrOrValue, asValue
 				ret = cstr(b, call.Args)
 			case llgoAlloca:
 				ret = p.alloca(b, call.Args)
+			case llgoUnreachable:
+				b.Unreachable()
 			default:
 				panic("todo")
 			}

ssa/stmt_builder.go

@@ -76,6 +76,11 @@ func (b Builder) Panic(v Expr) {
 	b.impl.CreateUnreachable() // TODO(xsw): pass v
 }
 
+// Unreachable emits an unreachable instruction.
+func (b Builder) Unreachable() {
+	b.impl.CreateUnreachable()
+}
+
 // Return emits a return instruction.
 func (b Builder) Return(results ...Expr) {
 	if debugInstr {