cmd/compile, runtime: remove throwreturn

Change-Id: If8d27cf1cd8d650ed0ba332448d3174d80b6b0ca
Reviewed-on: https://go-review.googlesource.com/29217
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/cmd/compile/internal/gc/builtin/runtime.go

@@ -16,7 +16,6 @@ func newobject(typ *byte) *any
 func panicindex()
 func panicslice()
 func panicdivide()
-func throwreturn()
 func throwinit()
 func panicwrap(string, string, string)
 

src/cmd/compile/internal/gc/go.go

@@ -404,8 +404,6 @@ var panicslice *Node
 
 var panicdivide *Node
 
-var throwreturn *Node
-
 var growslice *Node
 
 var writebarrierptr *Node

src/cmd/compile/internal/gc/pgen.go

@@ -310,7 +310,6 @@ func compile(fn *Node) {
 		Panicindex = Sysfunc("panicindex")
 		panicslice = Sysfunc("panicslice")
 		panicdivide = Sysfunc("panicdivide")
-		throwreturn = Sysfunc("throwreturn")
 		growslice = Sysfunc("growslice")
 		writebarrierptr = Sysfunc("writebarrierptr")
 		typedmemmove = Sysfunc("typedmemmove")

src/runtime/panic.go

@@ -62,10 +62,6 @@ func panicmem() {
 	panic(memoryError)
 }
 
-func throwreturn() {
-	throw("no return at end of a typed function - compiler is broken")
-}
-
 func throwinit() {
 	throw("recursive call during initialization - linker skew")
 }