cmd/compile: fix defer/deferreturn
Make sure we do any just-before-return cleanup on all paths out of a
function, including when recovering. Each exit path should include
deferreturn (if there are any defers) and then the exit
code (e.g. copying heap-escaping return values back to the stack).
Introduce a Defer SSA block type which has two outgoing edges - one the
fallthrough edge (the defer was queued successfully) and one which
immediately returns (the defer had a successful recover() call and
normal execution should resume at the return point).
Fixes #14725
Change-Id: Iad035c9fd25ef8b7a74dafbd7461cf04833d981f
Reviewed-on: https://go-review.googlesource.com/20486
Reviewed-by: David Chase <drchase@google.com>
diff --git a/src/cmd/compile/internal/ssa/gen/genericOps.go b/src/cmd/compile/internal/ssa/gen/genericOps.go
index 3b55ebf..6a49cb7 100644
--- a/src/cmd/compile/internal/ssa/gen/genericOps.go
+++ b/src/cmd/compile/internal/ssa/gen/genericOps.go
@@ -401,6 +401,7 @@
{name: "Plain"}, // a single successor
{name: "If"}, // 2 successors, if control goto Succs[0] else goto Succs[1]
{name: "Call"}, // 1 successor, control is call op (of memory type)
+ {name: "Defer"}, // 2 successors, Succs[0]=defer queued, Succs[1]=defer recovered. control is call op (of memory type)
{name: "Check"}, // 1 successor, control is nilcheck op (of void type)
{name: "Ret"}, // no successors, control value is memory result
{name: "RetJmp"}, // no successors, jumps to b.Aux.(*gc.Sym)
