[dev.typeparams] cmd/compile: desugar ORECOVER into ORECOVERFP

Currently ORECOVER is a single operation that both (1) calculates
the (logical) caller frame pointer and (2) calls runtime.gorecover.
This is normally fine, but it's inconvenient for regabi, which wants
to wrap "defer recover()" into "defer func() { recover() }" and
needs (1) and (2) to happen at different times.

The current solution is to apply walkRecover early to split it into
the two steps, but calling it during order is a minor layering
violation. It works well today because the order and walk phases are
closely related anyway and walkRecover is relatively simple, but it
won't work for go/defer wrapping earlier into the frontend.

This CL adds a new, lower-level ORECOVERFP primitive, which represents
just part (2); and OGETCALLER{PC,SP} primitives, which provide a way
to compute (1) in the frontend too.

OGETCALLERPC isn't needed/used today, but it seems worth including for
completeness. Maybe it will be useful at some point for intrinsifying
runtime.getcaller{pc,sp}, like we already do for runtime.getg.

Change-Id: Iaa8ae51e09306c45c147b6759a5b7c24dcc317ca
Reviewed-on: https://go-review.googlesource.com/c/go/+/330192
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/src/cmd/compile/internal/typecheck/typecheck.go b/src/cmd/compile/internal/typecheck/typecheck.go
index 0367f7b034..f7de43c79f 100644
--- a/src/cmd/compile/internal/typecheck/typecheck.go
+++ b/src/cmd/compile/internal/typecheck/typecheck.go
@@ -776,6 +776,10 @@ func typecheck1(n ir.Node, top int) ir.Node {
 		n := n.(*ir.CallExpr)
 		return tcRecover(n)
 
+	case ir.ORECOVERFP:
+		n := n.(*ir.CallExpr)
+		return tcRecoverFP(n)
+
 	case ir.OUNSAFEADD:
 		n := n.(*ir.BinaryExpr)
 		return tcUnsafeAdd(n)
@@ -809,6 +813,14 @@ func typecheck1(n ir.Node, top int) ir.Node {
 		n.SetType(types.Types[types.TUINTPTR])
 		return n
 
+	case ir.OGETCALLERPC, ir.OGETCALLERSP:
+		n := n.(*ir.CallExpr)
+		if len(n.Args) != 0 {
+			base.FatalfAt(n.Pos(), "unexpected arguments: %v", n)
+		}
+		n.SetType(types.Types[types.TUINTPTR])
+		return n
+
 	case ir.OCONVNOP:
 		n := n.(*ir.ConvExpr)
 		n.X = Expr(n.X)