[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>

12 files changed, 94 insertions, 32 deletions

diff --git a/src/cmd/compile/internal/escape/call.go b/src/cmd/compile/internal/escape/call.go
index 8511259d47..1f2d59af35 100644
--- a/src/cmd/compile/internal/escape/call.go
+++ b/src/cmd/compile/internal/escape/call.go
@@ -123,11 +123,14 @@ func (e *escape) callCommon(ks []hole, call ir.Node, where *ir.GoDeferStmt) {
 		call := call.(*ir.BinaryExpr)
 		argument(e.discardHole(), &call.X)
 		argument(e.discardHole(), &call.Y)
+
 	case ir.ODELETE, ir.OPRINT, ir.OPRINTN, ir.ORECOVER:
 		call := call.(*ir.CallExpr)
+		fixRecoverCall(call)
 		for i := range call.Args {
 			argument(e.discardHole(), &call.Args[i])
 		}
+
 	case ir.OLEN, ir.OCAP, ir.OREAL, ir.OIMAG, ir.OCLOSE:
 		call := call.(*ir.UnaryExpr)
 		argument(e.discardHole(), &call.X)
diff --git a/src/cmd/compile/internal/escape/desugar.go b/src/cmd/compile/internal/escape/desugar.go
new file mode 100644
index 0000000000..8b3cc25cf9
--- /dev/null
+++ b/src/cmd/compile/internal/escape/desugar.go
@@ -0,0 +1,37 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package escape
+
+import (
+	"cmd/compile/internal/base"
+	"cmd/compile/internal/ir"
+	"cmd/compile/internal/typecheck"
+	"cmd/compile/internal/types"
+)
+
+// TODO(mdempsky): Desugaring doesn't belong during escape analysis,
+// but for now it's the most convenient place for some rewrites.
+
+// fixRecoverCall rewrites an ORECOVER call into ORECOVERFP,
+// adding an explicit frame pointer argument.
+// If call is not an ORECOVER call, it's left unmodified.
+func fixRecoverCall(call *ir.CallExpr) {
+	if call.Op() != ir.ORECOVER {
+		return
+	}
+
+	pos := call.Pos()
+
+	// FP is equal to caller's SP plus FixedFrameSize().
+	var fp ir.Node = ir.NewCallExpr(pos, ir.OGETCALLERSP, nil, nil)
+	if off := base.Ctxt.FixedFrameSize(); off != 0 {
+		fp = ir.NewBinaryExpr(fp.Pos(), ir.OADD, fp, ir.NewInt(off))
+	}
+	// TODO(mdempsky): Replace *int32 with unsafe.Pointer, without upsetting checkptr.
+	fp = ir.NewConvExpr(pos, ir.OCONVNOP, types.NewPtr(types.Types[types.TINT32]), fp)
+
+	call.SetOp(ir.ORECOVERFP)
+	call.Args = []ir.Node{typecheck.Expr(fp)}
+}
diff --git a/src/cmd/compile/internal/escape/expr.go b/src/cmd/compile/internal/escape/expr.go
index cb95221dd5..c10e866990 100644
--- a/src/cmd/compile/internal/escape/expr.go
+++ b/src/cmd/compile/internal/escape/expr.go
@@ -43,7 +43,7 @@ func (e *escape) exprSkipInit(k hole, n ir.Node) {
 	default:
 		base.Fatalf("unexpected expr: %s %v", n.Op().String(), n)
 
-	case ir.OLITERAL, ir.ONIL, ir.OGETG, ir.OTYPE, ir.OMETHEXPR, ir.OLINKSYMOFFSET:
+	case ir.OLITERAL, ir.ONIL, ir.OGETG, ir.OGETCALLERPC, ir.OGETCALLERSP, ir.OTYPE, ir.OMETHEXPR, ir.OLINKSYMOFFSET:
 		// nop
 
 	case ir.ONAME:
@@ -138,7 +138,7 @@ func (e *escape) exprSkipInit(k hole, n ir.Node) {
 		n := n.(*ir.UnaryExpr)
 		e.discard(n.X)
 
-	case ir.OCALLMETH, ir.OCALLFUNC, ir.OCALLINTER, ir.OLEN, ir.OCAP, ir.OCOMPLEX, ir.OREAL, ir.OIMAG, ir.OAPPEND, ir.OCOPY, ir.OUNSAFEADD, ir.OUNSAFESLICE:
+	case ir.OCALLMETH, ir.OCALLFUNC, ir.OCALLINTER, ir.OLEN, ir.OCAP, ir.OCOMPLEX, ir.OREAL, ir.OIMAG, ir.OAPPEND, ir.OCOPY, ir.ORECOVER, ir.OUNSAFEADD, ir.OUNSAFESLICE:
 		e.call([]hole{k}, n)
 
 	case ir.ONEW:
@@ -158,9 +158,6 @@ func (e *escape) exprSkipInit(k hole, n ir.Node) {
 		e.spill(k, n)
 		e.discard(n.Len)
 
-	case ir.ORECOVER:
-		// nop
-
 	case ir.OCALLPART:
 		// Flow the receiver argument to both the closure and
 		// to the receiver parameter.
diff --git a/src/cmd/compile/internal/ir/expr.go b/src/cmd/compile/internal/ir/expr.go
index b46fd905fe..4659b99fbf 100644
--- a/src/cmd/compile/internal/ir/expr.go
+++ b/src/cmd/compile/internal/ir/expr.go
@@ -180,8 +180,12 @@ func (n *CallExpr) SetOp(op Op) {
 	switch op {
 	default:
 		panic(n.no("SetOp " + op.String()))
-	case OCALL, OCALLFUNC, OCALLINTER, OCALLMETH,
-		OAPPEND, ODELETE, OGETG, OMAKE, OPRINT, OPRINTN, ORECOVER:
+	case OAPPEND,
+		OCALL, OCALLFUNC, OCALLINTER, OCALLMETH,
+		ODELETE,
+		OGETG, OGETCALLERPC, OGETCALLERSP,
+		OMAKE, OPRINT, OPRINTN,
+		ORECOVER, ORECOVERFP:
 		n.op = op
 	}
 }
diff --git a/src/cmd/compile/internal/ssagen/ssa.go b/src/cmd/compile/internal/ssagen/ssa.go
index 659ba02b5b..93847a39a3 100644
--- a/src/cmd/compile/internal/ssagen/ssa.go
+++ b/src/cmd/compile/internal/ssagen/ssa.go
@@ -3135,6 +3135,14 @@ func (s *state) expr(n ir.Node) *ssa.Value {
 		n := n.(*ir.CallExpr)
 		return s.newValue1(ssa.OpGetG, n.Type(), s.mem())
 
+	case ir.OGETCALLERPC:
+		n := n.(*ir.CallExpr)
+		return s.newValue0(ssa.OpGetCallerPC, n.Type())
+
+	case ir.OGETCALLERSP:
+		n := n.(*ir.CallExpr)
+		return s.newValue0(ssa.OpGetCallerSP, n.Type())
+
 	case ir.OAPPEND:
 		return s.append(n.(*ir.CallExpr), false)
 
diff --git a/src/cmd/compile/internal/typecheck/func.go b/src/cmd/compile/internal/typecheck/func.go
index bd21977f26..031279f42c 100644
--- a/src/cmd/compile/internal/typecheck/func.go
+++ b/src/cmd/compile/internal/typecheck/func.go
@@ -967,6 +967,21 @@ func tcRecover(n *ir.CallExpr) ir.Node {
 	return n
 }
 
+// tcRecoverFP typechecks an ORECOVERFP node.
+func tcRecoverFP(n *ir.CallExpr) ir.Node {
+	if len(n.Args) != 1 {
+		base.FatalfAt(n.Pos(), "wrong number of arguments: %v", n)
+	}
+
+	n.Args[0] = Expr(n.Args[0])
+	if !n.Args[0].Type().IsPtrShaped() {
+		base.FatalfAt(n.Pos(), "%L is not pointer shaped", n.Args[0])
+	}
+
+	n.SetType(types.Types[types.TINTER])
+	return n
+}
+
 // tcUnsafeAdd typechecks an OUNSAFEADD node.
 func tcUnsafeAdd(n *ir.BinaryExpr) *ir.BinaryExpr {
 	if !types.AllowsGoVersion(curpkg(), 1, 17) {
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)
diff --git a/src/cmd/compile/internal/walk/builtin.go b/src/cmd/compile/internal/walk/builtin.go
index be0f4c5208..135eaee6bc 100644
--- a/src/cmd/compile/internal/walk/builtin.go
+++ b/src/cmd/compile/internal/walk/builtin.go
@@ -641,16 +641,9 @@ func walkPrint(nn *ir.CallExpr, init *ir.Nodes) ir.Node {
 	return walkStmt(typecheck.Stmt(r))
 }
 
-// walkRecover walks an ORECOVER node.
-func walkRecover(nn *ir.CallExpr, init *ir.Nodes) ir.Node {
-	// Call gorecover with the FP of this frame.
-	// FP is equal to caller's SP plus FixedFrameSize().
-	var fp ir.Node = mkcall("getcallersp", types.Types[types.TUINTPTR], init)
-	if off := base.Ctxt.FixedFrameSize(); off != 0 {
-		fp = ir.NewBinaryExpr(fp.Pos(), ir.OADD, fp, ir.NewInt(off))
-	}
-	fp = ir.NewConvExpr(fp.Pos(), ir.OCONVNOP, types.NewPtr(types.Types[types.TINT32]), fp)
-	return mkcall("gorecover", nn.Type(), init, fp)
+// walkRecover walks an ORECOVERFP node.
+func walkRecoverFP(nn *ir.CallExpr, init *ir.Nodes) ir.Node {
+	return mkcall("gorecover", nn.Type(), init, walkExpr(nn.Args[0], init))
 }
 
 func walkUnsafeSlice(n *ir.BinaryExpr, init *ir.Nodes) ir.Node {
diff --git a/src/cmd/compile/internal/walk/expr.go b/src/cmd/compile/internal/walk/expr.go
index 2fb907710b..070954be27 100644
--- a/src/cmd/compile/internal/walk/expr.go
+++ b/src/cmd/compile/internal/walk/expr.go
@@ -82,7 +82,7 @@ func walkExpr1(n ir.Node, init *ir.Nodes) ir.Node {
 		base.Fatalf("walkExpr: switch 1 unknown op %+v", n.Op())
 		panic("unreachable")
 
-	case ir.ONONAME, ir.OGETG:
+	case ir.OGETG, ir.OGETCALLERPC, ir.OGETCALLERSP:
 		return n
 
 	case ir.OTYPE, ir.ONAME, ir.OLITERAL, ir.ONIL, ir.OLINKSYMOFFSET:
@@ -161,8 +161,8 @@ func walkExpr1(n ir.Node, init *ir.Nodes) ir.Node {
 		n := n.(*ir.UnaryExpr)
 		return mkcall("gopanic", nil, init, n.X)
 
-	case ir.ORECOVER:
-		return walkRecover(n.(*ir.CallExpr), init)
+	case ir.ORECOVERFP:
+		return walkRecoverFP(n.(*ir.CallExpr), init)
 
 	case ir.OCFUNC:
 		return n
diff --git a/src/cmd/compile/internal/walk/order.go b/src/cmd/compile/internal/walk/order.go
index 75657cd3e4..ff8e95b330 100644
--- a/src/cmd/compile/internal/walk/order.go
+++ b/src/cmd/compile/internal/walk/order.go
@@ -777,10 +777,10 @@ func (o *orderState) stmt(n ir.Node) {
 		o.out = append(o.out, n)
 		o.cleanTemp(t)
 
-	case ir.OPRINT, ir.OPRINTN, ir.ORECOVER:
+	case ir.OPRINT, ir.OPRINTN, ir.ORECOVERFP:
 		n := n.(*ir.CallExpr)
 		t := o.markTemp()
-		o.exprList(n.Args)
+		o.call(n)
 		o.out = append(o.out, n)
 		o.cleanTemp(t)
 
@@ -790,13 +790,6 @@ func (o *orderState) stmt(n ir.Node) {
 		t := o.markTemp()
 		o.init(n.Call)
 		o.call(n.Call)
-		if n.Call.Op() == ir.ORECOVER {
-			// Special handling of "defer recover()". We need to evaluate the FP
-			// argument before wrapping.
-			var init ir.Nodes
-			n.Call = walkRecover(n.Call.(*ir.CallExpr), &init)
-			o.stmtList(init)
-		}
 		o.wrapGoDefer(n)
 		o.out = append(o.out, n)
 		o.cleanTemp(t)
@@ -1270,7 +1263,7 @@ func (o *orderState) expr1(n, lhs ir.Node) ir.Node {
 		ir.OMAKESLICECOPY,
 		ir.ONEW,
 		ir.OREAL,
-		ir.ORECOVER,
+		ir.ORECOVERFP,
 		ir.OSTR2BYTES,
 		ir.OSTR2BYTESTMP,
 		ir.OSTR2RUNES:
diff --git a/src/cmd/compile/internal/walk/stmt.go b/src/cmd/compile/internal/walk/stmt.go
index 2352719da3..bcc0a3e517 100644
--- a/src/cmd/compile/internal/walk/stmt.go
+++ b/src/cmd/compile/internal/walk/stmt.go
@@ -49,7 +49,7 @@ func walkStmt(n ir.Node) ir.Node {
 		ir.OPRINT,
 		ir.OPRINTN,
 		ir.OPANIC,
-		ir.ORECOVER,
+		ir.ORECOVERFP,
 		ir.OGETG:
 		if n.Typecheck() == 0 {
 			base.Fatalf("missing typecheck: %+v", n)
diff --git a/src/cmd/compile/internal/walk/walk.go b/src/cmd/compile/internal/walk/walk.go
index 26da6e3145..6e992a91b8 100644
--- a/src/cmd/compile/internal/walk/walk.go
+++ b/src/cmd/compile/internal/walk/walk.go
@@ -343,7 +343,7 @@ func mayCall(n ir.Node) bool {
 			ir.OCAP, ir.OIMAG, ir.OLEN, ir.OREAL,
 			ir.OCONVNOP, ir.ODOT,
 			ir.OCFUNC, ir.OIDATA, ir.OITAB, ir.OSPTR,
-			ir.OBYTES2STRTMP, ir.OGETG, ir.OSLICEHEADER:
+			ir.OBYTES2STRTMP, ir.OGETG, ir.OGETCALLERPC, ir.OGETCALLERSP, ir.OSLICEHEADER:
 			// ok: operations that don't require function calls.
 			// Expand as needed.
 		}