cmd/compile: cleanup nodpc and nodfp

Instead of creating a new &nodfp expression for every recover() call,
or a new nodpc variable for every function instrumented by the race
detector, this CL introduces two new uintptr-typed pseudo-variables
callerSP and callerPC. These pseudo-variables act just like calls to
the runtime's getcallersp() and getcallerpc() functions.

For consistency, change runtime.gorecover's builtin stub's parameter
type from "*int32" to "uintptr".

Passes toolstash-check, but toolstash-check -race fails because of
register allocator changes.

Change-Id: I985d644653de2dac8b7b03a28829ad04dfd4f358
Reviewed-on: https://go-review.googlesource.com/99416
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

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

@@ -22,7 +22,7 @@ func throwinit()
 func panicwrap()
 
 func gopanic(interface{})
-func gorecover(*int32) interface{}
+func gorecover(uintptr) interface{}
 func goschedguarded()
 
 func printbool(bool)

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

@@ -2025,10 +2025,6 @@ func addrescapes(n *Node) {
 		// Nothing to do.
 
 	case ONAME:
-		if n == nodfp {
-			break
-		}
-
 		// if this is a tmpname (PAUTO), it was tagged by tmpname as not escaping.
 		// on PPARAM it means something different.
 		if n.Class() == PAUTO && n.Esc == EscNever {

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

@@ -232,8 +232,6 @@ var writearchive bool
 
 var Nacl bool
 
-var nodfp *Node
-
 var disable_checknil int
 
 var autogeneratedPos src.XPos

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

@@ -131,12 +131,7 @@ func (s *ssafn) AllocFrame(f *ssa.Func) {
 		for _, v := range b.Values {
 			if n, ok := v.Aux.(*Node); ok {
 				switch n.Class() {
-				case PPARAM, PPARAMOUT:
-					// Don't modify nodfp; it is a global.
-					if n != nodfp {
-						n.Name.SetUsed(true)
-					}
-				case PAUTO:
+				case PAUTO, PPARAM, PPARAMOUT:
 					n.Name.SetUsed(true)
 				}
 			}

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

@@ -64,21 +64,11 @@ func instrument(fn *Node) {
 	}
 
 	if flag_race {
-		// nodpc is the PC of the caller as extracted by
-		// getcallerpc. We use -widthptr(FP) for x86.
-		// BUG: this will not work on arm.
-		nodpc := *nodfp
-		nodpc.Type = types.Types[TUINTPTR]
-		nodpc.Xoffset = int64(-Widthptr)
-		savedLineno := lineno
+		lno := lineno
 		lineno = src.NoXPos
-		nd := mkcall("racefuncenter", nil, nil, &nodpc)
-
-		fn.Func.Enter.Prepend(nd)
-		nd = mkcall("racefuncexit", nil, nil)
-		fn.Func.Exit.Append(nd)
-		fn.Func.Dcl = append(fn.Func.Dcl, &nodpc)
-		lineno = savedLineno
+		fn.Func.Enter.Prepend(mkcall("racefuncenter", nil, nil, callerPC))
+		fn.Func.Exit.Append(mkcall("racefuncexit", nil, nil))
+		lineno = lno
 	}
 
 	if Debug['W'] != 0 {

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

@@ -1471,6 +1471,12 @@ func (s *state) expr(n *Node) *ssa.Value {
 			sym := funcsym(n.Sym).Linksym()
 			return s.entryNewValue1A(ssa.OpAddr, types.NewPtr(n.Type), sym, s.sb)
 		}
+		switch n {
+		case callerSP:
+			return s.newValue0(ssa.OpGetCallerSP, n.Type)
+		case callerPC:
+			return s.newValue0(ssa.OpGetCallerPC, n.Type)
+		}
 		if s.canSSA(n) {
 			return s.variable(n, n.Type)
 		}
@@ -3468,10 +3474,6 @@ func (s *state) addr(n *Node, bounded bool) *ssa.Value {
 			if v != nil {
 				return v
 			}
-			if n == nodfp {
-				// Special arg that points to the frame pointer (Used by ORECOVER).
-				return s.entryNewValue1A(ssa.OpAddr, t, n, s.sp)
-			}
 			s.Fatalf("addr of undeclared ONAME %v. declared: %v", n, s.decladdrs)
 			return nil
 		case PAUTO:

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

@@ -466,8 +466,19 @@ func finishUniverse() {
 		s1.Block = s.Block
 	}
 
-	nodfp = newname(lookup(".fp"))
-	nodfp.Type = types.Types[TINT32]
-	nodfp.SetClass(PPARAM)
-	nodfp.Name.SetUsed(true)
+	callerSP = newname(lookup(".sp"))
+	callerSP.Type = types.Types[TUINTPTR]
+	callerSP.SetClass(PPARAM)
+	callerSP.Name.SetUsed(true)
+
+	callerPC = newname(lookup(".pc"))
+	callerPC.Type = types.Types[TUINTPTR]
+	callerPC.SetClass(PPARAM)
+	callerPC.Name.SetUsed(true)
 }
+
+var (
+	// Pseudo variables that represent the caller's SP and PC, respectively.
+	callerSP *Node
+	callerPC *Node
+)

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

@@ -604,7 +604,7 @@ opswitch:
 		n = mkcall("gopanic", nil, init, n.Left)
 
 	case ORECOVER:
-		n = mkcall("gorecover", n.Type, init, nod(OADDR, nodfp, nil))
+		n = mkcall("gorecover", n.Type, init, callerSP)
 
 	case OCLOSUREVAR, OCFUNC:
 		n.SetAddable(true)