cmd/compile: better integrate parameter tagging with escape.go

This CL moves parameter tagging to before escape analysis is complete,
so we still have access to EscLocation. This will be useful once
EscLocation starts tracking higher-fidelity escape details.

Notably, this CL stops using n.Esc to record parameter escape analysis
details. Now escape analysis only ever sets n.Esc to EscNone or
EscHeap. (It still defaults to EscUnknown, and is set to EscNever in
some places though.)

Passes toolstash-check.

Updates #33981.

Change-Id: I50a91ea1e38c442092de6cd14e20b211f8f818c9
Reviewed-on: https://go-review.googlesource.com/c/go/+/193178
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

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

@@ -405,19 +405,7 @@ const unsafeUintptrTag = "unsafe-uintptr"
 // marked go:uintptrescapes.
 const uintptrEscapesTag = "uintptr-escapes"
 
-func esctag(fn *Node) {
-	fn.Esc = EscFuncTagged
-
-	narg := 0
-	for _, fs := range types.RecvsParams {
-		for _, f := range fs(fn.Type).Fields().Slice() {
-			narg++
-			f.Note = escparamtag(fn, narg, f)
-		}
-	}
-}
-
-func escparamtag(fn *Node, narg int, f *types.Field) string {
+func (e *Escape) paramTag(fn *Node, narg int, f *types.Field) string {
 	name := func() string {
 		if f.Sym != nil {
 			return f.Sym.Name
@@ -446,8 +434,15 @@ func escparamtag(fn *Node, narg int, f *types.Field) string {
 		// External functions are assumed unsafe, unless
 		// //go:noescape is given before the declaration.
 		if fn.Noescape() {
+			if Debug['m'] != 0 && f.Sym != nil {
+				Warnl(fn.Pos, "%S %v does not escape", funcSym(fn), name())
+			}
 			return mktag(EscNone)
 		}
+
+		if Debug['m'] != 0 && f.Sym != nil {
+			Warnl(fn.Pos, "leaking param: %v", name())
+		}
 		return mktag(EscHeap)
 	}
 
@@ -477,5 +472,26 @@ func escparamtag(fn *Node, narg int, f *types.Field) string {
 	}
 
 	n := asNode(f.Nname)
-	return mktag(int(n.Esc))
+	loc := e.oldLoc(n)
+	esc := finalizeEsc(loc.paramEsc)
+
+	if Debug['m'] != 0 && !loc.escapes {
+		if esc == EscNone {
+			Warnl(n.Pos, "%S %S does not escape", funcSym(fn), n)
+		} else if esc == EscHeap {
+			Warnl(n.Pos, "leaking param: %S", n)
+		} else {
+			if esc&EscContentEscapes != 0 {
+				Warnl(n.Pos, "leaking param content: %S", n)
+			}
+			for i := 0; i < numEscReturns; i++ {
+				if x := getEscReturn(esc, i); x >= 0 {
+					res := n.Name.Curfn.Type.Results().Field(i).Sym
+					Warnl(n.Pos, "leaking param: %S to result %v level=%d", n, res, x)
+				}
+			}
+		}
+	}
+
+	return mktag(int(esc))
 }

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

@@ -147,12 +147,7 @@ func escapeFuncs(fns []*Node, recursive bool) {
 	e.curfn = nil
 
 	e.walkAll()
-	e.finish()
-
-	// Record parameter tags for package export data.
-	for _, fn := range fns {
-		esctag(fn)
-	}
+	e.finish(fns)
 }
 
 func (e *Escape) initFunc(fn *Node) {
@@ -1258,7 +1253,20 @@ func (l *EscLocation) leakTo(sink *EscLocation, derefs int) {
 	}
 }
 
-func (e *Escape) finish() {
+func (e *Escape) finish(fns []*Node) {
+	// Record parameter tags for package export data.
+	for _, fn := range fns {
+		fn.Esc = EscFuncTagged
+
+		narg := 0
+		for _, fs := range types.RecvsParams {
+			for _, f := range fs(fn.Type).Fields().Slice() {
+				narg++
+				f.Note = e.paramTag(fn, narg, f)
+			}
+		}
+	}
+
 	for _, loc := range e.allLocs {
 		n := loc.n
 		if n == nil {
@@ -1279,27 +1287,10 @@ func (e *Escape) finish() {
 			}
 			n.Esc = EscHeap
 			addrescapes(n)
-		} else if loc.isName(PPARAM) {
-			n.Esc = finalizeEsc(loc.paramEsc)
-
-			if Debug['m'] != 0 && types.Haspointers(n.Type) {
-				if n.Esc == EscNone {
-					Warnl(n.Pos, "%S %S does not escape", funcSym(loc.curfn), n)
-				} else if n.Esc == EscHeap {
-					Warnl(n.Pos, "leaking param: %S", n)
 		} else {
-					if n.Esc&EscContentEscapes != 0 {
-						Warnl(n.Pos, "leaking param content: %S", n)
-					}
-					for i := 0; i < numEscReturns; i++ {
-						if x := getEscReturn(n.Esc, i); x >= 0 {
-							res := n.Name.Curfn.Type.Results().Field(i).Sym
-							Warnl(n.Pos, "leaking param: %S to result %v level=%d", n, res, x)
-						}
-					}
-				}
+			if Debug['m'] != 0 && n.Op != ONAME && n.Op != OTYPESW && n.Op != ORANGE && n.Op != ODEFER {
+				Warnl(n.Pos, "%S %S does not escape", funcSym(loc.curfn), n)
 			}
-		} else {
 			n.Esc = EscNone
 			if loc.transient {
 				switch n.Op {
@@ -1307,10 +1298,6 @@ func (e *Escape) finish() {
 					n.SetNoescape(true)
 				}
 			}
-
-			if Debug['m'] != 0 && n.Op != ONAME && n.Op != OTYPESW && n.Op != ORANGE && n.Op != ODEFER {
-				Warnl(n.Pos, "%S %S does not escape", funcSym(loc.curfn), n)
-			}
 		}
 	}
 }

test/uintptrescapes2.go

@@ -18,7 +18,7 @@ func F1(a uintptr) {} // ERROR "escaping uintptr"
 
 //go:uintptrescapes
 //go:noinline
-func F2(a ...uintptr) {} // ERROR "escaping ...uintptr" "a does not escape"
+func F2(a ...uintptr) {} // ERROR "escaping ...uintptr"
 
 //go:uintptrescapes
 //go:noinline