cmd/compile: remove trivial closure reference

Trivial closures will be converted to global functions, thus they are
not closures anymore. Using fn.IsClosure function is enough, allow
removing the trivial/non-trivial closures in the code.

Change-Id: Iceb186dd92c1732b101e221ebc13406db35c69ea
Reviewed-on: https://go-review.googlesource.com/c/go/+/611995
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Tim King <taking@google.com>
Auto-Submit: Cuong Manh Le <cuong.manhle.vn@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@google.com>

6 files changed, 16 insertions, 23 deletions

diff --git a/src/cmd/compile/internal/deadlocals/deadlocals.go b/src/cmd/compile/internal/deadlocals/deadlocals.go
index 8bc04b7ff0..238450416a 100644
--- a/src/cmd/compile/internal/deadlocals/deadlocals.go
+++ b/src/cmd/compile/internal/deadlocals/deadlocals.go
@@ -36,7 +36,7 @@ func Funcs(fns []*ir.Func) {
 				// Kludge for "missing func info" linker panic.
 				// See also closureInitLSym in inline/inl.go.
 				if clo, ok := (*as.rhs).(*ir.ClosureExpr); ok && clo.Op() == ir.OCLOSURE {
-					if !ir.IsTrivialClosure(clo) {
+					if clo.Func.IsClosure() {
 						ir.InitLSym(clo.Func, true)
 					}
 				}
diff --git a/src/cmd/compile/internal/inline/inl.go b/src/cmd/compile/internal/inline/inl.go
index c9b9e18eaf..9834737bfb 100644
--- a/src/cmd/compile/internal/inline/inl.go
+++ b/src/cmd/compile/internal/inline/inl.go
@@ -1020,7 +1020,7 @@ func mkinlcall(callerfn *ir.Func, n *ir.CallExpr, fn *ir.Func, bigCaller bool) *
 		// typecheck.Target.Decls (ir.UseClosure adds all closures to
 		// Decls).
 		//
-		// However, non-trivial closures in Decls are ignored, and are
+		// However, closures in Decls are ignored, and are
 		// instead enqueued when walk of the calling function
 		// discovers them.
 		//
@@ -1045,8 +1045,8 @@ func mkinlcall(callerfn *ir.Func, n *ir.CallExpr, fn *ir.Func, bigCaller bool) *
 		}
 
 		clo := n.Fun.(*ir.ClosureExpr)
-		if ir.IsTrivialClosure(clo) {
-			// enqueueFunc will handle trivial closures anyways.
+		if !clo.Func.IsClosure() {
+			// enqueueFunc will handle non closures anyways.
 			return
 		}
 
diff --git a/src/cmd/compile/internal/ir/func.go b/src/cmd/compile/internal/ir/func.go
index 0675150b2d..f9af358ef4 100644
--- a/src/cmd/compile/internal/ir/func.go
+++ b/src/cmd/compile/internal/ir/func.go
@@ -282,12 +282,12 @@ func (f *Func) SetWBPos(pos src.XPos) {
 	}
 }
 
+// IsClosure reports whether f is a function literal that captures at least one value.
 func (f *Func) IsClosure() bool {
 	if f.OClosure == nil {
 		return false
 	}
-	// Trivial closure will be converted to global.
-	return !IsTrivialClosure(f.OClosure)
+	return len(f.ClosureVars) > 0
 }
 
 // FuncName returns the name (without the package) of the function f.
@@ -419,12 +419,6 @@ func ClosureDebugRuntimeCheck(clo *ClosureExpr) {
 	}
 }
 
-// IsTrivialClosure reports whether closure clo has an
-// empty list of captured vars.
-func IsTrivialClosure(clo *ClosureExpr) bool {
-	return len(clo.Func.ClosureVars) == 0
-}
-
 // globClosgen is like Func.Closgen, but for the global scope.
 var globClosgen int32
 
diff --git a/src/cmd/compile/internal/ir/scc.go b/src/cmd/compile/internal/ir/scc.go
index 265dce251e..b6056040f7 100644
--- a/src/cmd/compile/internal/ir/scc.go
+++ b/src/cmd/compile/internal/ir/scc.go
@@ -14,7 +14,7 @@ package ir
 // The algorithm (known as Tarjan's algorithm) for doing that is taken from
 // Sedgewick, Algorithms, Second Edition, p. 482, with two adaptations.
 //
-// First, a non-trivial closure function (fn.OClosure != nil) cannot be
+// First, a closure function (fn.IsClosure()) cannot be
 // the root of a connected component. Refusing to use it as a root forces
 // it into the component of the function in which it appears.  This is
 // more convenient for escape analysis.
diff --git a/src/cmd/compile/internal/staticinit/sched.go b/src/cmd/compile/internal/staticinit/sched.go
index 56203120b2..66ef167d35 100644
--- a/src/cmd/compile/internal/staticinit/sched.go
+++ b/src/cmd/compile/internal/staticinit/sched.go
@@ -389,7 +389,7 @@ func (s *Schedule) StaticAssign(l *ir.Name, loff int64, r ir.Node, typ *types.Ty
 
 	case ir.OCLOSURE:
 		r := r.(*ir.ClosureExpr)
-		if ir.IsTrivialClosure(r) {
+		if !r.Func.IsClosure() {
 			if base.Debug.Closure > 0 {
 				base.WarnfAt(r.Pos(), "closure converted to global")
 			}
@@ -668,7 +668,7 @@ func (s *Schedule) staticAssignInlinedCall(l *ir.Name, loff int64, call *ir.Inli
 		count[x.(*ir.Name)] = 0
 	}
 
-	hasNonTrivialClosure := false
+	hasClosure := false
 	ir.Visit(as2body.Rhs[0], func(n ir.Node) {
 		if name, ok := n.(*ir.Name); ok {
 			if c, ok := count[name]; ok {
@@ -676,13 +676,13 @@ func (s *Schedule) staticAssignInlinedCall(l *ir.Name, loff int64, call *ir.Inli
 			}
 		}
 		if clo, ok := n.(*ir.ClosureExpr); ok {
-			hasNonTrivialClosure = hasNonTrivialClosure || !ir.IsTrivialClosure(clo)
+			hasClosure = hasClosure || clo.Func.IsClosure()
 		}
 	})
 
-	// If there's a non-trivial closure, it has captured the param,
+	// If there's a closure, it has captured the param,
 	// so we can't substitute arg for param.
-	if hasNonTrivialClosure {
+	if hasClosure {
 		return false
 	}
 
diff --git a/src/cmd/compile/internal/walk/closure.go b/src/cmd/compile/internal/walk/closure.go
index 38c6c03dc4..0abf5a0f06 100644
--- a/src/cmd/compile/internal/walk/closure.go
+++ b/src/cmd/compile/internal/walk/closure.go
@@ -33,7 +33,7 @@ func directClosureCall(n *ir.CallExpr) {
 	clo := n.Fun.(*ir.ClosureExpr)
 	clofn := clo.Func
 
-	if ir.IsTrivialClosure(clo) {
+	if !clofn.IsClosure() {
 		return // leave for walkClosure to handle
 	}
 
@@ -87,16 +87,15 @@ func directClosureCall(n *ir.CallExpr) {
 
 	// Add to Closures for enqueueFunc. It's no longer a proper
 	// closure, but we may have already skipped over it in the
-	// functions list as a non-trivial closure, so this just
-	// ensures it's compiled.
+	// functions list, so this just ensures it's compiled.
 	ir.CurFunc.Closures = append(ir.CurFunc.Closures, clofn)
 }
 
 func walkClosure(clo *ir.ClosureExpr, init *ir.Nodes) ir.Node {
 	clofn := clo.Func
 
-	// If no closure vars, don't bother wrapping.
-	if ir.IsTrivialClosure(clo) {
+	// If not a closure, don't bother wrapping.
+	if !clofn.IsClosure() {
 		if base.Debug.Closure > 0 {
 			base.WarnfAt(clo.Pos(), "closure converted to global")
 		}