[dev.regabi] cmd/compile: remove CaptureVars

Capture analysis is now part of escape analysis.

Passes toolstash -cmp.

Change-Id: Ifcd3ecc342074c590e0db1ff0646dfa1ea2ff57b
Reviewed-on: https://go-review.googlesource.com/c/go/+/281543
Trust: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>

7 files changed, 14 insertions, 106 deletions

diff --git a/src/cmd/compile/internal/escape/escape.go b/src/cmd/compile/internal/escape/escape.go
index 4aa7381c20..2222f98003 100644
--- a/src/cmd/compile/internal/escape/escape.go
+++ b/src/cmd/compile/internal/escape/escape.go
@@ -361,9 +361,17 @@ func (b *batch) flowClosure(k hole, clo *ir.ClosureExpr, orphan bool) {
 		}
 
 		// Capture by value for variables <= 128 bytes that are never reassigned.
-		byval := !loc.addrtaken && !loc.reassigned && n.Type().Size() <= 128
-		if byval != n.Byval() {
-			base.FatalfAt(cv.Pos(), "byval mismatch: %v: %v != %v", cv, byval, n.Byval())
+		n.SetByval(!loc.addrtaken && !loc.reassigned && n.Type().Size() <= 128)
+		if !n.Byval() {
+			n.SetAddrtaken(true)
+		}
+
+		if base.Flag.LowerM > 1 {
+			how := "ref"
+			if n.Byval() {
+				how = "value"
+			}
+			base.WarnfAt(n.Pos(), "%v capturing by %s: %v (addr=%v assign=%v width=%d)", n.Curfn, how, n, loc.addrtaken, loc.reassigned, n.Type().Size())
 		}
 
 		// Flow captured variables to closure.
diff --git a/src/cmd/compile/internal/gc/main.go b/src/cmd/compile/internal/gc/main.go
index 2ea614e17f..c3756309ea 100644
--- a/src/cmd/compile/internal/gc/main.go
+++ b/src/cmd/compile/internal/gc/main.go
@@ -232,22 +232,6 @@ func Main(archInit func(*ssagen.ArchInfo)) {
 	}
 	typecheck.IncrementalAddrtaken = true
 
-	// Decide how to capture closed variables.
-	// This needs to run before escape analysis,
-	// because variables captured by value do not escape.
-	base.Timer.Start("fe", "capturevars")
-	for _, n := range typecheck.Target.Decls {
-		if n.Op() == ir.ODCLFUNC {
-			n := n.(*ir.Func)
-			if n.OClosure != nil {
-				ir.CurFunc = n
-				typecheck.CaptureVars(n)
-			}
-		}
-	}
-	typecheck.CaptureVarsComplete = true
-	ir.CurFunc = nil
-
 	if base.Debug.TypecheckInl != 0 {
 		// Typecheck imported function bodies if Debug.l > 1,
 		// otherwise lazily when used or re-exported.
diff --git a/src/cmd/compile/internal/ir/name.go b/src/cmd/compile/internal/ir/name.go
index 3999c0ecb4..a51cf79929 100644
--- a/src/cmd/compile/internal/ir/name.go
+++ b/src/cmd/compile/internal/ir/name.go
@@ -59,8 +59,7 @@ type Name struct {
 	// (results) are numbered starting at one, followed by function inputs
 	// (parameters), and then local variables. Vargen is used to distinguish
 	// local variables/params with the same name.
-	Vargen    int32
-	Decldepth int32 // declaration loop depth, increased for every loop or label
+	Vargen int32
 
 	Ntype    Ntype
 	Heapaddr *Name // temp holding heap address of param
@@ -260,15 +259,13 @@ func (n *Name) Alias() bool { return n.flags&nameAlias != 0 }
 func (n *Name) SetAlias(alias bool) { n.flags.set(nameAlias, alias) }
 
 const (
-	nameCaptured = 1 << iota // is the variable captured by a closure
-	nameReadonly
+	nameReadonly              = 1 << iota
 	nameByval                 // is the variable captured by value or by reference
 	nameNeedzero              // if it contains pointers, needs to be zeroed on function entry
 	nameAutoTemp              // is the variable a temporary (implies no dwarf info. reset if escapes to heap)
 	nameUsed                  // for variable declared and not used error
 	nameIsClosureVar          // PAUTOHEAP closure pseudo-variable; original at n.Name.Defn
 	nameIsOutputParamHeapAddr // pointer to a result parameter's heap copy
-	nameAssigned              // is the variable ever assigned to
 	nameAddrtaken             // address taken, even if not moved to heap
 	nameInlFormal             // PAUTO created by inliner, derived from callee formal
 	nameInlLocal              // PAUTO created by inliner, derived from callee local
@@ -277,28 +274,24 @@ const (
 	nameAlias                 // is type name an alias
 )
 
-func (n *Name) Captured() bool              { return n.flags&nameCaptured != 0 }
 func (n *Name) Readonly() bool              { return n.flags&nameReadonly != 0 }
 func (n *Name) Needzero() bool              { return n.flags&nameNeedzero != 0 }
 func (n *Name) AutoTemp() bool              { return n.flags&nameAutoTemp != 0 }
 func (n *Name) Used() bool                  { return n.flags&nameUsed != 0 }
 func (n *Name) IsClosureVar() bool          { return n.flags&nameIsClosureVar != 0 }
 func (n *Name) IsOutputParamHeapAddr() bool { return n.flags&nameIsOutputParamHeapAddr != 0 }
-func (n *Name) Assigned() bool              { return n.flags&nameAssigned != 0 }
 func (n *Name) Addrtaken() bool             { return n.flags&nameAddrtaken != 0 }
 func (n *Name) InlFormal() bool             { return n.flags&nameInlFormal != 0 }
 func (n *Name) InlLocal() bool              { return n.flags&nameInlLocal != 0 }
 func (n *Name) OpenDeferSlot() bool         { return n.flags&nameOpenDeferSlot != 0 }
 func (n *Name) LibfuzzerExtraCounter() bool { return n.flags&nameLibfuzzerExtraCounter != 0 }
 
-func (n *Name) SetCaptured(b bool)              { n.flags.set(nameCaptured, b) }
 func (n *Name) setReadonly(b bool)              { n.flags.set(nameReadonly, b) }
 func (n *Name) SetNeedzero(b bool)              { n.flags.set(nameNeedzero, b) }
 func (n *Name) SetAutoTemp(b bool)              { n.flags.set(nameAutoTemp, b) }
 func (n *Name) SetUsed(b bool)                  { n.flags.set(nameUsed, b) }
 func (n *Name) SetIsClosureVar(b bool)          { n.flags.set(nameIsClosureVar, b) }
 func (n *Name) SetIsOutputParamHeapAddr(b bool) { n.flags.set(nameIsOutputParamHeapAddr, b) }
-func (n *Name) SetAssigned(b bool)              { n.flags.set(nameAssigned, b) }
 func (n *Name) SetAddrtaken(b bool)             { n.flags.set(nameAddrtaken, b) }
 func (n *Name) SetInlFormal(b bool)             { n.flags.set(nameInlFormal, b) }
 func (n *Name) SetInlLocal(b bool)              { n.flags.set(nameInlLocal, b) }
diff --git a/src/cmd/compile/internal/ir/sizeof_test.go b/src/cmd/compile/internal/ir/sizeof_test.go
index 60120f2998..1a4d2e5c7a 100644
--- a/src/cmd/compile/internal/ir/sizeof_test.go
+++ b/src/cmd/compile/internal/ir/sizeof_test.go
@@ -21,7 +21,7 @@ func TestSizeof(t *testing.T) {
 		_64bit uintptr     // size on 64bit platforms
 	}{
 		{Func{}, 184, 320},
-		{Name{}, 124, 216},
+		{Name{}, 120, 216},
 	}
 
 	for _, tt := range tests {
diff --git a/src/cmd/compile/internal/typecheck/func.go b/src/cmd/compile/internal/typecheck/func.go
index 8fdb33b145..8789395ffb 100644
--- a/src/cmd/compile/internal/typecheck/func.go
+++ b/src/cmd/compile/internal/typecheck/func.go
@@ -100,32 +100,6 @@ func PartialCallType(n *ir.SelectorExpr) *types.Type {
 	return t
 }
 
-// CaptureVars is called in a separate phase after all typechecking is done.
-// It decides whether each variable captured by a closure should be captured
-// by value or by reference.
-// We use value capturing for values <= 128 bytes that are never reassigned
-// after capturing (effectively constant).
-func CaptureVars(fn *ir.Func) {
-	for _, v := range fn.ClosureVars {
-		outermost := v.Defn.(*ir.Name)
-
-		// out parameters will be assigned to implicitly upon return.
-		if outermost.Class != ir.PPARAMOUT && !outermost.Addrtaken() && !outermost.Assigned() && outermost.Type().Size() <= 128 {
-			outermost.SetByval(true)
-		} else {
-			outermost.SetAddrtaken(true)
-		}
-
-		if base.Flag.LowerM > 1 {
-			how := "ref"
-			if v.Byval() {
-				how = "value"
-			}
-			base.WarnfAt(v.Pos(), "%v capturing by %s: %v (addr=%v assign=%v width=%d)", v.Curfn, how, v, outermost.Addrtaken(), outermost.Assigned(), v.Type().Size())
-		}
-	}
-}
-
 // Lazy typechecking of imported bodies. For local functions, caninl will set ->typecheck
 // because they're a copy of an already checked body.
 func ImportedBody(fn *ir.Func) {
@@ -198,9 +172,6 @@ func fnpkg(fn *ir.Name) *types.Pkg {
 	return fn.Sym().Pkg
 }
 
-// CaptureVarsComplete is set to true when the capturevars phase is done.
-var CaptureVarsComplete bool
-
 // closurename generates a new unique name for a closure within
 // outerfunc.
 func closurename(outerfunc *ir.Func) *types.Sym {
@@ -336,22 +307,6 @@ func tcClosure(clo *ir.ClosureExpr, top int) {
 		return
 	}
 
-	for _, ln := range fn.ClosureVars {
-		n := ln.Defn
-		if !n.Name().Captured() {
-			n.Name().SetCaptured(true)
-			if n.Name().Decldepth == 0 {
-				base.Fatalf("typecheckclosure: var %v does not have decldepth assigned", n)
-			}
-
-			// Ignore assignments to the variable in straightline code
-			// preceding the first capturing by a closure.
-			if n.Name().Decldepth == decldepth {
-				n.Name().SetAssigned(false)
-			}
-		}
-	}
-
 	fn.Nname.SetSym(closurename(ir.CurFunc))
 	ir.MarkFunc(fn.Nname)
 	Func(fn)
@@ -363,10 +318,7 @@ func tcClosure(clo *ir.ClosureExpr, top int) {
 	if ir.CurFunc != nil && clo.Type() != nil {
 		oldfn := ir.CurFunc
 		ir.CurFunc = fn
-		olddd := decldepth
-		decldepth = 1
 		Stmts(fn.Body)
-		decldepth = olddd
 		ir.CurFunc = oldfn
 	}
 
@@ -400,12 +352,6 @@ func tcFunc(n *ir.Func) {
 		defer tracePrint("typecheckfunc", n)(nil)
 	}
 
-	for _, ln := range n.Dcl {
-		if ln.Op() == ir.ONAME && (ln.Class == ir.PPARAM || ln.Class == ir.PPARAMOUT) {
-			ln.Decldepth = 1
-		}
-	}
-
 	n.Nname = AssignExpr(n.Nname).(*ir.Name)
 	t := n.Nname.Type()
 	if t == nil {
diff --git a/src/cmd/compile/internal/typecheck/stmt.go b/src/cmd/compile/internal/typecheck/stmt.go
index d90d13b44c..8baa5dda78 100644
--- a/src/cmd/compile/internal/typecheck/stmt.go
+++ b/src/cmd/compile/internal/typecheck/stmt.go
@@ -228,7 +228,6 @@ func plural(n int) string {
 // tcFor typechecks an OFOR node.
 func tcFor(n *ir.ForStmt) ir.Node {
 	Stmts(n.Init())
-	decldepth++
 	n.Cond = Expr(n.Cond)
 	n.Cond = DefaultLit(n.Cond, nil)
 	if n.Cond != nil {
@@ -242,7 +241,6 @@ func tcFor(n *ir.ForStmt) ir.Node {
 		Stmts(n.Late)
 	}
 	Stmts(n.Body)
-	decldepth--
 	return n
 }
 
@@ -337,9 +335,7 @@ func tcRange(n *ir.RangeStmt) {
 		n.Value = AssignExpr(n.Value)
 	}
 
-	decldepth++
 	Stmts(n.Body)
-	decldepth--
 }
 
 // tcReturn typechecks an ORETURN node.
diff --git a/src/cmd/compile/internal/typecheck/typecheck.go b/src/cmd/compile/internal/typecheck/typecheck.go
index c3a5a3c40f..07bbd25105 100644
--- a/src/cmd/compile/internal/typecheck/typecheck.go
+++ b/src/cmd/compile/internal/typecheck/typecheck.go
@@ -21,8 +21,6 @@ var InitTodoFunc = ir.NewFunc(base.Pos)
 
 var inimport bool // set during import
 
-var decldepth int32
-
 var TypecheckAllowed bool
 
 var (
@@ -58,7 +56,6 @@ func Callee(n ir.Node) ir.Node {
 
 func FuncBody(n *ir.Func) {
 	ir.CurFunc = n
-	decldepth = 1
 	errorsBefore := base.Errors()
 	Stmts(n.Body)
 	CheckUnused(n)
@@ -506,9 +503,6 @@ func typecheck1(n ir.Node, top int) ir.Node {
 
 	case ir.ONAME:
 		n := n.(*ir.Name)
-		if n.Decldepth == 0 {
-			n.Decldepth = decldepth
-		}
 		if n.BuiltinOp != 0 {
 			if top&ctxCallee == 0 {
 				base.Errorf("use of builtin %v not in function call", n.Sym())
@@ -839,7 +833,6 @@ func typecheck1(n ir.Node, top int) ir.Node {
 		return n
 
 	case ir.OLABEL:
-		decldepth++
 		if n.Sym().IsBlank() {
 			// Empty identifier is valid but useless.
 			// Eliminate now to simplify life later.
@@ -1620,18 +1613,6 @@ func checkassign(stmt ir.Node, n ir.Node) {
 		return
 	}
 
-	// Variables declared in ORANGE are assigned on every iteration.
-	if !ir.DeclaredBy(n, stmt) || stmt.Op() == ir.ORANGE {
-		r := ir.OuterValue(n)
-		if r.Op() == ir.ONAME {
-			r := r.(*ir.Name)
-			r.SetAssigned(true)
-			if r.IsClosureVar() {
-				r.Defn.Name().SetAssigned(true)
-			}
-		}
-	}
-
 	if ir.IsAddressable(n) {
 		return
 	}