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[dev.typeparams] cmd/compile: simplify variable capturing in unified IR

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While initially building out unified IR, I didn't have any indexing
scheme. Everything was written out in order. Consequently, if I wanted
to write A before B, I had to compute A before B.

One particular example of this is handling closure variables: the
reader needs the list of closure variables before it can start reading
the function body, so I had to write them out first, and so I had to
compute them first in a separate, dedicated pass.

However, that constraint went away a while ago. For example, it's now
possible to replace the two-pass closure variable capture with a
single pass. We just write out the function body earlier, but then
wait to write out its index.

I anticipate this approach will make it easier to implement
dictionaries: rather than needing a separate pass to correctly
recognize and handle all of the generics cases, we can just hook into
the existing logic.

Change-Id: Iab1e07f9202cd5d2b6864eef10116960456214df
Reviewed-on: https://go-review.googlesource.com/c/go/+/330851
Trust: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
This commit is contained in:
Matthew Dempsky 2021-06-25 01:54:50 -07:00
parent 9fe7c38d3d
commit 1b60284c0a
3 changed files with 80 additions and 199 deletions
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2
src/cmd/compile/internal/noder/linker.go
View file

@ -209,8 +209,6 @@ func (l *linker) relocFuncExt(w *encoder, name *ir.Name) {
pri, ok := bodyReader[name.Func]
assert(ok)
w.sync(syncAddBody)
w.sync(syncImplicitTypes)
w.reloc(relocBody, l.relocIdx(pri.pr, relocBody, pri.idx))
}

54
src/cmd/compile/internal/noder/reader.go
View file

@ -105,8 +105,9 @@ type reader struct {
// separately so that it doesn't take up space in every reader
// instance.
curfn *ir.Func
locals []*ir.Name
curfn *ir.Func
locals []*ir.Name
closureVars []*ir.Name
funarghack bool
@ -775,10 +776,10 @@ func (r *reader) funcExt(name *ir.Name) {
Cost: int32(r.len()),
CanDelayResults: r.bool(),
}
r.addBody(name.Func)
r.addBody(name.Func, r.explicits)
}
} else {
r.addBody(name.Func)
r.addBody(name.Func, r.explicits)
}
r.sync(syncEOF)
}
@ -840,25 +841,7 @@ var bodyReader = map[*ir.Func]pkgReaderIndex{}
// constructed.
var todoBodies []*ir.Func
// Keep in sync with writer.implicitTypes
// Also see comment there for why r.implicits and r.explicits should
// never both be non-empty.
func (r *reader) implicitTypes() []*types.Type {
r.sync(syncImplicitTypes)
implicits := r.implicits
if len(implicits) == 0 {
implicits = r.explicits
} else {
assert(len(r.explicits) == 0)
}
return implicits
}
func (r *reader) addBody(fn *ir.Func) {
r.sync(syncAddBody)
implicits := r.implicitTypes()
func (r *reader) addBody(fn *ir.Func, implicits []*types.Type) {
pri := pkgReaderIndex{r.p, r.reloc(relocBody), implicits}
bodyReader[fn] = pri
@ -877,7 +860,7 @@ func (pri pkgReaderIndex) funcBody(fn *ir.Func) {
func (r *reader) funcBody(fn *ir.Func) {
r.curfn = fn
r.locals = fn.ClosureVars
r.closureVars = fn.ClosureVars
// TODO(mdempsky): Get rid of uses of typecheck.NodAddrAt so we
// don't have to set ir.CurFunc.
@ -1004,7 +987,10 @@ func (r *reader) addLocal(name *ir.Name, ctxt ir.Class) {
func (r *reader) useLocal() *ir.Name {
r.sync(syncUseObjLocal)
return r.locals[r.len()]
if r.bool() {
return r.locals[r.len()]
}
return r.closureVars[r.len()]
}
func (r *reader) openScope() {
@ -1088,8 +1074,11 @@ func (r *reader) stmt1(tag codeStmt, out *ir.Nodes) ir.Node {
case stmtAssign:
pos := r.pos()
names, lhs := r.assignList()
// TODO(mdempsky): After quirks mode is gone, swap these
// statements so we visit LHS before RHS again.
rhs := r.exprList()
names, lhs := r.assignList()
if len(rhs) == 0 {
for _, name := range names {
@ -1225,8 +1214,12 @@ func (r *reader) forStmt(label *types.Sym) ir.Node {
if r.bool() {
pos := r.pos()
names, lhs := r.assignList()
// TODO(mdempsky): After quirks mode is gone, swap these
// statements so we read LHS before X again.
x := r.expr()
names, lhs := r.assignList()
body := r.blockStmt()
r.closeAnotherScope()
@ -1572,7 +1565,7 @@ func (r *reader) funcLit() ir.Node {
r.setType(cv, outer.Type())
}
r.addBody(fn)
r.addBody(fn, r.implicits)
return fn.OClosure
}
@ -1777,8 +1770,9 @@ func InlineCall(call *ir.CallExpr, fn *ir.Func, inlIndex int) *ir.InlinedCallExp
r.inlTreeIndex = inlIndex
r.inlPosBases = make(map[*src.PosBase]*src.PosBase)
for _, cv := range r.inlFunc.ClosureVars {
r.locals = append(r.locals, cv.Outer)
r.closureVars = make([]*ir.Name, len(r.inlFunc.ClosureVars))
for i, cv := range r.inlFunc.ClosureVars {
r.closureVars[i] = cv.Outer
}
r.funcargs(fn)

223
src/cmd/compile/internal/noder/writer.go
View file

@ -97,7 +97,10 @@ type writer struct {
explicitIdx map[*types2.TypeParam]int
// variables declared within this function
localsIdx map[types2.Object]int
localsIdx map[*types2.Var]int
closureVars []posObj
closureVarsIdx map[*types2.Var]int
}
func (pw *pkgWriter) newWriter(k reloc, marker syncMarker) *writer {
@ -626,11 +629,15 @@ func (w *writer) funcExt(obj *types2.Func) {
}
}
sig, block := obj.Type().(*types2.Signature), decl.Body
body, closureVars := w.p.bodyIdx(w.p.curpkg, sig, block, w.explicitIdx)
assert(len(closureVars) == 0)
w.sync(syncFuncExt)
w.pragmaFlag(pragma)
w.linkname(obj)
w.bool(false) // stub extension
w.addBody(obj.Type().(*types2.Signature), decl.Body, make(map[types2.Object]int))
w.reloc(relocBody, body)
w.sync(syncEOF)
}
@ -665,41 +672,9 @@ func (w *writer) pragmaFlag(p ir.PragmaFlag) {
// @@@ Function bodies
func (w *writer) implicitTypes() map[*types2.TypeParam]int {
w.sync(syncImplicitTypes)
// TODO(mdempsky): Theoretically, I think at this point we want to
// extend the implicit type parameters list with any new explicit
// type parameters.
//
// However, I believe that's moot: declared functions and methods
// have explicit type parameters, but are always declared at package
// scope (which has no implicit type parameters); and function
// literals can appear within a type-parameterized function (i.e.,
// implicit type parameters), but cannot have explicit type
// parameters of their own.
//
// So I think it's safe to just use whichever is non-empty.
implicitIdx := w.implicitIdx
if len(implicitIdx) == 0 {
implicitIdx = w.explicitIdx
} else {
assert(len(w.explicitIdx) == 0)
}
return implicitIdx
}
func (w *writer) addBody(sig *types2.Signature, block *syntax.BlockStmt, localsIdx map[types2.Object]int) {
w.sync(syncAddBody)
implicits := w.implicitTypes()
w.reloc(relocBody, w.p.bodyIdx(w.p.curpkg, sig, block, implicits, localsIdx))
}
func (pw *pkgWriter) bodyIdx(pkg *types2.Package, sig *types2.Signature, block *syntax.BlockStmt, implicitIdx map[*types2.TypeParam]int, localsIdx map[types2.Object]int) int {
func (pw *pkgWriter) bodyIdx(pkg *types2.Package, sig *types2.Signature, block *syntax.BlockStmt, implicitIdx map[*types2.TypeParam]int) (idx int, closureVars []posObj) {
w := pw.newWriter(relocBody, syncFuncBody)
w.implicitIdx = implicitIdx
w.localsIdx = localsIdx
w.funcargs(sig)
if w.bool(block != nil) {
@ -707,7 +682,7 @@ func (pw *pkgWriter) bodyIdx(pkg *types2.Package, sig *types2.Signature, block *
w.pos(block.Rbrace)
}
return w.flush()
return w.flush(), w.closureVars
}
func (w *writer) funcargs(sig *types2.Signature) {
@ -730,19 +705,35 @@ func (w *writer) funcarg(param *types2.Var, result bool) {
}
}
func (w *writer) addLocal(obj types2.Object) {
func (w *writer) addLocal(obj *types2.Var) {
w.sync(syncAddLocal)
idx := len(w.localsIdx)
if enableSync {
w.int(idx)
}
if w.localsIdx == nil {
w.localsIdx = make(map[*types2.Var]int)
}
w.localsIdx[obj] = idx
}
func (w *writer) useLocal(obj types2.Object) {
func (w *writer) useLocal(pos syntax.Pos, obj *types2.Var) {
w.sync(syncUseObjLocal)
idx, ok := w.localsIdx[obj]
assert(ok)
if idx, ok := w.localsIdx[obj]; w.bool(ok) {
w.len(idx)
return
}
idx, ok := w.closureVarsIdx[obj]
if !ok {
if w.closureVarsIdx == nil {
w.closureVarsIdx = make(map[*types2.Var]int)
}
idx = len(w.closureVars)
w.closureVars = append(w.closureVars, posObj{pos, obj})
w.closureVarsIdx[obj] = idx
}
w.len(idx)
}
@ -806,8 +797,8 @@ func (w *writer) stmt1(stmt syntax.Stmt) {
default:
w.code(stmtAssign)
w.pos(stmt)
w.assignList(stmt.Lhs)
w.exprList(stmt.Rhs)
w.assignList(stmt.Lhs)
}
case *syntax.BlockStmt:
@ -877,6 +868,8 @@ func (w *writer) assignList(expr syntax.Expr) {
for _, expr := range exprs {
if name, ok := expr.(*syntax.Name); ok && name.Value != "_" {
if obj, ok := w.p.info.Defs[name]; ok {
obj := obj.(*types2.Var)
w.bool(true)
w.pos(obj)
w.localIdent(obj)
@ -923,16 +916,16 @@ func (w *writer) declStmt(decl syntax.Decl) {
for i, name := range decl.NameList {
w.code(stmtAssign)
w.pos(decl)
w.assignList(name)
w.exprList(values[i])
w.assignList(name)
}
break
}
w.code(stmtAssign)
w.pos(decl)
w.assignList(namesAsExpr(decl.NameList))
w.exprList(decl.Values)
w.assignList(namesAsExpr(decl.NameList))
}
}
@ -949,8 +942,8 @@ func (w *writer) forStmt(stmt *syntax.ForStmt) {
if rang, ok := stmt.Init.(*syntax.RangeClause); w.bool(ok) {
w.pos(rang)
w.assignList(rang.Lhs)
w.expr(rang.X)
w.assignList(rang.Lhs)
} else {
w.pos(stmt)
w.stmt(stmt.Init)
@ -1092,15 +1085,17 @@ func (w *writer) expr(expr syntax.Expr) {
}
if obj != nil {
if _, ok := w.localsIdx[obj]; ok {
assert(len(targs) == 0)
w.code(exprLocal)
w.useLocal(obj)
if isGlobal(obj) {
w.code(exprName)
w.obj(obj, targs)
return
}
w.code(exprName)
w.obj(obj, targs)
obj := obj.(*types2.Var)
assert(len(targs) == 0)
w.code(exprLocal)
w.useLocal(expr.Pos(), obj)
return
}
@ -1248,130 +1243,24 @@ func (w *writer) funcLit(expr *syntax.FuncLit) {
w.pos(expr.Type) // for QuirksMode
w.signature(sig)
closureVars, localsIdx := w.captureVars(expr)
block := expr.Body
body, closureVars := w.p.bodyIdx(w.p.curpkg, sig, block, w.implicitIdx)
w.len(len(closureVars))
for _, closureVar := range closureVars {
w.pos(closureVar.pos)
w.useLocal(closureVar.obj)
for _, cv := range closureVars {
w.pos(cv.pos)
if quirksMode() {
cv.pos = expr.Body.Rbrace
}
w.useLocal(cv.pos, cv.obj)
}
w.addBody(sig, expr.Body, localsIdx)
w.reloc(relocBody, body)
}
type posObj struct {
pos syntax.Pos
obj types2.Object
}
// captureVars returns the free variables used by the given function
// literal. The closureVars result is the list of free variables
// captured by expr, and localsIdx is a map from free variable to
// index. See varCaptor's identically named fields for more details.
func (w *writer) captureVars(expr *syntax.FuncLit) (closureVars []posObj, localsIdx map[types2.Object]int) {
scope, ok := w.p.info.Scopes[expr.Type]
assert(ok)
// TODO(mdempsky): This code needs to be cleaned up (e.g., to avoid
// traversing nested function literals multiple times). This will be
// easier after we drop quirks mode.
v := varCaptor{
w: w,
scope: scope,
localsIdx: make(map[types2.Object]int),
}
syntax.Walk(expr.Body, &v)
return v.closureVars, v.localsIdx
}
// varCaptor implements syntax.Visitor for enumerating free variables
// used by a function literal.
type varCaptor struct {
w *writer
scope *types2.Scope
// closureVars lists free variables along with the position where
// they first appeared, in order of appearance.
closureVars []posObj
// localsIdx is a map from free variables to their index within
// closureVars.
localsIdx map[types2.Object]int
}
func (v *varCaptor) capture(n *syntax.Name) {
obj, ok := v.w.p.info.Uses[n].(*types2.Var)
if !ok || obj.IsField() {
return // not a variable
}
if obj.Parent() == obj.Pkg().Scope() {
return // global variable
}
if _, ok := v.localsIdx[obj]; ok {
return // already captured
}
for parent := obj.Parent(); parent != obj.Pkg().Scope(); parent = parent.Parent() {
if parent == v.scope {
return // object declared within our scope
}
}
idx := len(v.closureVars)
v.closureVars = append(v.closureVars, posObj{n.Pos(), obj})
v.localsIdx[obj] = idx
}
func (v *varCaptor) Visit(n syntax.Node) syntax.Visitor {
// Constant expressions don't count towards capturing.
if n, ok := n.(syntax.Expr); ok {
if tv, ok := v.w.p.info.Types[n]; ok && tv.Value != nil {
return nil
}
}
if n, ok := n.(*syntax.Name); ok {
v.capture(n)
}
if quirksMode() {
switch n := n.(type) {
case *syntax.FuncLit:
// Quirk: typecheck uses the rbrace position position of the
// function literal as the position of the intermediary capture.
end := len(v.closureVars)
syntax.Walk(n.Type, v) // unnecessary to walk, but consistent with non-quirks mode
syntax.Walk(n.Body, v)
for i := end; i < len(v.closureVars); i++ {
v.closureVars[i].pos = n.Body.Rbrace
}
return nil
case *syntax.AssignStmt:
// Quirk: typecheck visits (and thus captures) the RHS of
// assignment statements (but not op= statements) before the LHS.
if n.Op == 0 || n.Op == syntax.Def {
syntax.Walk(n.Rhs, v)
syntax.Walk(n.Lhs, v)
return nil
}
case *syntax.RangeClause:
// Quirk: Similarly, typecheck visits the expression to be
// iterated over before the iteration variables.
syntax.Walk(n.X, v)
if n.Lhs != nil {
syntax.Walk(n.Lhs, v)
}
return nil
}
}
return v
obj *types2.Var
}
func (w *writer) exprList(expr syntax.Expr) {