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[dev.typeparams] cmd/compile: refactor "need to emit" logic for types

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This CL refactors out a single reflectdata.NeedEmit function that
reports whether the current compilation unit needs to emit the runtime
type descriptor and method wrappers for a given type.

As a minor side bonus, this CL also skips compiling the "error.Error"
wrapper in non-runtime packages. Package runtime already
unconditionally emitted the runtime type descriptor for error, so we
just need to make sure it emits the wrapper and other packages don't.

Passes toolstash -cmp.

Change-Id: Ic9ea219dfba8a0a57f2f42f817bdff7618732bff
Reviewed-on: https://go-review.googlesource.com/c/go/+/330754
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 2021-06-24 11:31:56 -07:00
parent badb98364b
commit 3f1a517a45
1 changed files with 55 additions and 36 deletions
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91
src/cmd/compile/internal/reflectdata/reflect.go
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@ -927,29 +927,27 @@ func writeType(t *types.Type) *obj.LSym {
if t.IsPtr() && t.Sym() == nil && t.Elem().Sym() != nil {
tbase = t.Elem()
}
if tbase.Kind() == types.TFORW {
base.Fatalf("unresolved defined type: %v", tbase)
}
dupok := 0
if tbase.Sym() == nil {
if tbase.Sym() == nil { // TODO(mdempsky): Probably need DUPOK for instantiated types too.
dupok = obj.DUPOK
}
if base.Ctxt.Pkgpath != "runtime" || (tbase != types.Types[tbase.Kind()] && tbase != types.ByteType && tbase != types.RuneType && tbase != types.ErrorType) { // int, float, etc
// Named types from other files are defined only by those files.
// However, as an exception, we can write out instantiated types
// in the local package, even if they may be marked as part of
// another package (the package of their base generic type).
if tbase.Sym() != nil && tbase.Sym().Pkg != types.LocalPkg &&
!tbase.IsFullyInstantiated() {
if i := typecheck.BaseTypeIndex(t); i >= 0 {
lsym.Pkg = tbase.Sym().Pkg.Prefix
lsym.SymIdx = int32(i)
lsym.Set(obj.AttrIndexed, true)
}
return lsym
}
// TODO(mdempsky): Investigate whether this can happen.
if tbase.Kind() == types.TFORW {
return lsym
if !NeedEmit(tbase) {
if i := typecheck.BaseTypeIndex(t); i >= 0 {
lsym.Pkg = tbase.Sym().Pkg.Prefix
lsym.SymIdx = int32(i)
lsym.Set(obj.AttrIndexed, true)
}
// TODO(mdempsky): Investigate whether this still happens.
// If we know we don't need to emit code for a type,
// we should have a link-symbol index for it.
// See also TODO in NeedEmit.
return lsym
}
ot := 0
@ -1678,6 +1676,44 @@ func CollectPTabs() {
}
}
// NeedEmit reports whether typ is a type that we need to emit code
// for (e.g., runtime type descriptors, method wrappers).
func NeedEmit(typ *types.Type) bool {
// TODO(mdempsky): Export data should keep track of which anonymous
// and instantiated types were emitted, so at least downstream
// packages can skip re-emitting them.
//
// Perhaps we can just generalize the linker-symbol indexing to
// track the index of arbitrary types, not just defined types, and
// use its presence to detect this. The same idea would work for
// instantiated generic functions too.
switch sym := typ.Sym(); {
case sym == nil:
// Anonymous type; possibly never seen before or ever again.
// Need to emit to be safe (however, see TODO above).
return true
case sym.Pkg == types.LocalPkg:
// Local defined type; our responsibility.
return true
case base.Ctxt.Pkgpath == "runtime" && (sym.Pkg == types.BuiltinPkg || sym.Pkg == ir.Pkgs.Unsafe):
// Package runtime is responsible for including code for builtin
// types (predeclared and package unsafe).
return true
case typ.IsFullyInstantiated():
// Instantiated type; possibly instantiated with unique type arguments.
// Need to emit to be safe (however, see TODO above).
return true
default:
// Should have been emitted by an imported package.
return false
}
}
// Generate a wrapper function to convert from
// a receiver of type T to a receiver of type U.
// That is,
@ -1739,24 +1775,7 @@ func methodWrapper(rcvr *types.Type, method *types.Field, forItab bool) *obj.LSy
return lsym
}
// imported reports whether typ is a defined type that was declared
// in an imported package, and therefore must have been compiled in
// that package.
importedType := func(typ *types.Type) bool {
return typ.Sym() != nil && typ.Sym().Pkg != types.LocalPkg &&
// Exception: need wrapper for error.Error (#29304).
// TODO(mdempsky): Put this in package runtime, like we do for
// the type descriptors for predeclared types.
typ != types.ErrorType &&
// Exception: parameterized types may have been instantiated
// with new type arguments, so we don't assume they've been
// compiled before.
!typ.IsFullyInstantiated()
}
if importedType(rcvr) || rcvr.IsPtr() && importedType(rcvr.Elem()) {
if !NeedEmit(rcvr) || rcvr.IsPtr() && !NeedEmit(rcvr.Elem()) {
return lsym
}