go/test/typeparam/issue44688.go
Keith Randall 301f6c8019 cmd/compile: keep methods on generic types from being deadcode eliminated
We currently make dictionaries contain a relocation pointing to
methods that generic code might use, so that those methods are not
deadcode eliminated. However, with inlining we can end up not using
the dictionary, making the reference from the dictionary to the method
no longer keep the method alive.

Fix this by keeping the dictionary alive at generic interface call sites.
It's a bit of overkill, as we only need to keep the dictionary statically
alive. We don't actually need it dynamically alive, which is what KeepAlive
does. But it works. It ends up generating a LEAQ + stack spill that aren't
necessary, but that's pretty low overhead.

To make this work, I needed to stop generating methods on shape types.
We should do this anyway, as we shouldn't ever need them. But currently
we do use them! issue44688.go has a test that only works because it calls
a method on a shape type. I've disabled that test for now, will work on it
in a subsequent CL.

Fixes #48047

Change-Id: I78968868d6486c1745f51b8b43be0898931432a2
Reviewed-on: https://go-review.googlesource.com/c/go/+/349169
Trust: Keith Randall <khr@golang.org>
Trust: Dan Scales <danscales@google.com>
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Dan Scales <danscales@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
2021-09-27 20:42:34 +00:00

149 lines
1.9 KiB
Go

// run -gcflags=-G=3
// Copyright 2021 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// derived & expanded from cmd/compile/internal/types2/testdata/fixedbugs/issue44688.go2
package main
type A1[T any] struct {
val T
}
func (p *A1[T]) m1(val T) {
p.val = val
}
type A2[T any] interface {
m2(T)
}
type B1[T any] struct {
filler int
*A1[T]
A2[T]
}
type B2[T any] interface {
A2[T]
}
type ImpA2[T any] struct {
f T
}
func (a2 *ImpA2[T]) m2(s T) {
a2.f = s
}
type C[T any] struct {
filler1 int
filler2 int
B1[T]
}
type D[T any] struct {
filler1 int
filler2 int
filler3 int
C[T]
}
func test1[T any](arg T) {
// calling embedded methods
var b1 B1[T]
b1.A1 = &A1[T]{}
b1.A2 = &ImpA2[T]{}
b1.A1.m1(arg)
b1.m1(arg)
b1.A2.m2(arg)
b1.m2(arg)
var b2 B2[T]
b2 = &ImpA2[T]{}
b2.m2(arg)
// a deeper nesting
var d D[T]
d.C.B1.A1 = &A1[T]{}
d.C.B1.A2 = &ImpA2[T]{}
d.m1(arg)
d.m2(arg)
// calling method expressions
m1x := B1[T].m1
m1x(b1, arg)
// TODO(khr): reenable these.
//m2x := B2[T].m2
//m2x(b2, arg)
// calling method values
m1v := b1.m1
m1v(arg)
m2v := b1.m2
m2v(arg)
b2v := b2.m2
b2v(arg)
}
func test2() {
// calling embedded methods
var b1 B1[string]
b1.A1 = &A1[string]{}
b1.A2 = &ImpA2[string]{}
b1.A1.m1("")
b1.m1("")
b1.A2.m2("")
b1.m2("")
var b2 B2[string]
b2 = &ImpA2[string]{}
b2.m2("")
// a deeper nesting
var d D[string]
d.C.B1.A1 = &A1[string]{}
d.C.B1.A2 = &ImpA2[string]{}
d.m1("")
d.m2("")
// calling method expressions
m1x := B1[string].m1
m1x(b1, "")
m2x := B2[string].m2
m2x(b2, "")
// calling method values
m1v := b1.m1
m1v("")
m2v := b1.m2
m2v("")
b2v := b2.m2
b2v("")
}
// actual test case from issue
type A[T any] struct{}
func (*A[T]) f(T) {}
type B[T any] struct{ A[T] }
func test3() {
var b B[string]
b.A.f("")
b.f("")
}
func main() {
test1[string]("")
test2()
test3()
}