cmd/dist, internal/abi: support bootstrapping with gccgo

The required gc bootstrap compiler, 1.17, has an internal/lazyregexp
package. It permits that package to be imported by internal/profile
while bootstrapping. The gccgo compiler also has an internal/lazyregexp
package, but it does not permit the gc compiler to import it.

Permit bootstrapping with gccgo by adding internal/lazyregexp to the
list of bootstrap directories.

The gccgo compiler recognizes the magic functions internal/abi.FuncPCABI0
and FuncPCABIInternal, but only in the internal/abi package, not
in the bootstrapping internal/abi package.

Permit bootstrapping with gccgo by adding definitions of those functions
with build tags so that they are only used by gccgo.

Fixes #60913

Change-Id: I3a78848d545db13314409d170d63f4cc737ca12e
Reviewed-on: https://go-review.googlesource.com/c/go/+/505036
Reviewed-by: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>

src/cmd/dist/buildtool.go

@@ -70,6 +70,11 @@ var bootstrapDirs = []string{
 	"internal/goexperiment",
 	"internal/goroot",
 	"internal/goversion",
+	// internal/lazyregexp is provided by Go 1.17, which permits it to
+	// be imported by other packages in this list, but is not provided
+	// by the Go 1.17 version of gccgo. It's on this list only to
+	// support gccgo, and can be removed if we require gccgo 14 or later.
+	"internal/lazyregexp",
 	"internal/pkgbits",
 	"internal/platform",
 	"internal/profile",

src/internal/abi/funcpc.go

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build !gccgo
+
 package abi
 
 // FuncPC* intrinsics.

src/internal/abi/funcpc_gccgo.go

@@ -0,0 +1,21 @@
+// Copyright 2023 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.
+
+// For bootstrapping with gccgo.
+
+//go:build gccgo
+
+package abi
+
+import "unsafe"
+
+func FuncPCABI0(f interface{}) uintptr {
+	words := (*[2]unsafe.Pointer)(unsafe.Pointer(&f))
+	return *(*uintptr)(unsafe.Pointer(words[1]))
+}
+
+func FuncPCABIInternal(f interface{}) uintptr {
+	words := (*[2]unsafe.Pointer)(unsafe.Pointer(&f))
+	return *(*uintptr)(unsafe.Pointer(words[1]))
+}