cmd/compile: don't inline runtime functions in -d=checkptr build

Runtime functions, e.g. internal/abi.NoEscape, should not be
instrumented with checkptr. But if they are inlined into a
checkptr-enabled function, they will be instrumented, and may
result in a check failure.

Let the compiler not inline runtime functions into checkptr-
enabled functions.

Also undo the change in the strings package in CL 598295, as the
compiler handles it now.

Fixes #68511.
Updates #68415.

Change-Id: I78eb380855ac9dd53c1a1a628ec0da75c3e5a1a0
Reviewed-on: https://go-review.googlesource.com/c/go/+/599435
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Keith Randall <khr@google.com>

src/cmd/compile/internal/inline/inl.go

@@ -1007,6 +1007,15 @@ func canInlineCallExpr(callerfn *ir.Func, n *ir.CallExpr, callee *ir.Func, bigCa
 		return false, 0, false
 	}
 
+	if base.Debug.Checkptr != 0 && types.IsRuntimePkg(callee.Sym().Pkg) {
+		// We don't intrument runtime packages for checkptr (see base/flag.go).
+		if log && logopt.Enabled() {
+			logopt.LogOpt(n.Pos(), "cannotInlineCall", "inline", ir.FuncName(callerfn),
+				fmt.Sprintf(`call to into runtime package function %s in -d=checkptr build`, ir.PkgFuncName(callee)))
+		}
+		return false, 0, false
+	}
+
 	// Check if we've already inlined this function at this particular
 	// call site, in order to stop inlining when we reach the beginning
 	// of a recursion cycle again. We don't inline immediately recursive

src/cmd/compile/internal/types/type.go

@@ -1927,6 +1927,11 @@ func IsNoRacePkg(p *Pkg) bool {
 	return objabi.LookupPkgSpecial(p.Path).NoRaceFunc
 }
 
+// IsRuntimePkg reports whether p is a runtime package.
+func IsRuntimePkg(p *Pkg) bool {
+	return objabi.LookupPkgSpecial(p.Path).Runtime
+}
+
 // ReceiverBaseType returns the underlying type, if any,
 // that owns methods with receiver parameter t.
 // The result is either a named type or an anonymous struct.

src/cmd/internal/objabi/pkgspecial.go

@@ -18,6 +18,8 @@ type PkgSpecial struct {
 	//
 	// - Optimizations are always enabled.
 	//
+	// - Checkptr is always disabled.
+	//
 	// This should be set for runtime and all packages it imports, and may be
 	// set for additional packages.
 	Runtime bool

src/strings/builder.go

@@ -23,18 +23,6 @@ type Builder struct {
 	buf []byte
 }
 
-// This is just a wrapper around abi.NoEscape.
-//
-// This wrapper is necessary because internal/abi is a runtime package,
-// so it can not be built with -d=checkptr, causing incorrect inlining
-// decision when building with checkptr enabled, see issue #68415.
-//
-//go:nosplit
-//go:nocheckptr
-func noescape(p unsafe.Pointer) unsafe.Pointer {
-	return abi.NoEscape(p)
-}
-
 func (b *Builder) copyCheck() {
 	if b.addr == nil {
 		// This hack works around a failing of Go's escape analysis
@@ -42,7 +30,7 @@ func (b *Builder) copyCheck() {
 		// See issue 23382.
 		// TODO: once issue 7921 is fixed, this should be reverted to
 		// just "b.addr = b".
-		b.addr = (*Builder)(noescape(unsafe.Pointer(b)))
+		b.addr = (*Builder)(abi.NoEscape(unsafe.Pointer(b)))
 	} else if b.addr != b {
 		panic("strings: illegal use of non-zero Builder copied by value")
 	}

test/fixedbugs/issue68415.go

@@ -6,10 +6,14 @@
 
 package main
 
-import "regexp"
+import (
+	"regexp"
+	"unique"
+)
 
 var dataFileRegexp = regexp.MustCompile(`^data\.\d+\.bin$`)
 
 func main() {
 	_ = dataFileRegexp
+	unique.Make("")
 }