[dev.link] all: merge branch 'master' into dev.link

Clean merge.

Change-Id: Ib773b0bc00fd99d494f9331c3613bcc8285e48e3

src/runtime/runtime2.go

@@ -329,7 +329,7 @@ type gobuf struct {
 	ctxt unsafe.Pointer
 	ret  sys.Uintreg
 	lr   uintptr
-	bp   uintptr // for GOEXPERIMENT=framepointer
+	bp   uintptr // for framepointer-enabled architectures
 }
 
 // sudog represents a g in a wait list, such as for sending/receiving
@@ -910,15 +910,12 @@ type _defer struct {
 
 // A _panic holds information about an active panic.
 //
-// This is marked go:notinheap because _panic values must only ever
-// live on the stack.
+// A _panic value must only ever live on the stack.
 //
 // The argp and link fields are stack pointers, but don't need special
 // handling during stack growth: because they are pointer-typed and
 // _panic values only live on the stack, regular stack pointer
 // adjustment takes care of them.
-//
-//go:notinheap
 type _panic struct {
 	argp      unsafe.Pointer // pointer to arguments of deferred call run during panic; cannot move - known to liblink
 	arg       interface{}    // argument to panic
@@ -1050,8 +1047,7 @@ var (
 	isIntel              bool
 	lfenceBeforeRdtsc    bool
 
-	goarm                uint8 // set by cmd/link on arm systems
-	framepointer_enabled bool  // set by cmd/link
+	goarm uint8 // set by cmd/link on arm systems
 )
 
 // Set by the linker so the runtime can determine the buildmode.
@@ -1059,3 +1055,6 @@ var (
 	islibrary bool // -buildmode=c-shared
 	isarchive bool // -buildmode=c-archive
 )
+
+// Must agree with cmd/internal/objabi.Framepointer_enabled.
+const framepointer_enabled = GOARCH == "amd64" || GOARCH == "arm64" && (GOOS == "linux" || GOOS == "darwin")