// error message don't handle it as n:n mapping below.
	isCall := false
	if r == 1 {
		_, isCall = syntax.Unparen(orig_rhs[0]).(*syntax.CallExpr)
	}

	// If we have a n:n mapping from lhs variable to rhs expression,
	// each value can be assigned to its corresponding variable.
	if l == r && !isCall {
		var x operand
		for i, lhs := range lhs {
			desc := lhs.name

		// Ignore Args since they can't be autos.
		if v.Op.SymEffect() != SymNone && v.Op != OpArg {
			panic("unhandled op with sym effect")
		}

		if v.Uses == 0 && v.Op != OpNilCheck && !v.Op.IsCall() && !v.Op.HasSideEffects() || len(args) == 0 {
			// We need to keep nil checks even if they have no use.
			// Also keep calls and values that have side effects.
			return
		}

		s.nospill |= regMask(1) << r
	}
	return c
}

// isLeaf reports whether f performs any calls.
func isLeaf(f *Func) bool {
	for _, b := range f.Blocks {
		for _, v := range b.Values {
			if v.Op.IsCall() && !v.Op.IsTailCall() {
				// tail call is not counted as it does not save the return PC or need a frame
				return false
			}
		}
	}
	return true
}

	tailCall          bool   // is a tail call
	nilCheck          bool   // this op is a nil check on arg0
	faultOnNilArg0    bool   // this op will fault if arg0 is nil (and aux encodes a small offset)
	faultOnNilArg1    bool   // this op will fault if arg1 is nil (and aux encodes a small offset)
	hasSideEffects    bool   // for "reasons", not to be eliminated.  E.g., atomic store, #19182.

			aux := v.Aux.(*AuxNameOffset)
			sl := LocalSlot{N: aux.Name, Type: v.Type, Off: aux.Offset}
			// install slot in lookup table
			idx, _ := sc.lookup(sl)
			// add to f.NamedValues if not already present
			addToNV(v, sc.canonSlot(idx))
		} else if v.Op.IsCall() {
			// if we hit a call, we've gone too far.
			break
		}
	}

	# GOPATH with p1 in d2, p2 in d2
	env GOPATH=$WORK${/}d1${:}$WORK${/}d2

	# build & install p1
	env
	go install -i p1
	! stale p1
	! stale p2

	# modify p2 - p1 should appear stale
	cp $WORK/p2x.go $WORK/d2/src/p2/p2.go
	stale p1 p2

	# build & install p1 again
	go install -i p11
	! stale p1
	! stale p2

	-- $WORK/d1/src/p1/p1.go --
	package p1
	import "p2"

	// Because we overwrite the build action with the install action below,
	// a1 may already be an install action fetched from the "build" cache key,
	// and the caller just doesn't realize.
	if strings.HasSuffix(a1.Mode, "-install") {
		if a1.buggyInstall && mode == ModeInstall {
			//  Congratulations! The buggy install is now a proper install.
			a1.buggyInstall = false
		}
		return a1
	}

//
// The commands are:
//
//	banner         print installation banner
//	bootstrap      rebuild everything
//	clean          deletes all built files
//	env [-p]       print environment (-p: include $PATH)
//	install [dir]  install individual directory
//	list [-json]   list all supported platforms
//	test [-h]      run Go test(s)
//	version        print Go version

	// one iteration.
	for _, x := range xl {
		if x != nil {
			return false
		}
	}
	return true
}

// isAll reports whether the termlist xl represents the set of all types.
func (xl termlist) isAll() bool {
	// If there's a 𝓤 term, the entire list is 𝓤.
	// If the termlist is in normal form, this requires at most
	// one iteration.
	for _, x := range xl {

func IsTestFile(file string) bool {
	// We don't cover tests, only the code they test.
	return strings.HasSuffix(file, "_test.go")
}

// IsNull reports whether the path is a common name for the null device.
// It returns true for /dev/null on Unix, or NUL (case-insensitive) on Windows.
func IsNull(path string) bool {
	if path == os.DevNull {
		return true
	}
	if runtime.GOOS == "windows" {
		if strings.EqualFold(path, "NUL") {