// fits in a word.
	if minSizeForMallocHeader/goarch.PtrSize > 8*goarch.PtrSize {
		throw("max pointer/scan bitmap size for headerless objects is too large")
	}

	if minTagBits > taggedPointerBits {
		throw("taggedPointerbits too small")
	}

	// Initialize the heap.
	mheap_.init()
	mcache0 = allocmcache()
	lockInit(&gcBitsArenas.lock, lockRankGcBitsArenas)