Golang Go语言中 sync.Map tryLoadOrStore 函数看不懂其中的 ic := i

// tryLoadOrStore atomically loads or stores a value if the entry is not
// expunged.
//
// If the entry is expunged, tryLoadOrStore leaves the entry unchanged and
// returns with ok==false.
func (e *entry) tryLoadOrStore(i interface{}) (actual interface{}, loaded, ok bool) {
p := atomic.LoadPointer(&e.p)
if p == expunged {
return nil, false, false
}
if p != nil {
return *(*interface{})§, true, true
}

// Copy the interface after the first load to make this method more amenable
// to escape analysis: if we hit the "load" path or the entry is expunged, we
// shouldn't bother heap-allocating.
ic := i
for {
	if atomic.CompareAndSwapPointer(&e.p, nil, unsafe.Pointer(&ic)) {
		return i, false, true
	}
	p = atomic.LoadPointer(&e.p)
	if p == expunged {
		return nil, false, false
	}
	if p != nil {
		return *(*interface{})(p), true, true
	}
}
}

为什么不用 ic := i 就会去堆上申请内存呢? 有巨佬或者彦祖知道吗~

整个函数感觉可以直接都放在 for 循环中，为什么要把前两个 if 判断单独拿出来？是因为放在 for 循环外有更好的性能吗