09b7f36b2f
Remove fixed uses of X18. TEST=ci (Linux), speculative (Fuchsia) Change-Id: I20e31fc2ab7d44cbf02e591be92261067158509d Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/244943 Reviewed-by: Alexander Markov <alexmarkov@google.com> Commit-Queue: Ryan Macnak <rmacnak@google.com>