cmd/compile: compute XOR's limits from argument's limits

This help to optimize code like this:

  func f(buckets *[512]bucket, v value) {
    a, b := v.computeSomething()
    // assume a and b are proved < 512
    b := &buckets[a ^ b] // pick a random bucket
    b.store(v)
  }

Change-Id: I1acf702f5a8137f9ded49081b4703922879b0288
Reviewed-on: https://go-review.googlesource.com/c/go/+/604455
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

0 files changed, 0 insertions, 0 deletions