runtime: retype mheap.pagesInUse as atomic.Uint64

runtime: retype mheap.pagesInUse as atomic.Uint64

[git-generate]
cd src/runtime
mv export_test.go export.go
GOROOT=$(dirname $(dirname $PWD)) rf '
  add mheap.pagesInUse \
// Proportional sweep \
// \
// These parameters represent a linear function from gcController.heapLive \
// to page sweep count. The proportional sweep system works to \
// stay in the black by keeping the current page sweep count \
// above this line at the current gcController.heapLive. \
// \
// The line has slope sweepPagesPerByte and passes through a \
// basis point at (sweepHeapLiveBasis, pagesSweptBasis). At \
// any given time, the system is at (gcController.heapLive, \
// pagesSwept) in this space. \
// \
// It is important that the line pass through a point we \
// control rather than simply starting at a 0,0 origin \
// because that lets us adjust sweep pacing at any time while \
// accounting for current progress. If we could only adjust \
// the slope, it would create a discontinuity in debt if any \
// progress has already been made. \
pagesInUse_ atomic.Uint64 // pages of spans in stats mSpanInUse
  ex {
    import "runtime/internal/atomic"

    var t mheap
    var v, w uint64
    var d int64

    t.pagesInUse -> t.pagesInUse_.Load()
    t.pagesInUse = v -> t.pagesInUse_.Store(v)
    atomic.Load64(&t.pagesInUse) -> t.pagesInUse_.Load()
    atomic.LoadAcq64(&t.pagesInUse) -> t.pagesInUse_.LoadAcquire()
    atomic.Store64(&t.pagesInUse, v) -> t.pagesInUse_.Store(v)
    atomic.StoreRel64(&t.pagesInUse, v) -> t.pagesInUse_.StoreRelease(v)
    atomic.Cas64(&t.pagesInUse, v, w) -> t.pagesInUse_.CompareAndSwap(v, w)
    atomic.Xchg64(&t.pagesInUse, v) -> t.pagesInUse_.Swap(v)
    atomic.Xadd64(&t.pagesInUse, d) -> t.pagesInUse_.Add(d)
  }
  rm mheap.pagesInUse
  mv mheap.pagesInUse_ mheap.pagesInUse
'
mv export.go export_test.go

Change-Id: I495d188683dba0778518563c46755b5ad43be298
Reviewed-on: https://go-review.googlesource.com/c/go/+/356549
Trust: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Austin Clements <austin@google.com>