runtime: eliminate some unnecessary uintptr conversions

arena_{start,used,end} are already uintptr, so no need to convert them
to uintptr, much less to convert them to unsafe.Pointer and then to
uintptr.  No binary change to pkg/linux_amd64/runtime.a.

Change-Id: Ia4232ed2a724c44fde7eba403c5fe8e6dccaa879
Reviewed-on: https://go-review.googlesource.com/16339Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>

src/runtime/malloc.go

@@ -388,7 +388,7 @@ func sysReserveHigh(n uintptr, reserved *bool) unsafe.Pointer {
 }
 
 func mHeap_SysAlloc(h *mheap, n uintptr) unsafe.Pointer {
-	if n > uintptr(h.arena_end)-uintptr(h.arena_used) {
+	if n > h.arena_end-h.arena_used {
 		// We are in 32-bit mode, maybe we didn't use all possible address space yet.
 		// Reserve some more space.
 		p_size := round(n+_PageSize, 256<<20)
@@ -420,7 +420,7 @@ func mHeap_SysAlloc(h *mheap, n uintptr) unsafe.Pointer {
 		}
 	}
 
-	if n <= uintptr(h.arena_end)-uintptr(h.arena_used) {
+	if n <= h.arena_end-h.arena_used {
 		// Keep taking from our reservation.
 		p := h.arena_used
 		sysMap(unsafe.Pointer(p), n, h.arena_reserved, &memstats.heap_sys)
@@ -438,7 +438,7 @@ func mHeap_SysAlloc(h *mheap, n uintptr) unsafe.Pointer {
 	}
 
 	// If using 64-bit, our reservation is all we have.
-	if uintptr(h.arena_end)-uintptr(h.arena_start) >= _MaxArena32 {
+	if h.arena_end-h.arena_start >= _MaxArena32 {
 		return nil
 	}
 
@@ -451,7 +451,7 @@ func mHeap_SysAlloc(h *mheap, n uintptr) unsafe.Pointer {
 		return nil
 	}
 
-	if p < h.arena_start || uintptr(p)+p_size-uintptr(h.arena_start) >= _MaxArena32 {
+	if p < h.arena_start || uintptr(p)+p_size-h.arena_start >= _MaxArena32 {
 		print("runtime: memory allocated by OS (", p, ") not in usable range [", hex(h.arena_start), ",", hex(h.arena_start+_MaxArena32), ")\n")
 		sysFree(unsafe.Pointer(p), p_size, &memstats.heap_sys)
 		return nil
@@ -459,7 +459,7 @@ func mHeap_SysAlloc(h *mheap, n uintptr) unsafe.Pointer {
 
 	p_end := p + p_size
 	p += -p & (_PageSize - 1)
-	if uintptr(p)+n > uintptr(h.arena_used) {
+	if uintptr(p)+n > h.arena_used {
 		mHeap_MapBits(h, p+n)
 		mHeap_MapSpans(h, p+n)
 		h.arena_used = p + n

src/runtime/mfinal.go

@@ -384,8 +384,8 @@ func findObject(v unsafe.Pointer) (s *mspan, x unsafe.Pointer, n uintptr) {
 	}
 
 	// find span
-	arena_start := uintptr(unsafe.Pointer(mheap_.arena_start))
-	arena_used := uintptr(unsafe.Pointer(mheap_.arena_used))
+	arena_start := mheap_.arena_start
+	arena_used := mheap_.arena_used
 	if uintptr(v) < arena_start || uintptr(v) >= arena_used {
 		return
 	}

src/runtime/mheap.go

@@ -581,7 +581,7 @@ HaveSpan:
 		mSpan_Init(t, s.start+pageID(npage), s.npages-npage)
 		s.npages = npage
 		p := uintptr(t.start)
-		p -= (uintptr(unsafe.Pointer(h.arena_start)) >> _PageShift)
+		p -= (h.arena_start >> _PageShift)
 		if p > 0 {
 			h_spans[p-1] = s
 		}
@@ -596,7 +596,7 @@ HaveSpan:
 	s.unusedsince = 0
 
 	p := uintptr(s.start)
-	p -= (uintptr(unsafe.Pointer(h.arena_start)) >> _PageShift)
+	p -= (h.arena_start >> _PageShift)
 	for n := uintptr(0); n < npage; n++ {
 		h_spans[p+n] = s
 	}
@@ -663,7 +663,7 @@ func mHeap_Grow(h *mheap, npage uintptr) bool {
 	s := (*mspan)(fixAlloc_Alloc(&h.spanalloc))
 	mSpan_Init(s, pageID(uintptr(v)>>_PageShift), ask>>_PageShift)
 	p := uintptr(s.start)
-	p -= (uintptr(unsafe.Pointer(h.arena_start)) >> _PageShift)
+	p -= (h.arena_start >> _PageShift)
 	for i := p; i < p+s.npages; i++ {
 		h_spans[i] = s
 	}
@@ -679,7 +679,7 @@ func mHeap_Grow(h *mheap, npage uintptr) bool {
 // and is guaranteed to be start or end of span.
 func mHeap_Lookup(h *mheap, v unsafe.Pointer) *mspan {
 	p := uintptr(v)
-	p -= uintptr(unsafe.Pointer(h.arena_start))
+	p -= h.arena_start
 	return h_spans[p>>_PageShift]
 }
 
@@ -691,12 +691,12 @@ func mHeap_Lookup(h *mheap, v unsafe.Pointer) *mspan {
 // other garbage in their middles, so we have to
 // check for that.
 func mHeap_LookupMaybe(h *mheap, v unsafe.Pointer) *mspan {
-	if uintptr(v) < uintptr(unsafe.Pointer(h.arena_start)) || uintptr(v) >= uintptr(unsafe.Pointer(h.arena_used)) {
+	if uintptr(v) < h.arena_start || uintptr(v) >= h.arena_used {
 		return nil
 	}
 	p := uintptr(v) >> _PageShift
 	q := p
-	q -= uintptr(unsafe.Pointer(h.arena_start)) >> _PageShift
+	q -= h.arena_start >> _PageShift
 	s := h_spans[q]
 	if s == nil || p < uintptr(s.start) || uintptr(v) >= uintptr(unsafe.Pointer(s.limit)) || s.state != _MSpanInUse {
 		return nil
@@ -779,7 +779,7 @@ func mHeap_FreeSpanLocked(h *mheap, s *mspan, acctinuse, acctidle bool, unusedsi
 
 	// Coalesce with earlier, later spans.
 	p := uintptr(s.start)
-	p -= uintptr(unsafe.Pointer(h.arena_start)) >> _PageShift
+	p -= h.arena_start >> _PageShift
 	if p > 0 {
 		t := h_spans[p-1]
 		if t != nil && t.state == _MSpanFree {