runtime: remove wbufptr

Since workbuf is now marked go:notinheap, the write barrier-preventing
wrapper type wbufptr is no longer necessary. Remove it.

Change-Id: I3e5b5803a1547d65de1c1a9c22458a38e08549b7
Reviewed-on: https://go-review.googlesource.com/35971
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>

diff --git a/src/runtime/mgcwork.go b/src/runtime/mgcwork.go
index 5eb05a767c055302960465094cd03ac20b539334..ef2453039f4f8e799039e7c4d007350964f3b270 100644 (file)
--- a/src/runtime/mgcwork.go
+++ b/src/runtime/mgcwork.go
@@ -25,21 +25,6 @@ const (
 // grey objects, thus blackening them, and then scans them,
 // potentially producing new pointers to grey objects.
 
-// A wbufptr holds a workbuf*, but protects it from write barriers.
-// workbufs never live on the heap, so write barriers are unnecessary.
-// Write barriers on workbuf pointers may also be dangerous in the GC.
-//
-// TODO: Since workbuf is now go:notinheap, this isn't necessary.
-type wbufptr uintptr
-
-func wbufptrOf(w *workbuf) wbufptr {
-       return wbufptr(unsafe.Pointer(w))
-}
-
-func (wp wbufptr) ptr() *workbuf {
-       return (*workbuf)(unsafe.Pointer(wp))
-}
-
 // A gcWork provides the interface to produce and consume work for the
 // garbage collector.
 //
@@ -75,7 +60,7 @@ type gcWork struct {
        // next.
        //
        // Invariant: Both wbuf1 and wbuf2 are nil or neither are.
-       wbuf1, wbuf2 wbufptr
+       wbuf1, wbuf2 *workbuf
 
        // Bytes marked (blackened) on this gcWork. This is aggregated
        // into work.bytesMarked by dispose.
@@ -87,12 +72,12 @@ type gcWork struct {
 }
 
 func (w *gcWork) init() {
-       w.wbuf1 = wbufptrOf(getempty())
+       w.wbuf1 = getempty()
        wbuf2 := trygetfull()
        if wbuf2 == nil {
                wbuf2 = getempty()
        }
-       w.wbuf2 = wbufptrOf(wbuf2)
+       w.wbuf2 = wbuf2
 }
 
 // put enqueues a pointer for the garbage collector to trace.
@@ -100,18 +85,18 @@ func (w *gcWork) init() {
 //go:nowritebarrier
 func (w *gcWork) put(obj uintptr) {
        flushed := false
-       wbuf := w.wbuf1.ptr()
+       wbuf := w.wbuf1
        if wbuf == nil {
                w.init()
-               wbuf = w.wbuf1.ptr()
+               wbuf = w.wbuf1
                // wbuf is empty at this point.
        } else if wbuf.nobj == len(wbuf.obj) {
                w.wbuf1, w.wbuf2 = w.wbuf2, w.wbuf1
-               wbuf = w.wbuf1.ptr()
+               wbuf = w.wbuf1
                if wbuf.nobj == len(wbuf.obj) {
                        putfull(wbuf)
                        wbuf = getempty()
-                       w.wbuf1 = wbufptrOf(wbuf)
+                       w.wbuf1 = wbuf
                        flushed = true
                }
        }
@@ -132,7 +117,7 @@ func (w *gcWork) put(obj uintptr) {
 // otherwise it returns false and the caller needs to call put.
 //go:nowritebarrier
 func (w *gcWork) putFast(obj uintptr) bool {
-       wbuf := w.wbuf1.ptr()
+       wbuf := w.wbuf1
        if wbuf == nil {
                return false
        } else if wbuf.nobj == len(wbuf.obj) {
@@ -151,15 +136,15 @@ func (w *gcWork) putFast(obj uintptr) bool {
 // other gcWork instances or other caches.
 //go:nowritebarrier
 func (w *gcWork) tryGet() uintptr {
-       wbuf := w.wbuf1.ptr()
+       wbuf := w.wbuf1
        if wbuf == nil {
                w.init()
-               wbuf = w.wbuf1.ptr()
+               wbuf = w.wbuf1
                // wbuf is empty at this point.
        }
        if wbuf.nobj == 0 {
                w.wbuf1, w.wbuf2 = w.wbuf2, w.wbuf1
-               wbuf = w.wbuf1.ptr()
+               wbuf = w.wbuf1
                if wbuf.nobj == 0 {
                        owbuf := wbuf
                        wbuf = trygetfull()
@@ -167,7 +152,7 @@ func (w *gcWork) tryGet() uintptr {
                                return 0
                        }
                        putempty(owbuf)
-                       w.wbuf1 = wbufptrOf(wbuf)
+                       w.wbuf1 = wbuf
                }
        }
 
@@ -180,7 +165,7 @@ func (w *gcWork) tryGet() uintptr {
 // the caller is expected to call tryGet().
 //go:nowritebarrier
 func (w *gcWork) tryGetFast() uintptr {
-       wbuf := w.wbuf1.ptr()
+       wbuf := w.wbuf1
        if wbuf == nil {
                return 0
        }
@@ -197,15 +182,15 @@ func (w *gcWork) tryGetFast() uintptr {
 // been retrieved.  get returns 0 if there are no pointers remaining.
 //go:nowritebarrier
 func (w *gcWork) get() uintptr {
-       wbuf := w.wbuf1.ptr()
+       wbuf := w.wbuf1
        if wbuf == nil {
                w.init()
-               wbuf = w.wbuf1.ptr()
+               wbuf = w.wbuf1
                // wbuf is empty at this point.
        }
        if wbuf.nobj == 0 {
                w.wbuf1, w.wbuf2 = w.wbuf2, w.wbuf1
-               wbuf = w.wbuf1.ptr()
+               wbuf = w.wbuf1
                if wbuf.nobj == 0 {
                        owbuf := wbuf
                        wbuf = getfull()
@@ -213,7 +198,7 @@ func (w *gcWork) get() uintptr {
                                return 0
                        }
                        putempty(owbuf)
-                       w.wbuf1 = wbufptrOf(wbuf)
+                       w.wbuf1 = wbuf
                }
        }
 
@@ -231,21 +216,21 @@ func (w *gcWork) get() uintptr {
 //
 //go:nowritebarrier
 func (w *gcWork) dispose() {
-       if wbuf := w.wbuf1.ptr(); wbuf != nil {
+       if wbuf := w.wbuf1; wbuf != nil {
                if wbuf.nobj == 0 {
                        putempty(wbuf)
                } else {
                        putfull(wbuf)
                }
-               w.wbuf1 = 0
+               w.wbuf1 = nil
 
-               wbuf = w.wbuf2.ptr()
+               wbuf = w.wbuf2
                if wbuf.nobj == 0 {
                        putempty(wbuf)
                } else {
                        putfull(wbuf)
                }
-               w.wbuf2 = 0
+               w.wbuf2 = nil
        }
        if w.bytesMarked != 0 {
                // dispose happens relatively infrequently. If this
@@ -265,14 +250,14 @@ func (w *gcWork) dispose() {
 // global queue.
 //go:nowritebarrier
 func (w *gcWork) balance() {
-       if w.wbuf1 == 0 {
+       if w.wbuf1 == nil {
                return
        }
-       if wbuf := w.wbuf2.ptr(); wbuf.nobj != 0 {
+       if wbuf := w.wbuf2; wbuf.nobj != 0 {
                putfull(wbuf)
-               w.wbuf2 = wbufptrOf(getempty())
-       } else if wbuf := w.wbuf1.ptr(); wbuf.nobj > 4 {
-               w.wbuf1 = wbufptrOf(handoff(wbuf))
+               w.wbuf2 = getempty()
+       } else if wbuf := w.wbuf1; wbuf.nobj > 4 {
+               w.wbuf1 = handoff(wbuf)
        } else {
                return
        }
@@ -285,7 +270,7 @@ func (w *gcWork) balance() {
 // empty returns true if w has no mark work available.
 //go:nowritebarrier
 func (w *gcWork) empty() bool {
-       return w.wbuf1 == 0 || (w.wbuf1.ptr().nobj == 0 && w.wbuf2.ptr().nobj == 0)
+       return w.wbuf1 == nil || (w.wbuf1.nobj == 0 && w.wbuf2.nobj == 0)
 }
 
 // Internally, the GC work pool is kept in arrays in work buffers.