Re: [gofrontend-dev] libgo patch committed: Fix 32-bit memory allocation

[Michael Hudson-Doyle <michael dot hudson at linaro dot org>]

Ian Lance Taylor <iant@google.com> writes:

> This patch to libgo fixes memory allocation on 32-bit systems when a lot
> of memory has been allocated.  The problem is described in this patch to
> the master repository: https://codereview.appspot.com/49460043 .

Here's a patch for the 4.8 branch if you are interested.  I haven't
tested it yet -- well, it's in progress but I'm not going to hang around
long enough for it to finish today.

Cheers,
mwh

diff --git a/libgo/runtime/malloc.goc b/libgo/runtime/malloc.goc
index 8ccaa6b..f0871dd 100644
--- a/libgo/runtime/malloc.goc
+++ b/libgo/runtime/malloc.goc
@@ -541,8 +541,7 @@ runtime_settype_flush(M *mp, bool sysalloc)
 
 		// (Manually inlined copy of runtime_MHeap_Lookup)
 		p = (uintptr)v>>PageShift;
-		if(sizeof(void*) == 8)
-			p -= (uintptr)runtime_mheap->arena_start >> PageShift;
+		p -= (uintptr)runtime_mheap->arena_start >> PageShift;
 		s = runtime_mheap->map[p];
 
 		if(s->sizeclass == 0) {
diff --git a/libgo/runtime/mgc0.c b/libgo/runtime/mgc0.c
index c3b3211..9f17bdc 100644
--- a/libgo/runtime/mgc0.c
+++ b/libgo/runtime/mgc0.c
@@ -239,8 +239,7 @@ markonly(void *obj)
 	// (Manually inlined copy of MHeap_LookupMaybe.)
 	k = (uintptr)obj>>PageShift;
 	x = k;
-	if(sizeof(void*) == 8)
-		x -= (uintptr)runtime_mheap->arena_start>>PageShift;
+	x -= (uintptr)runtime_mheap->arena_start>>PageShift;
 	s = runtime_mheap->map[x];
 	if(s == nil || k < s->start || k - s->start >= s->npages || s->state != MSpanInUse)
 		return false;
@@ -418,8 +417,7 @@ flushptrbuf(PtrTarget *ptrbuf, PtrTarget **ptrbufpos, Obj **_wp, Workbuf **_wbuf
 			// (Manually inlined copy of MHeap_LookupMaybe.)
 			k = (uintptr)obj>>PageShift;
 			x = k;
-			if(sizeof(void*) == 8)
-				x -= (uintptr)arena_start>>PageShift;
+			x -= (uintptr)arena_start>>PageShift;
 			s = runtime_mheap->map[x];
 			if(s == nil || k < s->start || k - s->start >= s->npages || s->state != MSpanInUse)
 				continue;
@@ -466,8 +464,7 @@ flushptrbuf(PtrTarget *ptrbuf, PtrTarget **ptrbufpos, Obj **_wp, Workbuf **_wbuf
 			// Ask span about size class.
 			// (Manually inlined copy of MHeap_Lookup.)
 			x = (uintptr)obj >> PageShift;
-			if(sizeof(void*) == 8)
-				x -= (uintptr)arena_start>>PageShift;
+			x -= (uintptr)arena_start>>PageShift;
 			s = runtime_mheap->map[x];
 
 			PREFETCH(obj);
@@ -585,8 +582,7 @@ checkptr(void *obj, uintptr objti)
 	if(t == nil)
 		return;
 	x = (uintptr)obj >> PageShift;
-	if(sizeof(void*) == 8)
-		x -= (uintptr)(runtime_mheap->arena_start)>>PageShift;
+	x -= (uintptr)(runtime_mheap->arena_start)>>PageShift;
 	s = runtime_mheap->map[x];
 	objstart = (byte*)((uintptr)s->start<<PageShift);
 	if(s->sizeclass != 0) {
diff --git a/libgo/runtime/mheap.c b/libgo/runtime/mheap.c
index b4d94b6..af46bfb 100644
--- a/libgo/runtime/mheap.c
+++ b/libgo/runtime/mheap.c
@@ -150,8 +150,7 @@ HaveSpan:
 		runtime_MSpan_Init(t, s->start + npage, s->npages - npage);
 		s->npages = npage;
 		p = t->start;
-		if(sizeof(void*) == 8)
-			p -= ((uintptr)h->arena_start>>PageShift);
+		p -= ((uintptr)h->arena_start>>PageShift);
 		if(p > 0)
 			h->map[p-1] = s;
 		h->map[p] = t;
@@ -169,8 +168,7 @@ HaveSpan:
 	s->elemsize = (sizeclass==0 ? s->npages<<PageShift : (uintptr)runtime_class_to_size[sizeclass]);
 	s->types.compression = MTypes_Empty;
 	p = s->start;
-	if(sizeof(void*) == 8)
-		p -= ((uintptr)h->arena_start>>PageShift);
+	p -= ((uintptr)h->arena_start>>PageShift);
 	for(n=0; n<npage; n++)
 		h->map[p+n] = s;
 	return s;
@@ -241,8 +239,7 @@ MHeap_Grow(MHeap *h, uintptr npage)
 	mstats.mspan_sys = h->spanalloc.sys;
 	runtime_MSpan_Init(s, (uintptr)v>>PageShift, ask>>PageShift);
 	p = s->start;
-	if(sizeof(void*) == 8)
-		p -= ((uintptr)h->arena_start>>PageShift);
+	p -= ((uintptr)h->arena_start>>PageShift);
 	h->map[p] = s;
 	h->map[p + s->npages - 1] = s;
 	s->state = MSpanInUse;
@@ -259,8 +256,7 @@ runtime_MHeap_Lookup(MHeap *h, void *v)
 	uintptr p;
 	
 	p = (uintptr)v;
-	if(sizeof(void*) == 8)
-		p -= (uintptr)h->arena_start;
+	p -= (uintptr)h->arena_start;
 	return h->map[p >> PageShift];
 }
 
@@ -281,8 +277,7 @@ runtime_MHeap_LookupMaybe(MHeap *h, void *v)
 		return nil;
 	p = (uintptr)v>>PageShift;
 	q = p;
-	if(sizeof(void*) == 8)
-		q -= (uintptr)h->arena_start >> PageShift;
+	q -= (uintptr)h->arena_start >> PageShift;
 	s = h->map[q];
 	if(s == nil || p < s->start || p - s->start >= s->npages)
 		return nil;
@@ -332,8 +327,7 @@ MHeap_FreeLocked(MHeap *h, MSpan *s)
 
 	// Coalesce with earlier, later spans.
 	p = s->start;
-	if(sizeof(void*) == 8)
-		p -= (uintptr)h->arena_start >> PageShift;
+	p -= (uintptr)h->arena_start >> PageShift;
 	if(p > 0 && (t = h->map[p-1]) != nil && t->state != MSpanInUse) {
 		tp = (uintptr*)(t->start<<PageShift);
 		*tp |= *sp;	// propagate "needs zeroing" mark