[dev.power64] runtime: disable GC and use a larger default stack

LGTM=rsc
R=rsc, iant
CC=golang-codereviews
https://golang.org/cl/128120043

src/pkg/runtime/malloc.go

@@ -278,7 +278,7 @@ func profilealloc(mp *m, x unsafe.Pointer, size uintptr) {
 // force = 1 - do GC regardless of current heap usage
 // force = 2 - go GC and eager sweep
 func gogc(force int32) {
-	if memstats.enablegc == 0 {
+	if GOARCH == "power64" || GOARCH == "power64le" || memstats.enablegc == 0 {
 		return
 	}
 

src/pkg/runtime/mgc0.c

@@ -1305,6 +1305,10 @@ runtime·gc(int32 force)
 	if(!mstats.enablegc || g == g->m->g0 || g->m->locks > 0 || runtime·panicking)
 		return;
 
+	if(thechar == '9') {
+		runtime·gcpercent = -1;
+		return;
+	}
 	if(runtime·gcpercent == GcpercentUnknown) {	// first time through
 		runtime·lock(&runtime·mheap);
 		if(runtime·gcpercent == GcpercentUnknown)

src/pkg/runtime/stack.h

@@ -76,7 +76,7 @@ enum {
 	// The minimum stack segment size to allocate.
 	// If the amount needed for the splitting frame + StackExtra
 	// is less than this number, the stack will have this size instead.
-	StackMin = 8192,
+	StackMin = 65536,
 	StackSystemRounded = StackSystem + (-StackSystem & (StackMin-1)),
 	FixedStack = StackMin + StackSystemRounded,