runtime: use 1-bit pointer bitmaps in type representation

The type information in reflect.Type and the GC programs is now
1 bit per word, down from 2 bits.

The in-memory unrolled type bitmap representation are now
1 bit per word, down from 4 bits.

The conversion from the unrolled (now 1-bit) bitmap to the
heap bitmap (still 4-bit) is not optimized. A followup CL will
work on that, after the heap bitmap has been converted to 2-bit.

The typeDead optimization, in which a special value denotes
that there are no more pointers anywhere in the object, is lost
in this CL. A followup CL will bring it back in the final form of
heapBitsSetType.

Change-Id: If61e67950c16a293b0b516a6fd9a1c755b6d5549
Reviewed-on: https://go-review.googlesource.com/9702
Reviewed-by: Austin Clements <austin@google.com>

1 files changed, 1 insertions, 8 deletions

diff --git a/src/runtime/export_test.go b/src/runtime/export_test.go
index 1efe24c61a..817622abd0 100644
--- a/src/runtime/export_test.go
+++ b/src/runtime/export_test.go
@@ -76,15 +76,8 @@ func ParForIters(desc *ParFor, tid uint32) (uint32, uint32) {
 }
 
 func GCMask(x interface{}) (ret []byte) {
-	e := (*eface)(unsafe.Pointer(&x))
-	s := (*slice)(unsafe.Pointer(&ret))
 	systemstack(func() {
-		var len uintptr
-		var a *byte
-		getgcmask(e.data, e._type, &a, &len)
-		s.array = unsafe.Pointer(a)
-		s.len = int(len)
-		s.cap = s.len
+		ret = getgcmask(x)
 	})
 	return
 }