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runtime: use 1-bit pointer bitmaps in type representation

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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>
This commit is contained in:
Russ Cox 2015-04-28 00:28:47 -04:00
parent 7d9e16abc6
commit 6d8a147bef
10 changed files with 204 additions and 301 deletions
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9
src/runtime/export_test.go
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@ -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
}