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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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4
src/reflect/export_test.go
View file

@ -18,8 +18,6 @@ func IsRO(v Value) bool {
var CallGC = &callGC
const PtrSize = ptrSize
const BitsPointer = bitsPointer
const BitsScalar = bitsScalar
func FuncLayout(t Type, rcvr Type) (frametype Type, argSize, retOffset uintptr, stack []byte, gc []byte, ptrs bool) {
var ft *rtype
@ -38,7 +36,7 @@ func FuncLayout(t Type, rcvr Type) (frametype Type, argSize, retOffset uintptr,
}
gcdata := (*[1000]byte)(ft.gc[0])
for i := uintptr(0); i < ft.size/ptrSize; i++ {
gc = append(gc, gcdata[i/2]>>(i%2*4+2)&3)
gc = append(gc, gcdata[i/8]>>(i%8)&1)
}
ptrs = ft.kind&kindNoPointers == 0
return