Fix Array sizeof primops to use the correct offset (which happens to be 0, so...

Fix Array sizeof primops to use the correct offset (which happens to be 0, so it worked before anyway). Makes us more future-proof, at least

compiler/codeGen/CgPrimOp.hs

@@ -212,7 +212,7 @@ emitPrimOp [r] IndexArrayOp [obj,ix]   _  = doReadPtrArrayOp r obj ix
 emitPrimOp []  WriteArrayOp [obj,ix,v] _  = doWritePtrArrayOp obj ix v
 
 emitPrimOp [res] SizeofArrayOp [arg] _
-   = stmtC $ CmmAssign (CmmLocal res) (cmmLoadIndexW arg fixedHdrSize bWord)
+   = stmtC $ CmmAssign (CmmLocal res) (cmmLoadIndexW arg (fixedHdrSize + oFFSET_StgMutArrPtrs_ptrs) bWord)
 emitPrimOp [res] SizeofMutableArrayOp [arg] live
    = emitPrimOp [res] SizeofArrayOp [arg] live
 

compiler/codeGen/StgCmmPrim.hs

@@ -288,7 +288,7 @@ emitPrimOp [r] IndexArrayOp [obj,ix]    = doReadPtrArrayOp r obj ix
 emitPrimOp []  WriteArrayOp [obj,ix,v]  = doWritePtrArrayOp obj ix v
 
 emitPrimOp [res] SizeofArrayOp [arg]
-   = emit $	mkAssign (CmmLocal res) (cmmLoadIndexW arg fixedHdrSize bWord)
+   = emit $	mkAssign (CmmLocal res) (cmmLoadIndexW arg (fixedHdrSize + oFFSET_StgMutArrPtrs_ptrs) bWord)
 emitPrimOp [res] SizeofMutableArrayOp [arg]
    = emitPrimOp [res] SizeofArrayOp [arg]