diff options
Diffstat (limited to 'asmcomp/liveness.ml')
| -rw-r--r-- | asmcomp/liveness.ml | 45 |
1 files changed, 26 insertions, 19 deletions
diff --git a/asmcomp/liveness.ml b/asmcomp/liveness.ml index 434d506558..7e3f1fe080 100644 --- a/asmcomp/liveness.ml +++ b/asmcomp/liveness.ml @@ -16,13 +16,13 @@ open Mach let live_at_exit = ref [] + let find_live_at_exit k = try List.assoc k !live_at_exit with - | Not_found -> Misc.fatal_error "Spill.find_live_at_exit" + | Not_found -> Misc.fatal_error "Liveness.find_live_at_exit" -let live_at_break = ref Reg.Set.empty let live_at_raise = ref Reg.Set.empty let rec live i finally = @@ -37,8 +37,30 @@ let rec live i finally = i.live <- finally; finally | Ireturn | Iop(Itailcall_ind) | Iop(Itailcall_imm _) -> - (* i.live remains empty since no regs are live across *) + i.live <- Reg.Set.empty; (* no regs are live across *) Reg.set_of_array i.arg + | Iop op -> + let after = live i.next finally in + if Proc.op_is_pure op && Reg.disjoint_set_array after i.res then begin + (* This operation is dead code. Ignore its arguments. *) + i.live <- after; + after + end else begin + let across_after = Reg.diff_set_array after i.res in + let across = + match op with + | Icall_ind | Icall_imm _ | Iextcall _ + | Iintop Icheckbound | Iintop_imm(Icheckbound, _) -> + (* The function call may raise an exception, branching to the + nearest enclosing try ... with. Similarly for bounds checks. + Hence, everything that must be live at the beginning of + the exception handler must also be live across this instr. *) + Reg.Set.union across_after !live_at_raise + | _ -> + across_after in + i.live <- across; + Reg.add_set_array across i.arg + end | Iifthenelse(test, ifso, ifnot) -> let at_join = live i.next finally in let at_fork = Reg.Set.union (live ifso at_join) (live ifnot at_join) in @@ -90,23 +112,8 @@ let rec live i finally = i.live <- before_body; before_body | Iraise _ -> - (* i.live remains empty since no regs are live across *) + i.live <- !live_at_raise; Reg.add_set_array !live_at_raise i.arg - | _ -> - let across_after = Reg.diff_set_array (live i.next finally) i.res in - let across = - match i.desc with - Iop Icall_ind | Iop(Icall_imm _) | Iop(Iextcall _) - | Iop(Iintop Icheckbound) | Iop(Iintop_imm(Icheckbound, _)) -> - (* The function call may raise an exception, branching to the - nearest enclosing try ... with. Similarly for bounds checks. - Hence, everything that must be live at the beginning of - the exception handler must also be live across this instr. *) - Reg.Set.union across_after !live_at_raise - | _ -> - across_after in - i.live <- across; - Reg.add_set_array across i.arg let fundecl ppf f = let initially_live = live f.fun_body Reg.Set.empty in |