hipe: Add pseudo_spill_f?move instructions

These pseudo instructions are added to all backends and allow spill slot
to spill slot move coalescing in a clean way.

They have regular move semantics, but contain an additional scratch
register to be used if both source and destination are spilled, and can
not be move coalesced.

Additionally, a register allocator callback
Target:is_spill_move(Instr, Context) is added which allows the spill
slot allocators to check for these instructions and try to coalesce the
spill slots the two temporaries are allocated to.

1 files changed, 22 insertions, 0 deletions

diff --git a/lib/hipe/arm/hipe_arm_frame.erl b/lib/hipe/arm/hipe_arm_frame.erl
index e323907e31..a1004fb609 100644
--- a/lib/hipe/arm/hipe_arm_frame.erl
+++ b/lib/hipe/arm/hipe_arm_frame.erl
@@ -69,6 +69,8 @@ do_insn(I, LiveOut, Context, FPoff) ->
       do_pseudo_call_prepare(I, FPoff);
     #pseudo_move{} ->
       {do_pseudo_move(I, Context, FPoff), FPoff};
+    #pseudo_spill_move{} ->
+      {do_pseudo_spill_move(I, Context, FPoff), FPoff};
     #pseudo_tailcall{} ->
       {do_pseudo_tailcall(I, Context), context_framesize(Context)};
     _ ->
@@ -100,6 +102,26 @@ pseudo_offset(Temp, FPoff, Context) ->
   FPoff + context_offset(Context, Temp).
 
 %%%
+%%% Moves from one spill slot to another
+%%%
+
+do_pseudo_spill_move(I, Context, FPoff) ->
+  #pseudo_spill_move{dst=Dst, temp=Temp, src=Src} = I,
+  case temp_is_pseudo(Src) andalso temp_is_pseudo(Dst) of
+    false -> % Register allocator changed its mind, turn back to move
+      do_pseudo_move(hipe_arm:mk_pseudo_move(Dst, Src), Context, FPoff);
+    true ->
+      SrcOffset = pseudo_offset(Src, FPoff, Context),
+      DstOffset = pseudo_offset(Dst, FPoff, Context),
+      case SrcOffset =:= DstOffset of
+	true -> []; % omit move-to-self
+	false ->
+	  mk_load('ldr', Temp, SrcOffset, mk_sp(),
+		  mk_store('str', Temp, DstOffset, mk_sp(), []))
+      end
+  end.
+
+%%%
 %%% Return - deallocate frame and emit 'ret $N' insn.
 %%%