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, 16 insertions, 8 deletions

diff --git a/lib/hipe/arm/hipe_arm_ra_postconditions.erl b/lib/hipe/arm/hipe_arm_ra_postconditions.erl
index 8d1ee1cb94..23c305511f 100644
--- a/lib/hipe/arm/hipe_arm_ra_postconditions.erl
+++ b/lib/hipe/arm/hipe_arm_ra_postconditions.erl
@@ -56,6 +56,7 @@ do_insn(I, TempMap, Strategy) ->
     #pseudo_call{} -> do_pseudo_call(I, TempMap, Strategy);
     #pseudo_li{} -> do_pseudo_li(I, TempMap, Strategy);
     #pseudo_move{} -> do_pseudo_move(I, TempMap, Strategy);
+    #pseudo_spill_move{} -> do_pseudo_spill_move(I, TempMap, Strategy);
     #pseudo_switch{} -> do_pseudo_switch(I, TempMap, Strategy);
     #pseudo_tailcall{} -> do_pseudo_tailcall(I, TempMap, Strategy);
     #smull{} -> do_smull(I, TempMap, Strategy);
@@ -108,18 +109,25 @@ do_pseudo_li(I=#pseudo_li{dst=Dst}, TempMap, Strategy) ->
 
 do_pseudo_move(I=#pseudo_move{dst=Dst,src=Src}, TempMap, Strategy) ->
   %% Either Dst or Src (but not both) may be a pseudo temp.
-  %% pseudo_move and pseudo_tailcall are special cases: in
-  %% all other instructions, all temps must be non-pseudos
-  %% after register allocation.
-  case temp_is_spilled(Dst, TempMap) of
-    true -> % Src must not be a pseudo
-      {FixSrc,NewSrc,DidSpill} = fix_src1(Src, TempMap, Strategy),
-      NewI = I#pseudo_move{src=NewSrc},
-      {FixSrc ++ [NewI], DidSpill};
+  %% pseudo_move, pseudo_spill_move, and pseudo_tailcall
+  %% are special cases: in all other instructions, all
+  %% temps must be non-pseudos after register allocation.
+  case temp_is_spilled(Dst, TempMap)
+    andalso temp_is_spilled(Dst, TempMap)
+  of
+    true -> % Turn into pseudo_spill_move
+      Temp = clone(Src, temp1(Strategy)),
+      NewI = #pseudo_spill_move{dst=Dst, temp=Temp, src=Src},
+      {[NewI], true};
     _ ->
       {[I], false}
   end.
 
+do_pseudo_spill_move(I = #pseudo_spill_move{temp=Temp}, TempMap, _Strategy) ->
+  %% Temp is above the low water mark and must not have been spilled
+  false = temp_is_spilled(Temp, TempMap),
+  {[I], false}. % nothing to do
+
 do_pseudo_switch(I=#pseudo_switch{jtab=JTab,index=Index}, TempMap, Strategy) ->
   {FixJTab,NewJTab,DidSpill1} = fix_src1(JTab, TempMap, Strategy),
   {FixIndex,NewIndex,DidSpill2} = fix_src2(Index, TempMap, Strategy),