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authorMagnus Lång <[email protected]>2017-04-09 00:25:50 +0200
committerMagnus Lång <[email protected]>2017-11-05 19:03:55 +0100
commit3e881a9eb442b663c306e3fbe48488b51bc77a04 (patch)
treecf4d3d17970a6fc89c33ac563bf6f0b6e8183c50
parent7cd0a910a3d171840991092e335e9a5b2aeee74e (diff)
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hipe_rtl_lcm: Fix Lazy Code Motion bug
The lazy code motion optimisation pass could violate its guarantees eliminating partial redundancy by moving an expression to before a call instruction.
-rw-r--r--lib/hipe/rtl/hipe_rtl_lcm.erl40
1 files changed, 23 insertions, 17 deletions
diff --git a/lib/hipe/rtl/hipe_rtl_lcm.erl b/lib/hipe/rtl/hipe_rtl_lcm.erl
index 9dcdd05fb1..b0ec86eef7 100644
--- a/lib/hipe/rtl/hipe_rtl_lcm.erl
+++ b/lib/hipe/rtl/hipe_rtl_lcm.erl
@@ -226,13 +226,12 @@ insert_exprs(CFG, _, _, _, _, BetweenMap, []) ->
insert_exprs(CFG, Pred, Succ, ExprMap, IdMap, BetweenMap, [ExprId|Exprs]) ->
Expr = expr_id_map_get_expr(IdMap, ExprId),
Instr = expr_map_get_instr(ExprMap, Expr),
- case hipe_rtl_cfg:succ(CFG, Pred) of
- [_] ->
+ case try_insert_expr_last(CFG, Pred, Instr) of
+ {ok, NewCFG} ->
pp_debug(" Inserted last: ", []),
pp_debug_instr(Instr),
- NewCFG = insert_expr_last(CFG, Pred, Instr),
insert_exprs(NewCFG, Pred, Succ, ExprMap, IdMap, BetweenMap, Exprs);
- _ ->
+ not_safe ->
case hipe_rtl_cfg:pred(CFG, Succ) of
[_] ->
pp_debug(" Inserted first: ", []),
@@ -252,25 +251,31 @@ insert_exprs(CFG, Pred, Succ, ExprMap, IdMap, BetweenMap, [ExprId|Exprs]) ->
%% Recursively goes through the code in a block and returns a new block
%% with the new code inserted second to last (assuming the last expression
%% is a branch operation).
-insert_expr_last(CFG0, Label, Instr) ->
- Code0 = hipe_bb:code(hipe_rtl_cfg:bb(CFG0, Label)),
- %% FIXME: Use hipe_bb:butlast() instead?
- Code1 = insert_expr_last_work(Label, Instr, Code0),
- hipe_rtl_cfg:bb_add(CFG0, Label, hipe_bb:mk_bb(Code1)).
+try_insert_expr_last(CFG0, Label, Instr) ->
+ case hipe_rtl_cfg:succ(CFG0, Label) of
+ [_] ->
+ Code0 = hipe_bb:code(hipe_rtl_cfg:bb(CFG0, Label)),
+ case insert_expr_last_work(Instr, Code0) of
+ not_safe -> not_safe;
+ Code1 ->
+ {ok, hipe_rtl_cfg:bb_add(CFG0, Label, hipe_bb:mk_bb(Code1))}
+ end;
+ _ -> not_safe
+ end.
%%=============================================================================
%% Recursively goes through the code in a block and returns a new block
%% with the new code inserted second to last (assuming the last expression
%% is a branch operation).
-insert_expr_last_work(_, Instr, []) ->
- %% This case should not happen since this means that block was completely
- %% empty when the function was called. For compatibility we insert it last.
- [Instr];
-insert_expr_last_work(_, Instr, [Code1]) ->
+insert_expr_last_work(_Instr, [#call{}]) ->
+ %% Call instructions clobber all expressions; we musn't insert the expression
+ %% before it
+ not_safe;
+insert_expr_last_work(Instr, [Code1]) ->
%% We insert the code next to last.
[Instr, Code1];
-insert_expr_last_work(Label, Instr, [Code|Codes]) ->
- [Code|insert_expr_last_work(Label, Instr, Codes)].
+insert_expr_last_work(Instr, [Code|Codes]) ->
+ [Code|insert_expr_last_work(Instr, Codes)].
%%=============================================================================
%% Inserts expression first in the block for the given label.
@@ -305,7 +310,8 @@ insert_expr_between(CFG0, BetweenMap, Pred, Succ, Instr) ->
{value, Label} ->
pp_debug(" Using existing new bb for edge (~w,~w) with label ~w~n",
[Pred, Succ, Label]),
- {insert_expr_last(CFG0, Label, Instr), BetweenMap}
+ {ok, NewCfg} = try_insert_expr_last(CFG0, Label, Instr),
+ {NewCfg, BetweenMap}
end.
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