From 5facb518a9ee2d756564eccd92a2c11f334d6282 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= Date: Thu, 2 Jun 2016 09:58:46 +0200 Subject: Eliminate crash for map updates in guards beam_validator would complain that x(1) is uninitialized in a test_heap instruction when attempting to compile the following code with sys_core_fold turned off: foo(M) when not (M#{true := 0}); [M] -> ok. Simplified, the generated BEAM assembly code looked like this: test is_map BadMap x(0) put_map_exact Fail x(0) => x(1) ... jump BooleanStuff BadMap: move ok => x(1) jump Fail BooleanStuff: ... move Boolean => x(2) jump Build Fail: move false => x(2) Build: test_heap 2 3 %% x(0), x(1), x(2) must be live. ... That is, if put_map_exact failed, control would transfer to the label Fail without initializing x(1). Fix that by making sure that x(1) is initilized even if put_map_exact fails: test is_map BadMap x(0) put_map_exact BadLbl x(0) => x(1) ... jump OkLbl BadLbl: move ok => x(1) jump Fail OkLbl: jump BooleanStuff BadMap: move ok => x(1) jump Fail BooleanStuff: ... move Boolean => x(2) jump Build Fail: move false => x(2) Build: test_heap 2 3 %% x(0), x(1), x(2) must be live. ... Note that this situation is rare, and that other optimization passes (beam_dead and beam_jump in particular) will clean up this mess. --- lib/compiler/src/v3_codegen.erl | 60 +++++++++++++++++++++++++++-------------- 1 file changed, 40 insertions(+), 20 deletions(-) (limited to 'lib/compiler/src/v3_codegen.erl') diff --git a/lib/compiler/src/v3_codegen.erl b/lib/compiler/src/v3_codegen.erl index f5f3c73793..4df1aadd0a 100644 --- a/lib/compiler/src/v3_codegen.erl +++ b/lib/compiler/src/v3_codegen.erl @@ -1551,12 +1551,10 @@ set_cg([{var,R}], {binary,Segs}, Le, Vdb, Bef, #cg{bfail=Bfail}=St) -> %% Now generate the complete code for constructing the binary. Code = cg_binary(PutCode, Target, Temp, Fail, MaxRegs, Le#l.a), {Sis++Code,Aft,St}; -% Map single variable key -set_cg([{var,R}], {map,Op,Map,[{map_pair,{var,_}=K,V}]}, Le, Vdb, Bef, - #cg{bfail=Bfail}=St) -> - Fail = {f,Bfail}, - {Sis,Int0} = maybe_adjust_stack(Bef, Le#l.i, Le#l.i+1, Vdb, St), +%% Map: single variable key. +set_cg([{var,R}], {map,Op,Map,[{map_pair,{var,_}=K,V}]}, Le, Vdb, Bef, St0) -> + {Sis,Int0} = maybe_adjust_stack(Bef, Le#l.i, Le#l.i+1, Vdb, St0), SrcReg = cg_reg_arg_prefer_y(Map, Int0), Line = line(Le#l.a), @@ -1570,21 +1568,16 @@ set_cg([{var,R}], {map,Op,Map,[{map_pair,{var,_}=K,V}]}, Le, Vdb, Bef, Aft = Aft0#sr{reg=put_reg(R, Aft0#sr.reg)}, Target = fetch_reg(R, Aft#sr.reg), - I = case Op of - assoc -> put_map_assoc; - exact -> put_map_exact - end, - {Sis++[Line]++[{I,Fail,SrcReg,Target,Live,{list,List}}],Aft,St}; + {Is,St1} = set_cg_map(Line, Op, SrcReg, Target, Live, List, St0), + {Sis++Is,Aft,St1}; -% Map (possibly) multiple literal keys -set_cg([{var,R}], {map,Op,Map,Es}, Le, Vdb, Bef, - #cg{bfail=Bfail}=St) -> +%% Map: (possibly) multiple literal keys. +set_cg([{var,R}], {map,Op,Map,Es}, Le, Vdb, Bef, St0) -> %% assert key literals [] = [Var||{map_pair,{var,_}=Var,_} <- Es], - Fail = {f,Bfail}, - {Sis,Int0} = maybe_adjust_stack(Bef, Le#l.i, Le#l.i+1, Vdb, St), + {Sis,Int0} = maybe_adjust_stack(Bef, Le#l.i, Le#l.i+1, Vdb, St0), SrcReg = cg_reg_arg_prefer_y(Map, Int0), Line = line(Le#l.a), @@ -1599,11 +1592,10 @@ set_cg([{var,R}], {map,Op,Map,Es}, Le, Vdb, Bef, Aft = Aft0#sr{reg=put_reg(R, Aft0#sr.reg)}, Target = fetch_reg(R, Aft#sr.reg), - I = case Op of - assoc -> put_map_assoc; - exact -> put_map_exact - end, - {Sis++[Line]++[{I,Fail,SrcReg,Target,Live,{list,List}}],Aft,St}; + {Is,St1} = set_cg_map(Line, Op, SrcReg, Target, Live, List, St0), + {Sis++Is,Aft,St1}; + +%% Everything else. set_cg([{var,R}], Con, Le, Vdb, Bef, St) -> %% Find a place for the return register first. Int = Bef#sr{reg=put_reg(R, Bef#sr.reg)}, @@ -1616,6 +1608,34 @@ set_cg([{var,R}], Con, Le, Vdb, Bef, St) -> end, {Ais,clear_dead(Int, Le#l.i, Vdb),St}. + +set_cg_map(Line, Op0, SrcReg, Target, Live, List, St0) -> + Bfail = St0#cg.bfail, + Fail = {f,St0#cg.bfail}, + Op = case Op0 of + assoc -> put_map_assoc; + exact -> put_map_exact + end, + {OkLbl,St1} = new_label(St0), + {BadLbl,St2} = new_label(St1), + Is = if + Bfail =:= 0 orelse Op =:= put_map_assoc -> + [Line,{Op,{f,0},SrcReg,Target,Live,{list,List}}]; + true -> + %% Ensure that Target is always set, even if + %% the map update operation fails. That is necessary + %% because Target may be included in a test_heap + %% instruction. + [Line, + {Op,{f,BadLbl},SrcReg,Target,Live,{list,List}}, + {jump,{f,OkLbl}}, + {label,BadLbl}, + {move,{atom,ok},Target}, + {jump,Fail}, + {label,OkLbl}] + end, + {Is,St2}. + %%% %%% Code generation for constructing binaries. %%% -- cgit v1.2.3