1 files changed, 14 insertions, 13 deletions
diff --git a/lib/compiler/src/beam_type.erl b/lib/compiler/src/beam_type.erl
index 8dd6e5f1c6..26c933481a 100644
--- a/lib/compiler/src/beam_type.erl
+++ b/lib/compiler/src/beam_type.erl
@@ -329,27 +329,27 @@ build_alloc(Words, Floats) -> {alloc,[{words,Words},{floats,Floats}]}.
 
 %% flt_liveness([Instruction]) -> [Instruction]
 %%  (Re)calculate the number of live registers for each heap allocation
-%%  function. We base liveness of the number of live registers at
-%%  entry to the instruction sequence.
+%%  function. We base liveness of the number of register map at the
+%%  beginning of the instruction sequence.
 %%
 %%  A 'not_possible' term will be thrown if the set of live registers
 %%  is not continous at an allocation function (e.g. if {x,0} and {x,2}
 %%  are live, but not {x,1}).
 
-flt_liveness([{'%live',Live,_}=LiveInstr|Is]) ->
-    flt_liveness_1(Is, init_regs(Live), [LiveInstr]).
+flt_liveness([{'%live',_Live,Regs}=LiveInstr|Is]) ->
+    flt_liveness_1(Is, Regs, [LiveInstr]).
 
-flt_liveness_1([{set,Ds,Ss,{alloc,_,Alloc}}|Is], Regs0, Acc) ->
-    Live = live_regs(Regs0),
+flt_liveness_1([{set,Ds,Ss,{alloc,Live0,Alloc}}|Is], Regs0, Acc) ->
+    Live = min(Live0, live_regs(Regs0)),
     I = {set,Ds,Ss,{alloc,Live,Alloc}},
-    Regs = foldl(fun(R, A) -> set_live(R, A) end, Regs0, Ds),
+    Regs1 = init_regs(Live),
+    Regs = x_live(Ds, Regs1),
     flt_liveness_1(Is, Regs, [I|Acc]);
 flt_liveness_1([{set,Ds,_,_}=I|Is], Regs0, Acc) ->
-    Regs = foldl(fun(R, A) -> set_live(R, A) end, Regs0, Ds),
+    Regs = x_live(Ds, Regs0),
     flt_liveness_1(Is, Regs, [I|Acc]);
-flt_liveness_1([{'%live',_,_}=I|Is], Regs, Acc) ->
-    flt_liveness_1(Is, Regs, [I|Acc]);
-flt_liveness_1([], _Regs, Acc) -> reverse(Acc).
+flt_liveness_1([{'%live',_,_}], _Regs, Acc) ->
+    reverse(Acc).
 
 init_regs(Live) ->
     (1 bsl Live) - 1.
@@ -364,8 +364,9 @@ live_regs_1(R, N) ->
 	1 -> live_regs_1(R bsr 1, N+1)
     end.
 
-set_live({x,X}, Regs) -> Regs bor (1 bsl X);
-set_live(_, Regs) -> Regs.
+x_live([{x,N}|Rs], Regs) -> x_live(Rs, Regs bor (1 bsl N));
+x_live([_|Rs], Regs) -> x_live(Rs, Regs);
+x_live([], Regs) -> Regs.
 
 %% update(Instruction, TypeDb) -> NewTypeDb
 %%  Update the type database to account for executing an instruction.