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-rw-r--r--lib/compiler/src/v3_codegen.erl41
1 files changed, 36 insertions, 5 deletions
diff --git a/lib/compiler/src/v3_codegen.erl b/lib/compiler/src/v3_codegen.erl
index 4c2a1c6dea..2138321a39 100644
--- a/lib/compiler/src/v3_codegen.erl
+++ b/lib/compiler/src/v3_codegen.erl
@@ -743,11 +743,42 @@ block_cg(Es, Le, _Vdb, Bef, St) ->
block_cg(Es, Le, Bef, #cg{is_top_block=false}=St) ->
cg_block(Es, Le#l.vdb, Bef, St);
-block_cg(Es, Le, Bef, St0) ->
- {Is0,Aft,St} = cg_block(Es, Le#l.vdb, Bef,
- St0#cg{is_top_block=false,need_frame=false}),
- Is = top_level_block(Is0, Aft, max_reg(Bef#sr.reg), St),
- {Is,Aft,St#cg{is_top_block=true}}.
+block_cg(Es, Le, Bef, #cg{is_top_block=true}=St0) ->
+ %% No stack frame has been established yet. Do we need one?
+ case need_stackframe(Es) of
+ true ->
+ %% We need a stack frame. Generate the code and add the
+ %% code for creating and deallocating the stack frame.
+ {Is0,Aft,St} = cg_block(Es, Le#l.vdb, Bef,
+ St0#cg{is_top_block=false,need_frame=false}),
+ Is = top_level_block(Is0, Aft, max_reg(Bef#sr.reg), St),
+ {Is,Aft,St#cg{is_top_block=true}};
+ false ->
+ %% This sequence of instructions ending in a #k_match{} (a
+ %% 'case' or 'if') in the Erlang code does not need a
+ %% stack frame yet. Delay the creation (if a stack frame
+ %% is needed at all, it will be created inside the
+ %% #k_match{}).
+ cg_list(Es, Le#l.vdb, Bef, St0)
+ end.
+
+%% need_stackframe([Kexpr]) -> true|false.
+%% Does this list of instructions need a stack frame?
+%%
+%% A sequence of instructions that don't clobber the X registers
+%% followed by a single #k_match{} doesn't need a stack frame.
+
+need_stackframe([H|T]) ->
+ case H of
+ #k_bif{op=#k_internal{}} -> true;
+ #k_put{arg=#k_binary{}} -> true;
+ #k_bif{} -> need_stackframe(T);
+ #k_put{} -> need_stackframe(T);
+ #k_guard_match{} -> need_stackframe(T);
+ #k_match{} when T =:= [] -> false;
+ _ -> true
+ end;
+need_stackframe([]) -> false.
cg_block([], _Vdb, Bef, St0) ->
{[],Bef,St0};