diff options
| -rw-r--r-- | lib/compiler/src/v3_codegen.erl | 41 |
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}; |