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1143-AArch64-Eliminate-branch-before-a-stub-sec...
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File 1143-AArch64-Eliminate-branch-before-a-stub-section.patch of Package erlang
From 119b160401f8759eddad5382cc1b64a4c72ff6c3 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org> Date: Tue, 19 Sep 2023 08:46:40 +0200 Subject: [PATCH 23/25] AArch64: Eliminate branch before a stub section Because of the limited reach of branch instructions, stubs that forward branches need to be emitted at regular intervals. Each stubs section is always preceded by a `b` instruction skipping the section. Frquently, this `b` instruction is unreachable (for example, if the preceding instruction is a `ret` instruction). By keeping track of whether the current position is unreachable, unnecessary `b` instructions can be omitted. We can also emit stubs sections somewhat earlier than strictly necessary if the current position is unreachable. That will reduce the number of `b` instructions that will need to be executed. --- erts/emulator/beam/jit/arm/beam_asm.hpp | 21 +++++++++++++++++++ .../emulator/beam/jit/arm/beam_asm_global.cpp | 2 ++ .../emulator/beam/jit/arm/beam_asm_module.cpp | 16 +++++++++++--- erts/emulator/beam/jit/arm/instr_call.cpp | 8 +++++++ erts/emulator/beam/jit/arm/instr_common.cpp | 8 +++++++ erts/emulator/beam/jit/arm/instr_fun.cpp | 3 +++ erts/emulator/beam/jit/arm/instr_msg.cpp | 6 ++++++ erts/emulator/beam/jit/arm/instr_select.cpp | 3 +++ erts/emulator/beam/jit/arm/ops.tab | 6 ++++-- 9 files changed, 68 insertions(+), 5 deletions(-) diff --git a/erts/emulator/beam/jit/arm/beam_asm.hpp b/erts/emulator/beam/jit/arm/beam_asm.hpp index 9503f0bb4b..9f7f5361ae 100644 --- a/erts/emulator/beam/jit/arm/beam_asm.hpp +++ b/erts/emulator/beam/jit/arm/beam_asm.hpp @@ -835,8 +835,29 @@ class BeamModuleAssembler : public BeamAssembler, size_t last_error_offset = 0; static constexpr ptrdiff_t STUB_CHECK_INTERVAL = 4 << 10; + static constexpr ptrdiff_t STUB_CHECK_INTERVAL_UNREACHABLE = + (4 << 10) - 128; size_t last_stub_check_offset = 0; + /* Save the last known unreachable position. */ + size_t last_unreachable_offset = 0; + + /* Mark this point unreachable. Use at the end of a BEAM + * instruction. */ + void mark_unreachable() { + last_unreachable_offset = a.offset(); + } + + /* Use within BEAM instructions. */ + void mark_unreachable_check_pending_stubs() { + mark_unreachable(); + check_pending_stubs(); + } + + bool is_unreachable() { + return a.offset() == last_unreachable_offset; + } + enum Displacement : size_t { /* Pessimistic estimate for helper functions, where we don't know the * branch displacement or whether it will be used near label diff --git a/erts/emulator/beam/jit/arm/beam_asm_global.cpp b/erts/emulator/beam/jit/arm/beam_asm_global.cpp index 84cbf0a515..2e93cf9ee6 100644 --- a/erts/emulator/beam/jit/arm/beam_asm_global.cpp +++ b/erts/emulator/beam/jit/arm/beam_asm_global.cpp @@ -247,6 +247,8 @@ void BeamModuleAssembler::emit_raise_exception(const ErtsCodeMFA *exp) { fragment_call(ga->get_raise_exception_null_exp()); } + mark_unreachable(); + /* `line` instructions need to know the latest offset that may throw an * exception. See the `line` instruction for details. */ last_error_offset = a.offset(); diff --git a/erts/emulator/beam/jit/arm/beam_asm_module.cpp b/erts/emulator/beam/jit/arm/beam_asm_module.cpp index 276a560ca9..211f60dd77 100644 --- a/erts/emulator/beam/jit/arm/beam_asm_module.cpp +++ b/erts/emulator/beam/jit/arm/beam_asm_module.cpp @@ -417,6 +417,7 @@ void BeamModuleAssembler::emit_int_code_end() { * * Since the table is potentially very large, we'll emit all stubs that are * due within it so we won't have to check on every iteration. */ + mark_unreachable(); flush_pending_stubs(_dispatchTable.size() * sizeof(Uint32[8]) + dispUnknown); @@ -427,6 +428,8 @@ void BeamModuleAssembler::emit_int_code_end() { a.br(SUPER_TMP); } + mark_unreachable(); + /* Emit all remaining stubs. */ flush_pending_stubs(dispMax); } @@ -615,7 +618,10 @@ void BeamModuleAssembler::check_pending_stubs() { /* We shouldn't let too much space pass between checks. */ ASSERT((last_stub_check_offset + dispMin) >= currOffset); - if ((last_stub_check_offset + STUB_CHECK_INTERVAL) < currOffset) { + if (last_stub_check_offset + STUB_CHECK_INTERVAL < currOffset || + (is_unreachable() && + last_stub_check_offset + STUB_CHECK_INTERVAL_UNREACHABLE < + currOffset)) { last_stub_check_offset = currOffset; flush_pending_stubs(STUB_CHECK_INTERVAL * 2); @@ -638,7 +644,9 @@ void BeamModuleAssembler::flush_pending_stubs(size_t range) { next = a.newLabel(); comment("Begin stub section"); - a.b(next); + if (!is_unreachable()) { + a.b(next); + } } emit_veneer(veneer); @@ -663,7 +671,9 @@ void BeamModuleAssembler::flush_pending_stubs(size_t range) { next = a.newLabel(); comment("Begin stub section"); - a.b(next); + if (!is_unreachable()) { + a.b(next); + } } emit_constant(constant); diff --git a/erts/emulator/beam/jit/arm/instr_call.cpp b/erts/emulator/beam/jit/arm/instr_call.cpp index 8f6f587698..c7a150b6bf 100644 --- a/erts/emulator/beam/jit/arm/instr_call.cpp +++ b/erts/emulator/beam/jit/arm/instr_call.cpp @@ -50,6 +50,8 @@ void BeamModuleAssembler::emit_dispatch_return() { a.b_mi(resolve_fragment(ga->get_dispatch_return(), disp1MB)); a.ret(a64::x30); + + mark_unreachable(); } void BeamModuleAssembler::emit_return() { @@ -85,6 +87,7 @@ void BeamModuleAssembler::emit_move_call_last(const ArgYRegister &Src, a.ldp(dst.reg, a64::x30, src_ref); flush_var(dst); a.b(resolve_beam_label(CallTarget, disp128MB)); + mark_unreachable(); } else if (src_index == 0 && Support::isInt9(deallocate)) { auto dst = init_destination(Dst, TMP1); const arm::Mem src_ref = arm::Mem(E).post(deallocate); @@ -101,6 +104,7 @@ void BeamModuleAssembler::emit_move_call_last(const ArgYRegister &Src, void BeamModuleAssembler::emit_i_call_only(const ArgLabel &CallTarget) { emit_leave_erlang_frame(); a.b(resolve_beam_label(CallTarget, disp128MB)); + mark_unreachable(); } /* Handles save_calls for remote calls. When the active code index is @@ -143,6 +147,7 @@ void BeamModuleAssembler::emit_i_call_ext_only(const ArgExport &Exp) { arm::Mem target = emit_setup_dispatchable_call(ARG1); emit_leave_erlang_frame(); branch(target); + mark_unreachable(); } void BeamModuleAssembler::emit_i_call_ext_last(const ArgExport &Exp, @@ -166,6 +171,7 @@ void BeamModuleAssembler::emit_move_call_ext_last(const ArgYRegister &Src, a.ldp(dst.reg, a64::x30, src_ref); flush_var(dst); branch(target); + mark_unreachable(); } else if (src_index == 0 && Support::isInt9(deallocate)) { auto dst = init_destination(Dst, TMP1); const arm::Mem src_ref = arm::Mem(E).post(deallocate); @@ -229,6 +235,7 @@ void BeamModuleAssembler::emit_i_apply_only() { emit_leave_erlang_frame(); branch(target); + mark_unreachable(); } arm::Mem BeamModuleAssembler::emit_fixed_apply(const ArgWord &Arity, @@ -281,4 +288,5 @@ void BeamModuleAssembler::emit_apply_last(const ArgWord &Arity, emit_leave_erlang_frame(); branch(target); + mark_unreachable(); } diff --git a/erts/emulator/beam/jit/arm/instr_common.cpp b/erts/emulator/beam/jit/arm/instr_common.cpp index 808f098dac..050d7e5361 100644 --- a/erts/emulator/beam/jit/arm/instr_common.cpp +++ b/erts/emulator/beam/jit/arm/instr_common.cpp @@ -915,6 +915,7 @@ void BeamModuleAssembler::emit_is_nonempty_list(const ArgLabel &Fail, void BeamModuleAssembler::emit_jump(const ArgLabel &Fail) { a.b(resolve_beam_label(Fail, disp128MB)); + mark_unreachable(); } void BeamModuleAssembler::emit_is_atom(const ArgLabel &Fail, @@ -1066,6 +1067,7 @@ void BeamModuleAssembler::emit_is_function2(const ArgLabel &Fail, if (arity > MAX_ARG) { /* Arity is negative or too large. */ a.b(resolve_beam_label(Fail, disp128MB)); + mark_unreachable(); return; } @@ -2554,6 +2556,8 @@ void BeamModuleAssembler::emit_raise(const ArgSource &Trace, mov_var(ARG2, trace); fragment_call(ga->get_raise_shared()); + mark_unreachable(); + /* `line` instructions need to know the latest offset that may throw an * exception. See the `line` instruction for details. */ last_error_offset = a.offset(); @@ -2672,3 +2676,7 @@ void BeamModuleAssembler::emit_i_perf_counter() { a.bind(next); } + +void BeamModuleAssembler::emit_mark_unreachable() { + mark_unreachable(); +} diff --git a/erts/emulator/beam/jit/arm/instr_fun.cpp b/erts/emulator/beam/jit/arm/instr_fun.cpp index 72b00e0392..61cded38e7 100644 --- a/erts/emulator/beam/jit/arm/instr_fun.cpp +++ b/erts/emulator/beam/jit/arm/instr_fun.cpp @@ -197,6 +197,7 @@ void BeamModuleAssembler::emit_i_lambda_trampoline(const ArgLambda &Lambda, } a.b(resolve_beam_label(Lbl, disp128MB)); + mark_unreachable(); } void BeamModuleAssembler::emit_i_make_fun3(const ArgLambda &Lambda, @@ -437,12 +438,14 @@ void BeamModuleAssembler::emit_i_call_fun2_last(const ArgVal &Tag, emit_leave_erlang_frame(); a.br(target); + mark_unreachable(); } else { emit_deallocate(Deallocate); emit_leave_erlang_frame(); const auto &trampoline = lambdas[Tag.as<ArgLambda>().get()].trampoline; a.b(resolve_label(trampoline, disp128MB)); + mark_unreachable(); } } diff --git a/erts/emulator/beam/jit/arm/instr_msg.cpp b/erts/emulator/beam/jit/arm/instr_msg.cpp index b927aca686..a853d91d52 100644 --- a/erts/emulator/beam/jit/arm/instr_msg.cpp +++ b/erts/emulator/beam/jit/arm/instr_msg.cpp @@ -256,6 +256,7 @@ void BeamModuleAssembler::emit_loop_rec_end(const ArgLabel &Dest) { a.sub(FCALLS, FCALLS, imm(1)); a.b(resolve_beam_label(Dest, disp128MB)); + mark_unreachable(); } void BeamModuleAssembler::emit_wait_unlocked(const ArgLabel &Dest) { @@ -268,6 +269,7 @@ void BeamModuleAssembler::emit_wait_unlocked(const ArgLabel &Dest) { emit_leave_runtime(0); a.b(resolve_fragment(ga->get_do_schedule(), disp128MB)); + mark_unreachable(); } void BeamModuleAssembler::emit_wait_locked(const ArgLabel &Dest) { @@ -280,6 +282,10 @@ void BeamModuleAssembler::emit_wait_locked(const ArgLabel &Dest) { emit_leave_runtime(0); a.b(resolve_fragment(ga->get_do_schedule(), disp128MB)); + + /* Must check stubs here because this branch is followed by + * a label when part of `wait_timeout_locked`. */ + mark_unreachable_check_pending_stubs(); } void BeamModuleAssembler::emit_wait_timeout_unlocked(const ArgSource &Src, diff --git a/erts/emulator/beam/jit/arm/instr_select.cpp b/erts/emulator/beam/jit/arm/instr_select.cpp index b5a4bb290c..3c0c2c966c 100644 --- a/erts/emulator/beam/jit/arm/instr_select.cpp +++ b/erts/emulator/beam/jit/arm/instr_select.cpp @@ -214,6 +214,7 @@ void BeamModuleAssembler::emit_linear_search(arm::Gp comparand, /* An invalid label means fallthrough to the next instruction. */ if (fail.isValid()) { a.b(resolve_label(fail, disp128MB)); + mark_unreachable_check_pending_stubs(); } } @@ -453,6 +454,7 @@ void BeamModuleAssembler::emit_i_jump_on_val(const ArgSource &Src, embed_vararg_rodata(args, TMP2); a.ldr(TMP3, arm::Mem(TMP2, TMP1, arm::lsl(3))); a.br(TMP3); + mark_unreachable_check_pending_stubs(); if (Fail.getType() == ArgVal::Immediate) { a.bind(fail); @@ -504,6 +506,7 @@ bool BeamModuleAssembler::emit_optimized_three_way_select( /* An invalid label means fallthrough to the next instruction. */ if (fail.isValid()) { a.b(resolve_label(fail, disp128MB)); + mark_unreachable_check_pending_stubs(); } return true; diff --git a/erts/emulator/beam/jit/arm/ops.tab b/erts/emulator/beam/jit/arm/ops.tab index cd22696347..c5a7da3142 100644 --- a/erts/emulator/beam/jit/arm/ops.tab +++ b/erts/emulator/beam/jit/arm/ops.tab @@ -652,9 +652,11 @@ call_ext_only Ar=u Bif=u$is_bif | is_heavy_bif(Bif) => # return instructions. # call_ext_last u Bif u | is_exit_bif(Bif) => - call_light_bif Bif + call_light_bif Bif | mark_unreachable call_ext_only Ar=u Bif | is_exit_bif(Bif) => - allocate u Ar | call_light_bif Bif + allocate u Ar | call_light_bif Bif | mark_unreachable + +mark_unreachable # # The general case for BIFs that have no special requirements. -- 2.35.3
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