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Diffstat (limited to 'ortho/mcode/ortho_code-opts.adb')
| -rw-r--r-- | ortho/mcode/ortho_code-opts.adb | 213 |
1 files changed, 213 insertions, 0 deletions
diff --git a/ortho/mcode/ortho_code-opts.adb b/ortho/mcode/ortho_code-opts.adb new file mode 100644 index 0000000..75fedd0 --- /dev/null +++ b/ortho/mcode/ortho_code-opts.adb @@ -0,0 +1,213 @@ +-- Mcode back-end for ortho - Optimization. +-- Copyright (C) 2006 Tristan Gingold +-- +-- GHDL is free software; you can redistribute it and/or modify it under +-- the terms of the GNU General Public License as published by the Free +-- Software Foundation; either version 2, or (at your option) any later +-- version. +-- +-- GHDL is distributed in the hope that it will be useful, but WITHOUT ANY +-- WARRANTY; without even the implied warranty of MERCHANTABILITY or +-- FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License +-- for more details. +-- +-- You should have received a copy of the GNU General Public License +-- along with GCC; see the file COPYING. If not, write to the Free +-- Software Foundation, 59 Temple Place - Suite 330, Boston, MA +-- 02111-1307, USA. +with Ortho_Code.Flags; + +package body Ortho_Code.Opts is + procedure Relabel_Jump (Jmp : O_Enode) + is + Label : O_Enode; + Bb : O_Enode; + begin + Label := Get_Jump_Label (Jmp); + if Get_Expr_Kind (Label) = OE_Label then + Bb := O_Enode (Get_Label_Info (Label)); + if Bb /= O_Enode_Null then + Set_Jump_Label (Jmp, Bb); + end if; + end if; + end Relabel_Jump; + + procedure Jmp_To_Bb (Subprg : Subprogram_Data_Acc) + is + First : O_Enode; + Stmt : O_Enode; + Prev : O_Enode; + Cur_Bb : O_Enode; + begin + -- Get first statement after entry. + First := Get_Stmt_Link (Subprg.E_Entry); + + -- First loop: + -- If a label belongs to a BB (ie, is at the beginning of a BB), + -- then link it to the BB. + Stmt := First; + Cur_Bb := O_Enode_Null; + loop + case Get_Expr_Kind (Stmt) is + when OE_Leave => + exit; + when OE_BB => + Cur_Bb := Stmt; + when OE_Label => + if Cur_Bb /= O_Enode_Null then + Set_Label_Info (Stmt, Int32 (Cur_Bb)); + end if; + when OE_Jump + | OE_Jump_T + | OE_Jump_F => + -- This handles backward jump. + Relabel_Jump (Stmt); + when others => + Cur_Bb := O_Enode_Null; + end case; + Stmt := Get_Stmt_Link (Stmt); + end loop; + + -- Second loop: + -- Transform jump to label to jump to BB. + Stmt := First; + Prev := O_Enode_Null; + loop + case Get_Expr_Kind (Stmt) is + when OE_Leave => + exit; + when OE_Jump + | OE_Jump_T + | OE_Jump_F => + -- This handles forward jump. + Relabel_Jump (Stmt); + -- Update PREV. + Prev := Stmt; + when OE_Label => + -- Remove the Label. + -- Do not update PREV. + if Get_Label_Info (Stmt) /= 0 then + Set_Stmt_Link (Prev, Get_Stmt_Link (Stmt)); + end if; + when others => + Prev := Stmt; + end case; + Stmt := Get_Stmt_Link (Stmt); + end loop; + end Jmp_To_Bb; + + type Oe_Kind_Bool_Array is array (OE_Kind) of Boolean; + Is_Passive_Stmt : constant Oe_Kind_Bool_Array := + (OE_Label | OE_BB | OE_End | OE_Beg => True, + others => False); + + -- Return the next statement after STMT which really execute instructions. + function Get_Fall_Stmt (Stmt : O_Enode) return O_Enode + is + Res : O_Enode; + begin + Res := Stmt; + loop + Res := Get_Stmt_Link (Res); + case Get_Expr_Kind (Res) is + when OE_Label + | OE_BB + | OE_End + | OE_Beg => + null; + when others => + return Res; + end case; + end loop; + end Get_Fall_Stmt; + + procedure Thread_Jump (Subprg : Subprogram_Data_Acc) + is + First : O_Enode; + Stmt : O_Enode; + Prev, Next : O_Enode; + Kind : OE_Kind; + begin + -- Get first statement after entry. + First := Get_Stmt_Link (Subprg.E_Entry); + + -- First loop: + -- If a label belongs to a BB (ie, is at the beginning of a BB), + -- then link it to the BB. + Stmt := First; + Prev := O_Enode_Null; + loop + Next := Get_Stmt_Link (Stmt); + Kind := Get_Expr_Kind (Stmt); + case Kind is + when OE_Leave => + exit; + when OE_Jump => + -- Remove the jump if followed by the label. + -- * For _T/_F: should convert to a ignore value. + -- Discard unreachable statements after the jump. + declare + N_Stmt : O_Enode; + P_Stmt : O_Enode; + Label : O_Enode; + Flag_Discard : Boolean; + K_Stmt : OE_Kind; + begin + N_Stmt := Next; + P_Stmt := Stmt; + Label := Get_Jump_Label (Stmt); + Flag_Discard := Kind = OE_Jump; + loop + if N_Stmt = Label then + -- Remove STMT. + Set_Stmt_Link (Prev, Next); + exit; + end if; + K_Stmt := Get_Expr_Kind (N_Stmt); + if K_Stmt = OE_Label then + -- Do not discard anymore statements, since they are + -- now reachable. + Flag_Discard := False; + end if; + if not Is_Passive_Stmt (K_Stmt) then + if not Flag_Discard then + -- We have found the next statement. + -- Keep the jump. + Prev := Stmt; + exit; + else + -- Delete insn. + N_Stmt := Get_Stmt_Link (N_Stmt); + Set_Stmt_Link (P_Stmt, N_Stmt); + end if; + else + -- Iterate. + P_Stmt := N_Stmt; + N_Stmt := Get_Stmt_Link (N_Stmt); + end if; + end loop; + end; + when others => + Prev := Stmt; + end case; + Stmt := Next; + end loop; + end Thread_Jump; + + procedure Optimize_Subprg (Subprg : Subprogram_Data_Acc) + is + begin + -- Jump optimisation: + -- * discard insns after a OE_JUMP. + -- * Remove jump if followed by label + -- (through label, BB, comments, end, line) + -- * Redirect jump to jump (infinite loop !) + -- * Revert jump_t/f if expr is not (XXX) + -- * Jmp_t/f L:; jmp L2; L1: -> jmp_f/t L2 + Thread_Jump (Subprg); + if Flags.Flag_Opt_BB then + Jmp_To_Bb (Subprg); + end if; + end Optimize_Subprg; +end Ortho_Code.Opts; + |