1 | |
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2 | (* This module provides a translation of ERTL programs to LTL |
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3 | programs. *) |
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4 | |
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5 | (* Adapted from Pottier's PP compiler *) |
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6 | |
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7 | let translate_internal f (int_fun : ERTL.internal_function) |
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8 | : LTL.internal_function = |
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9 | |
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10 | (* Allocate a reference that will hold the control flow |
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11 | graph. Define a function that generates a statement at a fresh |
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12 | label. *) |
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13 | |
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14 | let graph = ref Label.Map.empty in |
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15 | |
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16 | let fresh_label () = Label.Gen.fresh int_fun.ERTL.f_luniverse in |
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17 | |
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18 | let add_graph lbl stmt = graph := Label.Map.add lbl stmt !graph in |
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19 | |
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20 | let generate stmt = |
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21 | let l = fresh_label () in |
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22 | add_graph l stmt ; |
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23 | l in |
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24 | |
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25 | (* Build an interference graph for this function, and color |
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26 | it. Define a function that allows consulting the coloring. *) |
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27 | |
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28 | let module G = struct |
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29 | let liveafter, graph = Build.build int_fun |
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30 | let uses = Uses.examine_internal int_fun |
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31 | let verbose = false |
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32 | let () = |
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33 | if verbose then |
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34 | Printf.printf "Starting hardware register allocation for %s.\n" f |
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35 | end in |
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36 | |
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37 | let module C = Coloring.Color (G) in |
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38 | |
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39 | let lookup r = |
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40 | Interference.Vertex.Map.find (Interference.lookup G.graph r) C.coloring |
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41 | in |
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42 | |
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43 | (* Restrict the interference graph to concern spilled vertices only, |
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44 | and color it again, this time using stack slots as colors. *) |
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45 | |
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46 | let module H = struct |
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47 | let graph = Interference.droph (Interference.restrict G.graph (fun v -> |
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48 | match Interference.Vertex.Map.find v C.coloring with |
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49 | | Coloring.Spill -> |
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50 | true |
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51 | | Coloring.Color _ -> |
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52 | false |
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53 | )) |
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54 | let verbose = false |
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55 | let () = |
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56 | if verbose then |
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57 | Printf.printf "Starting stack slot allocation for %s.\n" f |
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58 | end in |
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59 | |
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60 | let module S = Spill.Color (H) in |
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61 | |
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62 | (* Define a new function that consults both colorings at once. *) |
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63 | |
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64 | let lookup r = |
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65 | match lookup r with |
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66 | | Coloring.Spill -> |
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67 | ERTLToLTLI.Spill (Interference.Vertex.Map.find (Interference.lookup H.graph r) S.coloring) |
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68 | | Coloring.Color color -> |
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69 | ERTLToLTLI.Color color |
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70 | in |
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71 | |
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72 | (* We are now ready to instantiate the functor that deals with the |
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73 | translation of instructions. The reason why we make this a |
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74 | separate functor is purely pedagogical. Smaller modules are |
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75 | easier to understand. *) |
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76 | |
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77 | (* We add the additional stack size required for spilled register to the stack |
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78 | size previously required for the function: this is the final stack size |
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79 | required for the locals. *) |
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80 | |
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81 | let locals = S.locals + int_fun.ERTL.f_stacksize in |
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82 | |
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83 | (* The full stack size is then the size of the locals in the stack plus the |
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84 | size of the formal parameters of the function. *) |
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85 | |
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86 | let stacksize = int_fun.ERTL.f_params + locals in |
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87 | |
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88 | let module I = ERTLToLTLI.Make (struct |
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89 | let lookup = lookup |
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90 | let generate = generate |
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91 | let fresh_label = fresh_label |
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92 | let add_graph = add_graph |
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93 | let locals = locals |
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94 | let stacksize = stacksize |
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95 | end) in |
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96 | |
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97 | (* Translate the instructions in the existing control flow graph. |
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98 | Pure instructions whose destination pseudo-register is dead are |
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99 | eliminated on the fly. *) |
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100 | |
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101 | let () = |
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102 | Label.Map.iter (fun label stmt -> |
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103 | let stmt = |
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104 | match Liveness.eliminable (G.liveafter label) stmt with |
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105 | | Some successor -> |
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106 | LTL.St_skip successor |
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107 | | None -> |
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108 | I.translate_statement stmt |
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109 | in |
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110 | graph := Label.Map.add label stmt !graph |
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111 | ) int_fun.ERTL.f_graph |
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112 | in |
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113 | |
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114 | (* Build a [LTL] function. *) |
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115 | |
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116 | |
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117 | |
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118 | |
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119 | let translate_funct (name, def) = |
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120 | let def' = match def with |
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121 | | ERTL.F_int def -> LTL.F_int (translate_internal name def) |
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122 | | ERTL.F_ext def -> LTL.F_ext def in |
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123 | (name, def') |
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124 | |
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125 | let translate (p : ERTL.program) : LTL.program = |
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126 | { LTL.vars = p.ERTL.vars; |
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127 | LTL.functs = List.map translate_funct p.ERTL.functs ; |
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128 | LTL.main = p.ERTL.main } |
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