[Mono-dev] Patch for ilasm (ldc.i4 opt)

[Rodrigo Kumpera]

Patch looks good, do you have a SVN  account?


On Wed, Mar 17, 2010 at 2:22 PM, Thierry Lafage <thierry.lafage at inria.fr>wrote:

> Hi all,
>
> Here is a small patch for ilasm which makes it replace ldc.i4 with short
> forms when possible.
> Note that I'm a C# and monodevelop newbie (but I tried to respect the
> coding guidelines).
> I suggest to add the "-opt:ldc" because I would like to add the same kind
> of optimization for ldloc/stloc (use short forms when possible). For this
> latter one, the command line option could be "-opt:loc" (and we could add
> "-opt:all" to enable both at once).
> I think the impact of such a patch is quite limited, but it's important for
> us (the gcc4cli team) since we rely on ilasm to assemble the CIL code
> produced by our compiler. And these "optimizations" tasks are better suited
> to the assembler than to the compiler itself.
>
> Regards,
> Thierry Lafage.
>
>
> Index: ilasm/Driver.cs
> ===================================================================
> --- ilasm/Driver.cs     (revision 153715)
> +++ ilasm/Driver.cs     (working copy)
> @@ -20,6 +20,8 @@
>
>         public class Driver {
>
> +                               internal static bool opt_ldc = false;
> +
>                 enum Target {
>                         Dll,
>                         Exe
> @@ -270,6 +272,10 @@
>                                                else
>                                                        keyname =
> command_arg;
>                                                break;
> +                                        case "opt":
> +                                               if ("ldc" == command_arg)
> +                                                       Driver.opt_ldc =
> true;
> +                                               break;
>                                         case "scan_only":
>                                                 scan_only = true;
>                                                 break;
> @@ -344,6 +350,7 @@
>                                         "   /exe               Compile to
> executable.\n" +
>                                         "   /dll               Compile to
> library.\n" +
>                                         "   /debug             Include
> debug information.\n" +
> +                                        "   /opt:ldc           Optimize
> ldc instructions (use shorter forms when possible).\n" +
>                                        "   /key:keyfile       Strongname
> using the specified key file\n" +
>                                        "   /key:@container    Strongname
> using the specified key container\n" +
>                                         "Options can be of the form -option
> or /option\n");
> Index: ilasm/codegen/IntInstr.cs
> ===================================================================
> --- ilasm/codegen/IntInstr.cs   (revision 153715)
> +++ ilasm/codegen/IntInstr.cs   (working copy)
> @@ -27,9 +27,35 @@
>                 public override void Emit (CodeGen code_gen, MethodDef
> meth,
>                                           PEAPI.CILInstructions cil)
>                 {
> -                        cil.IntInst (op, operand);
> -                }
> +                       if (Driver.opt_ldc && op == PEAPI.IntOp.ldc_i4) {
> +                               if (operand >= -1 && operand <= 8)
> +                                       cil.Inst (getOptLdcOp (operand));
> +                               else if (operand >= -128 && operand <= 127)
> +                                       cil.IntInst (PEAPI.IntOp.ldc_i4_s,
> +                                               operand);
> +                               else
> +                                       cil.IntInst (op, operand);
> +                       } else
> +                               cil.IntInst (op, operand);
> +               }
>
> +               private PEAPI.Op getOptLdcOp (int operand)
> +               {
> +                       switch (operand) {
> +                       case -1: return PEAPI.Op.ldc_i4_m1;
> +                       case 0:  return PEAPI.Op.ldc_i4_0;
> +                       case 1:  return PEAPI.Op.ldc_i4_1;
> +                       case 2:  return PEAPI.Op.ldc_i4_2;
> +                       case 3:  return PEAPI.Op.ldc_i4_3;
> +                       case 4:  return PEAPI.Op.ldc_i4_4;
> +                       case 5:  return PEAPI.Op.ldc_i4_5;
> +                       case 6:  return PEAPI.Op.ldc_i4_6;
> +                       case 7:  return PEAPI.Op.ldc_i4_7;
> +                       case 8:  return PEAPI.Op.ldc_i4_8;
> +                       default:
> +                               throw new ArgumentOutOfRangeException
> ("operand");
> +                       }
> +               }
>         }
>
>  }
>
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