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Optimize CMN/ADDS to do a single comparision like CMP/SUBS (#576)
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2 changed files with 49 additions and 9 deletions
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@ -51,6 +51,8 @@ namespace ChocolArm64.Instructions
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public static void Adds(ILEmitterCtx context)
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{
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context.TryOptMarkCondWithoutCmp();
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EmitAluLoadOpers(context);
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context.Emit(OpCodes.Add);
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@ -312,19 +312,57 @@ namespace ChocolArm64.Translation
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public void EmitCondBranch(ILLabel target, Condition cond)
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{
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if (_optOpLastCompare != null &&
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_optOpLastCompare == _optOpLastFlagSet && _branchOps.ContainsKey(cond))
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{
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if (_optOpLastCompare.Emitter == InstEmit.Subs)
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{
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Ldloc(CmpOptTmp1Index, IoType.Int, _optOpLastCompare.RegisterSize);
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Ldloc(CmpOptTmp2Index, IoType.Int, _optOpLastCompare.RegisterSize);
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Emit(_branchOps[cond], target);
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return;
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}
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else if (_optOpLastCompare.Emitter == InstEmit.Adds && cond != Condition.GeUn
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&& cond != Condition.LtUn
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&& cond != Condition.GtUn
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&& cond != Condition.LeUn)
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{
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//There are several limitations that needs to be taken into account for CMN comparisons:
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//* The unsigned comparisons are not valid, as they depend on the
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//carry flag value, and they will have different values for addition and
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//subtraction. For addition, it's carry, and for subtraction, it's borrow.
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//So, we need to make sure we're not doing a unsigned compare for the CMN case.
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//* We can only do the optimization for the immediate variants,
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//because when the second operand value is exactly INT_MIN, we can't
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//negate the value as theres no positive counterpart.
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//Such invalid values can't be encoded on the immediate encodings.
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if (_optOpLastCompare is IOpCodeAluImm64 op)
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{
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Ldloc(CmpOptTmp1Index, IoType.Int, _optOpLastCompare.RegisterSize);
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if (_optOpLastCompare.RegisterSize == RegisterSize.Int32)
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{
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EmitLdc_I4((int)-op.Imm);
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}
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else
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{
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EmitLdc_I8(-op.Imm);
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}
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Emit(_branchOps[cond], target);
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return;
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}
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}
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}
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OpCode ilOp;
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int intCond = (int)cond;
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if (_optOpLastCompare != null &&
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_optOpLastCompare == _optOpLastFlagSet && _branchOps.ContainsKey(cond))
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{
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Ldloc(CmpOptTmp1Index, IoType.Int, _optOpLastCompare.RegisterSize);
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Ldloc(CmpOptTmp2Index, IoType.Int, _optOpLastCompare.RegisterSize);
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ilOp = _branchOps[cond];
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}
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else if (intCond < 14)
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if (intCond < 14)
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{
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int condTrue = intCond >> 1;
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