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ARMeilleure: A32: Implement SHSUB8 and UHSUB8 (#3089)

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* ARMeilleure: A32: Implement UHSUB8

* ARMeilleure: A32: Implement SHSUB8
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merry 2022-02-08 09:46:42 +00:00 • committed by GitHub
parent 863c581190
commit 86b37d0ff7
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45
ARMeilleure/Instructions/InstEmitAlu32.cs
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@ -392,6 +392,11 @@ namespace ARMeilleure.Instructions
EmitHadd8(context, false);
}
public static void Shsub8(ArmEmitterContext context)
{
EmitHsub8(context, false);
}
public static void Ssat(ArmEmitterContext context)
{
OpCode32Sat op = (OpCode32Sat)context.CurrOp;
@ -482,6 +487,11 @@ namespace ARMeilleure.Instructions
EmitHadd8(context, true);
}
public static void Uhsub8(ArmEmitterContext context)
{
EmitHsub8(context, true);
}
public static void Usat(ArmEmitterContext context)
{
OpCode32Sat op = (OpCode32Sat)context.CurrOp;
@ -681,6 +691,41 @@ namespace ARMeilleure.Instructions
SetIntA32(context, op.Rd, res);
}
private static void EmitHsub8(ArmEmitterContext context, bool unsigned)
{
OpCode32AluReg op = (OpCode32AluReg)context.CurrOp;
Operand m = GetIntA32(context, op.Rm);
Operand n = GetIntA32(context, op.Rn);
Operand left, right, carry, res;
// This relies on the equality x-y == (x^y) - (((x^y)&y) << 1).
// Note that x^y always contains the LSB of the result.
// Since we want to calculate (x+y)/2, we can instead calculate ((x^y)>>1) - ((x^y)&y).
carry = context.BitwiseExclusiveOr(m, n);
left = context.ShiftRightUI(carry, Const(1));
right = context.BitwiseAnd(carry, m);
// We must now perform a partitioned subtraction.
// We can do this because minuend contains 7 bit fields.
// We use the extra bit in minuend as a bit to borrow from; we set this bit.
// We invert this bit at the end as this tells us if that bit was borrowed from.
res = context.BitwiseOr(left, Const(0x80808080));
res = context.Subtract(res, right);
res = context.BitwiseExclusiveOr(res, Const(0x80808080));
if (!unsigned)
{
// We then sign extend the result into this bit.
carry = context.BitwiseAnd(carry, Const(0x80808080));
res = context.BitwiseExclusiveOr(res, carry);
}
SetIntA32(context, op.Rd, res);
}
private static void EmitSat(ArmEmitterContext context, int intMin, int intMax)
{
OpCode32Sat op = (OpCode32Sat)context.CurrOp;