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How to "optimize" self-defined 32bit shift-left routine ?

Jimmy liao

Dear all,
I encountered one problem about "executing self-defined 32bit shift-left routine too long"...

That is, I built my own routine to execute 32-bit shift left operation and found it takes too long(Due to some reason 32bit shift left is NOT allowed in my project currently...)

[code body]

UINT32 ShiftLeft32Bits(UINT32 Operand, UINT8 ShiftValue){
        bit     Carry;
        OperandDW = Operand;
        while(ShiftValue>0){
                Carry=0;
                if(OperandDWLo&0x8000)
                        Carry=1;
                OperandDWLo<<=1;
                OperandDWHi = (OperandDWHi<<1) | Carry;
                ShiftValue-=1;
        }
        return OperandDW;
}

[Statistics]
if "Operand = ShiftLeft32Bits(x1, 31);"
=> cost 60us ( where Operand,x1 are 4-byte xdata variables)

My question is: is it possible to "optimize" above code segments(favor speed) ? Thanks in advance...

p.s I am implementing sha256 calculation...

Parents
  • 0 in reply to HansBernhard Broeker

    You've basically built yourself a solid wall and now you keep running head-first into it instead of considering that it might hurt less if there was a hole to pass through. Might want to call it "door".

    I assume the the OP is running into the old problem of having responsibility without authority, i.e. it's his job to fix the problem, but he doesn't have the authority to implement the effective, straightforward solution.

Reply
  • 0 in reply to HansBernhard Broeker

    You've basically built yourself a solid wall and now you keep running head-first into it instead of considering that it might hurt less if there was a hole to pass through. Might want to call it "door".

    I assume the the OP is running into the old problem of having responsibility without authority, i.e. it's his job to fix the problem, but he doesn't have the authority to implement the effective, straightforward solution.

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