gistfile1.cpp

   bool doPair(TContext &context, const TInst *uInst, const TInst *vInst, bool ignoreBankConflicts)
    {
        using namespace Pipe;
        using namespace OpType;

        const TOp& uOp = uInst->getOp();
        const TOp& vOp = vInst->getOp();

        TCorePipe uPairability = uOp.getCorePipe();
        TCorePipe vPairability = vOp.getCorePipe();

        /* We can only pair if the U-pipe's getting something that's pairable
           on U and the V-pipe's getting something that is pairable on V :) */
        if ((uPairability == eUPairable || uPairability == eUVPairable) &&
            (vPairability == eVPairable || vPairability == eUVPairable))
        {
            /* Determine which arguments access memory (if any) and how many
               vector read ports are used. */
            const TArg *uMem = NULL;
            const TArg *vMem = NULL;
            const int vecReadPorts = 3;
            
            int uPorts = countVecPortsAndGetMem(uInst, &uMem);
            int vPorts = countVecPortsAndGetMem(vInst, &vMem);
            
            /* If we exceed read port limit, can't pair! */
            if (uPorts + vPorts > vecReadPorts) return false;
            
            /* Check for bank collisions. TODO what to do with non-{0,1} probabilities? */
            if (!ignoreBankConflicts &&
                computeBankCollisionProbability(context, uInst, uMem, vInst, vMem) == 1.0f)
                return false;
            
            /* VGATHER/VSCATTER are !pairable with any other memory instructions including prefetches */
            if (uOp.getSchedOpType() == cGatherScatterOp && vMem)
                return false;
            /* VSTOREs can't pair with each other */
            if (uOp.getSchedOpType() == cVStoreOp && vOp.getSchedOpType() == cVStoreOp)
                return false;
            /* Neither inst can contain a disp and an immediate simultaneously */
            if (hasDispImmPair(uInst, uMem) || hasDispImmPair(vInst, vMem))
                return false;
            /* Two 8b instructions can't pair with each other, and any inst >8b is unpairable */
            tSizeClass uSize = getSizeClass(uInst, uMem);
            tSizeClass vSize = getSizeClass(vInst, vMem);
            if ((uSize == Size8b && vSize == Size8b) || uSize == SizeAbove8b || vSize == SizeAbove8b)
                return false;
            /* PUSH/POP are !pairable if their argument is either a [MEM] or the SR */
            if (!isPushPopPairable(uInst)) return false;
            if (!isPushPopPairable(vInst)) return false;               
            /* TEST REG,IMM is only pairable if REG = {AX, RAX}; [MEM],IMM is !pairable */
            if (!isTestPairable(uInst))    return false;
            if (!isTestPairable(vInst))    return false; 
            /* SHR/SAR/SHL/SAL are U-pairable with immediate count */
            if (!isShiftUPairable(uInst))  return false;
            /* ROR, ROL, RCR, RCL are U-pairable with an immediate count == 1 */
            if (!isRotateUPairable(uInst)) return false;

            /* TODO: JMP, CALL to a far location are NP */
        }
        else /* Well, these can't pair */
            return false;

        return true;
    }