search for: previousvalu

I'm trying to understand how predicated/masked instructions can be generated in llvm, specifically an instruction where a set bit in the mask will write the new result into the corresponding vector lane in the destination and a clear bit will cause the lane in the destination to remain what it was before the instruction executed. I've seen a few places that suggest 'select' is the

...o >> the IR (which I don't think anyone wants to do), it's not clear to me >> how that would even work. How would you specify what value the result >> would be received for non-enabled lanes? Perhaps another parameter: >> >> %newvalue = fadd %x, %y, %mask, %previousvalue > > It depends on how you define the mask operation. > > On the Cray X1, result elements mapped to false mask values are > undefined after the operation. I assume the only point of the mask is to avoid traps/exceptions in this case (otherwise it doesn't really do anything, righ...

Jeff Bush <jeffbush001 at gmail.com> writes: > I'm trying to understand how predicated/masked instructions can be > generated in llvm, specifically an instruction where a set bit in the > mask will write the new result into the corresponding vector lane in > the destination and a clear bit will cause the lane in the destination > to remain what it was before the