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x86comparisonunsignedsse

SSE Compare Packed Unsigned Bytes

I'm trying to use the SSE instructions to do some image filtering. The image I'm using has a byte per pixel (255 greyscale) and I need to compare the unsigned packed bytes using a greather than comparison. I've looked into the intel's manual and the comparison exists but just for signed bytes (PCMPGTB). How could I make this comparison for the unsigned bytes? Thanks in advance

Solution

  • It's not possible to do a greather than compare in packed unsigned bytes, I've unpacked the bytes into words (as they were possitive it's like a conversion from unsigned to signed and a extension from byte to word) and compared them using PCMPGTB.