Slice simplification fixes.
Slice simplification fixes.

HIPERFIT/futhark,diku-dk/futhark,diku-dk/futhark,ihc/futhark,diku-dk/futhark,HIPERFIT/futhark,HIPERFIT/futhark,ihc/futhark,diku-dk/futhark,diku-dk/futhark,ihc/futhark