[X86] Emit a single shuffle for the v16i8->v4i32 step of a SIGN_EXTEND_VECTOR_INREG lowering on pre-sse4.1 targets.
Previously we emitted to separate shuffles, one for unpcklbw and one for unpcklwd. Instead emit a single shuffle equivalent to both of the original shuffles. Shuffle lowering seems able to handle it. This avoids a bitcast between the two shuffles which seems helpful to DAG combine.
Remove the custom type legalization for v8i8->v8i32. I had put that in to avoid some almost duplicate punpcklbw instructions I was seeing, but this lowering change seems to fix that. It also fixes some duplicate shuffles seen in vector-sext.ll
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@347348 91177308-0d34-0410-b5e6-96231b3b80d8
6 files changed