[X86][SSE] Added tests showing missed truncations for sitofp conversion

SelectionDAG::ComputeNumSignBits is poor at build_vector handling, meaning that we can't see that all the vXi64 sources are in fact sign extended i32 or smaller.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297486 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed