[X86] Lower to SHLD/SHRD on slow machines for optsize

Use consistent rules for when to lower to SHLD/SHRD for slow machines - fixes a weird issue where funnel shift gets expanded but then X86ISelLowering's combineOr sees the optsize and combines to SHLD/SHRD, but now with the modulo amount guard......

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@349285 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed