add a special case for codegen that improves the case where we have
multiple sequential cases to a) not create tons of fall-through basic blocks
and b) not recurse deeply. This fixes codegen on 100K deep cases, and improves
codegen on moderate cases from this:
switch i32 %tmp, label %sw.epilog [
i32 1000, label %sw.bb
i32 1001, label %sw.bb1
i32 1002, label %sw.bb2
i32 1003, label %sw.bb3
i32 1004, label %sw.bb4
...
sw.bb: ; preds = %entry
br label %sw.bb1
sw.bb1: ; preds = %entry, %sw.bb
br label %sw.bb2
sw.bb2: ; preds = %entry, %sw.bb1
br label %sw.bb3
sw.bb3: ; preds = %entry, %sw.bb2
br label %sw.bb4
to:
switch i32 %tmp, label %sw.epilog [
i32 1000, label %sw.bb
i32 1001, label %sw.bb
i32 1002, label %sw.bb
i32 1003, label %sw.bb
i32 1004, label %sw.bb
sw.bb: ;; many preds
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@66015 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed