LowerTypeTests: Avoid zext of ptrtoint ConstantExpr.
In the LowerTypeTests pass we used to create IR like this:
%3 = zext i8 ptrtoint (ptr @__typeid_allones7_align to i8) to i64
%4 = lshr i64 %2, %3
%5 = zext i8 sub (i8 64, i8 ptrtoint (ptr @__typeid_allones7_align to i8)) to i64
%6 = shl i64 %2, %5
%7 = or i64 %4, %6
This is because when this code was originally written there were no
funnel shifts and as I recall it was necessary to create an i8 and zext
to pointer width (instead of just having a ptrtoint of pointer width)
in order for the shl/shr/or to be pattern matched to ror. At the time
this caused no problems because there existed a zext ConstantExpr. But
after zext ConstantExpr was removed in #71040, the newly present zext
instruction can prevent pattern matching the rotate, for example if
the zext gets hoisted to a loop preheader or common ancestor of the
check. LowerTypeTests was made to use fshr in #141735 so now we can
ptrtoint to pointer width and stop creating the zext.
Reviewers: fmayer, nikic
Reviewed By: nikic
Pull Request: https://github.com/llvm/llvm-project/pull/142886
