This extends the early-ifcvt pass to avoid a few more cases where the resulting
select instructions would have matching operands. Additionally, we now use TII
to determine "sameness" of the operands so that as TII gets smarter, so too
will ifcvt.
The attached test case was bugpoint-reduced down from CINT2000/252.eon in the
test-suite. See: https://clang.godbolt.org/z/WvnrcrGEn
Differential Revision: https://reviews.llvm.org/D101508
Current findBestLoopTop can find and move one kind of block to top, a latch block has one successor. Another common case is:
* a latch block
* it has two successors, one is loop header, another is exit
* it has more than one predecessors
If it is below one of its predecessors P, only P can fall through to it, all other predecessors need a jump to it, and another conditional jump to loop header. If it is moved before loop header, all its predecessors jump to it, then fall through to loop header. So all its predecessors except P can reduce one taken branch.
Differential Revision: https://reviews.llvm.org/D43256
llvm-svn: 363471
The pass to expand ISEL instructions into if-then-else sequences in patch D23630
is currently disabled. This patch partially enable it by always removing the
unnecessary ISELs (all registers used by the ISELs are the same one) and folding
the ISELs which have the same input registers into unconditional copies.
Differential Revision: https://reviews.llvm.org/D40497
llvm-svn: 320414
Jon Roelofs