When choosing whether a pair of loads can be combined into a single
wide load, we check that the load only has a sext user and that sext
also only has one user. But this can prevent the transformation in
the cases when parallel macs use the same loaded data multiple times.
To enable this, we need to fix up any other uses after creating the
wide load: generating a trunc and a shift + trunc pair to recreate
the narrow values. We also need to keep a record of which loads have
already been widened.
Differential Revision: https://reviews.llvm.org/D59215
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@356132 91177308-0d34-0410-b5e6-96231b3b80d8
Previously reverted in rL343082.
Original commit message:
On failing to find sequences that can be converted into dual macs,
try to find sequential 16-bit loads that are used by muls which we
can then use smultb, smulbt, smultt with a wide load.
Differential Revision: https://reviews.llvm.org/D51983
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@344693 91177308-0d34-0410-b5e6-96231b3b80d8
