The C and C++ semantics for compare_exchange require it to return a bool
indicating success. This gets mapped to LLVM IR which follows each cmpxchg with
an icmp of the value loaded against the desired value.
When lowered to ldxr/stxr loops, this extra comparison is redundant: its
results are implicit in the control-flow of the function.
This commit makes two changes: it replaces that icmp with appropriate PHI
nodes, and then makes sure earlyCSE is called after expansion to actually make
use of the opportunities revealed.
I've also added -{arm,aarch64}-enable-atomic-tidy options, so that
existing fragile tests aren't perturbed too much by the change. Many
of them either rely on undef/unreachable too pervasively to be
restored to something well-defined (particularly while making sure
they test the same obscure assert from many years ago), or depend on a
particular CFG shape, which is disrupted by SimplifyCFG.
rdar://problem/16227836
llvm-svn: 209883
Add regression tests for the following transformation:
str X, [x20]
...
add x20, x20, #32
->
str X, [x20], #32
with X being either w0, x0, s0, d0 or q0.
llvm-svn: 209715
Add regression tests for the following transformation:
ldr X, [x20]
...
add x20, x20, #32
->
ldr X, [x20], #32
with X being either w0, x0, s0, d0 or q0.
llvm-svn: 209711
Add tests for the following transform:
str X, [x0, #32]
...
add x0, x0, #32
->
str X, [x0, #32]!
with X being either w1, x1, s0, d0 or q0.
llvm-svn: 209627
We have a couple of regression tests for load/store pairing, but (to my knowledge) there are no regression tests for the load/store + add/sub folding.
As a first step towards increased test coverage of this area, this commit adds a test for one instance of a load + add to pre-indexed load transformation.
llvm-svn: 209618
