ARM & AArch64: make use of common cmpxchg idioms after expansion
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
diff --git a/llvm/test/CodeGen/ARM/2013-07-29-vector-or-combine.ll b/llvm/test/CodeGen/ARM/2013-07-29-vector-or-combine.ll
index a438c1f..05a4ef0 100644
--- a/llvm/test/CodeGen/ARM/2013-07-29-vector-or-combine.ll
+++ b/llvm/test/CodeGen/ARM/2013-07-29-vector-or-combine.ll
@@ -1,4 +1,4 @@
-; RUN: llc < %s -mcpu=cortex-a8 | FileCheck %s
+; RUN: llc < %s -mcpu=cortex-a8 -arm-atomic-cfg-tidy=0 | FileCheck %s
; ModuleID = 'bugpoint-reduced-simplified.bc'
target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:64:128-a0:0:64-n32-S64"
target triple = "armv7--linux-gnueabi"