[Power] Use AtomicExpandPass for fence insertion, and use lwsync where appropriate
Summary:
This patch makes use of AtomicExpandPass in Power for inserting fences around
atomic as part of an effort to remove fence insertion from SelectionDAGBuilder.
As a big bonus, it lets us use sync 1 (lightweight sync, often used by the mnemonic
lwsync) instead of sync 0 (heavyweight sync) in many cases.
I also added a test, as there was no test for the barriers emitted by the Power
backend for atomic loads and stores.
Test Plan: new test + make check-all
Reviewers: jfb
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D5180
llvm-svn: 218331
diff --git a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
index d96cdab..e216a72c 100644
--- a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -6538,6 +6538,38 @@
// Other Lowering Code
//===----------------------------------------------------------------------===//
+static Instruction* callIntrinsic(IRBuilder<> &Builder, Intrinsic::ID Id) {
+ Module *M = Builder.GetInsertBlock()->getParent()->getParent();
+ Function *Func = Intrinsic::getDeclaration(M, Id);
+ return Builder.CreateCall(Func);
+}
+
+// The mappings for emitLeading/TrailingFence is taken from
+// http://www.cl.cam.ac.uk/~pes20/cpp/cpp0xmappings.html
+Instruction* PPCTargetLowering::emitLeadingFence(IRBuilder<> &Builder,
+ AtomicOrdering Ord, bool IsStore,
+ bool IsLoad) const {
+ if (Ord == SequentiallyConsistent)
+ return callIntrinsic(Builder, Intrinsic::ppc_sync);
+ else if (isAtLeastRelease(Ord))
+ return callIntrinsic(Builder, Intrinsic::ppc_lwsync);
+ else
+ return nullptr;
+}
+
+Instruction* PPCTargetLowering::emitTrailingFence(IRBuilder<> &Builder,
+ AtomicOrdering Ord, bool IsStore,
+ bool IsLoad) const {
+ if (IsLoad && isAtLeastAcquire(Ord))
+ return callIntrinsic(Builder, Intrinsic::ppc_lwsync);
+ // FIXME: this is too conservative, a dependent branch + isync is enough.
+ // See http://www.cl.cam.ac.uk/~pes20/cpp/cpp0xmappings.html and
+ // http://www.rdrop.com/users/paulmck/scalability/paper/N2745r.2011.03.04a.html
+ // and http://www.cl.cam.ac.uk/~pes20/cppppc/ for justification.
+ else
+ return nullptr;
+}
+
MachineBasicBlock *
PPCTargetLowering::EmitAtomicBinary(MachineInstr *MI, MachineBasicBlock *BB,
bool is64bit, unsigned BinOpcode) const {