Revert "[ARM, Fix] Fix emitLeading/TrailingFence on old ARM processors"

It is breaking the build on the buildbots but works fine on my machine, I revert
while trying to understand what happens (it appears to depend on the compiler used
to build, I probably used a C++11 feature that is not perfectly supported by some
of the buildbots).

This reverts commit feb3176c4d006f99af8b40373abd56215a90e7cc.

llvm-svn: 217973

1 files changed, 4 insertions, 26 deletions

diff --git a/llvm/lib/Target/ARM/ARMISelLowering.cpp b/llvm/lib/Target/ARM/ARMISelLowering.cpp
index b41d1e3e97a..4195b3bf0a4 100644
--- a/llvm/lib/Target/ARM/ARMISelLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMISelLowering.cpp
@@ -10984,33 +10984,11 @@ bool ARMTargetLowering::shouldConvertConstantLoadToIntImm(const APInt &Imm,
 
 bool ARMTargetLowering::hasLoadLinkedStoreConditional() const { return true; }
 
-Instruction* ARMTargetLowering::makeDMB(IRBuilder<> &Builder,
-                                        ARM_MB::MemBOpt Domain) const {
+static void makeDMB(IRBuilder<> &Builder, ARM_MB::MemBOpt Domain) {
   Module *M = Builder.GetInsertBlock()->getParent()->getParent();
-
-  // First, if the target has no DMB, see what fallback we can use.
-  if (!Subtarget->hasDataBarrier()) {
-    // Some ARMv6 cpus can support data barriers with an mcr instruction.
-    // Thumb1 and pre-v6 ARM mode use a libcall instead and should never get
-    // here.
-    if (Subtarget->hasV6Ops() && !Subtarget->isThumb()) {
-      Function *MCR = llvm::Intrinsic::getDeclaration(M, Intrinsic::arm_mcr);
-      ArrayRef<Value*> args = {Builder.getInt32(15), Builder.getInt32(0),
-                               Builder.getInt32(0), Builder.getInt32(7),
-                               Builder.getInt32(10), Builder.getInt32(5)};
-      return Builder.CreateCall(MCR, args);
-    } else {
-      // Instead of using barriers, atomic accesses on these subtargets use
-      // libcalls.
-      llvm_unreachable("makeDMB on a target so old that it has no barriers");
-    }
-  } else {
-    Function *DMB = llvm::Intrinsic::getDeclaration(M, Intrinsic::arm_dmb);
-    // Only a full system barrier exists in the M-class architectures.
-    Domain = Subtarget->isMClass() ? ARM_MB::SY : Domain;
-    Constant *CDomain = Builder.getInt32(Domain);
-    return Builder.CreateCall(DMB, CDomain);
-  }
+  Function *DMB = llvm::Intrinsic::getDeclaration(M, Intrinsic::arm_dmb);
+  Constant *CDomain = Builder.getInt32(Domain);
+  Builder.CreateCall(DMB, CDomain);
 }
 
 // Based on http://www.cl.cam.ac.uk/~pes20/cpp/cpp0xmappings.html