[clang] [CIR] Add atomic load and store operations (PR #153814)

[Bruno Cardoso Lopes via cfe-commits]

================
@@ -187,12 +244,85 @@ void AtomicInfo::emitCopyIntoMemory(RValue rvalue) const {
   }
 }
 
+static void emitAtomicOp(CIRGenFunction &cgf, AtomicExpr *expr, Address dest,
+                         Address ptr, Address val1, uint64_t size,
+                         cir::MemOrder order) {
+  std::unique_ptr<AtomicScopeModel> scopeModel = expr->getScopeModel();
+  if (scopeModel) {
+    assert(!cir::MissingFeatures::atomicScope());
+    cgf.cgm.errorNYI(expr->getSourceRange(), "emitAtomicOp: atomic scope");
+    return;
+  }
+
+  assert(!cir::MissingFeatures::atomicSyncScopeID());
+
+  CIRGenBuilderTy &builder = cgf.getBuilder();
+  mlir::Location loc = cgf.getLoc(expr->getSourceRange());
+  auto orderAttr = cir::MemOrderAttr::get(builder.getContext(), order);
+
+  switch (expr->getOp()) {
+  default:
+    cgf.cgm.errorNYI(expr->getSourceRange(), "emitAtomicOp: expr op NYI");
+    break;
+
+  case AtomicExpr::AO__c11_atomic_init:
+    llvm_unreachable("already handled!");
+
+  case AtomicExpr::AO__c11_atomic_load:
+  case AtomicExpr::AO__atomic_load: {
+    cir::LoadOp load =
+        builder.createLoad(loc, ptr, /*isVolatile=*/expr->isVolatile());
+
+    assert(!cir::MissingFeatures::atomicSyncScopeID());
+
+    load->setAttr("mem_order", orderAttr);
+
+    // TODO(cir): this logic should be part of createStore, but doing so
+    // currently breaks CodeGen/union.cpp and CodeGen/union.cpp.
+    auto ptrTy = mlir::cast<cir::PointerType>(dest.getPointer().getType());
----------------
bcardosolopes wrote:

Is this a good time to make such change to createStore? Might be cargo cult a this point.

https://github.com/llvm/llvm-project/pull/153814