[clang] [CIR] Inline trivial copy/move assignment at call sites (PR #198918)

[Erich Keane via cfe-commits]

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@@ -901,6 +901,36 @@ void CIRGenFunction::emitImplicitAssignmentOperatorBody(FunctionArgList &args) {
   assert(!cir::MissingFeatures::incrementProfileCounter());
   assert(!cir::MissingFeatures::runCleanupsScope());
 
+  // For a memcpy-equivalent assignment operator, copy the whole object, then
+  // fall through to emit the trailing `return *this`.
+  if (assignOp->isMemcpyEquivalentSpecialMember(getContext())) {
+    CanQualType recordTy =
+        getContext().getCanonicalTagType(assignOp->getParent());
+    LValue dest = makeNaturalAlignAddrLValue(loadCXXThis(), recordTy);
+    mlir::Value srcPtr = builder.createLoad(getLoc(assignOp->getLocation()),
+                                            getAddrOfLocalVar(args.back()));
+    LValue src = makeNaturalAlignAddrLValue(srcPtr, recordTy);
+    emitAggregateAssign(dest, src, recordTy);
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erichkeane wrote:

I think we should do both.  Lets leave Unions NYI here, and open a separate PR to fix the union case in the AST.  I think there is value to fixing this 'fixme', but it needs to be done with a much wider audience than this patch.



https://github.com/llvm/llvm-project/pull/198918