[clang] [CIR] Upstream ThreeWayCmpOp (PR #169963)

[Hendrik Hübner via cfe-commits]

================
@@ -298,8 +299,63 @@ class AggExprEmitter : public StmtVisitor<AggExprEmitter> {
     Visit(e->getRHS());
   }
   void VisitBinCmp(const BinaryOperator *e) {
-    cgf.cgm.errorNYI(e->getSourceRange(), "AggExprEmitter: VisitBinCmp");
+    assert(cgf.getContext().hasSameType(e->getLHS()->getType(),
+                                        e->getRHS()->getType()));
+    const ComparisonCategoryInfo &cmpInfo =
+        cgf.getContext().CompCategories.getInfoForType(e->getType());
+    assert(cmpInfo.Record->isTriviallyCopyable() &&
+           "cannot copy non-trivially copyable aggregate");
+
+    QualType argTy = e->getLHS()->getType();
+
+    if (!argTy->isIntegralOrEnumerationType() && !argTy->isRealFloatingType() &&
+        !argTy->isNullPtrType() && !argTy->isPointerType() &&
+        !argTy->isMemberPointerType() && !argTy->isAnyComplexType())
+      llvm_unreachable("aggregate three-way comparison");
+
+    mlir::Location loc = cgf.getLoc(e->getSourceRange());
+    CIRGenBuilderTy builder = cgf.getBuilder();
+
+    if (e->getType()->isAnyComplexType())
+      llvm_unreachable("NYI");
+
+    mlir::Value lhs = cgf.emitAnyExpr(e->getLHS()).getValue();
+    mlir::Value rhs = cgf.emitAnyExpr(e->getRHS()).getValue();
+
+    mlir::Value resultScalar;
+    if (argTy->isNullPtrType()) {
+      resultScalar =
+          builder.getConstInt(loc, cmpInfo.getEqualOrEquiv()->getIntValue());
----------------
HendrikHuebner wrote:

I'm not sure how to hit this case in the first place. The clang frontend does not seem to allow three way comparisons with a null pointer constant. There is no test case in OGCG for this either.

https://github.com/llvm/llvm-project/pull/169963