[clang] [CIR] cir.call with scalar return type (PR #135552)

[Sirui Mu via cfe-commits]

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@@ -87,9 +110,48 @@ RValue CIRGenFunction::emitCall(const CIRGenFunctionInfo &funcInfo,
   assert(!cir::MissingFeatures::opCallMustTail());
   assert(!cir::MissingFeatures::opCallReturn());
 
-  // For now we just return nothing because we don't have support for return
-  // values yet.
-  RValue ret = RValue::get(nullptr);
+  RValue ret;
+  switch (retInfo.getKind()) {
+  case cir::ABIArgInfo::Direct: {
+    mlir::Type retCIRTy = convertType(retTy);
+    if (retInfo.getCoerceToType() == retCIRTy &&
+        retInfo.getDirectOffset() == 0) {
+      switch (getEvaluationKind(retTy)) {
+      case cir::TEK_Scalar: {
+        mlir::ResultRange results = theCall->getOpResults();
+        assert(results.size() == 1 && "unexpected number of returns");
+
+        // If the argument doesn't match, perform a bitcast to coerce it. This
+        // can happen due to trivial type mismatches.
+        if (results[0].getType() != retCIRTy) {
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Lancern wrote:

Removed these unnecessary braces.

https://github.com/llvm/llvm-project/pull/135552