[clang] [CIR] Upstream minimal builtin function call support (PR #142981)

[Erich Keane via cfe-commits]

================
@@ -0,0 +1,55 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This contains code to emit Builtin calls as CIR or a function call to be
+// later resolved.
+//
+//===----------------------------------------------------------------------===//
+
+#include "CIRGenCall.h"
+#include "CIRGenFunction.h"
+#include "CIRGenModule.h"
+#include "CIRGenValue.h"
+#include "mlir/IR/BuiltinAttributes.h"
+#include "mlir/IR/Value.h"
+#include "mlir/Support/LLVM.h"
+#include "clang/AST/Expr.h"
+#include "clang/AST/GlobalDecl.h"
+#include "llvm/Support/ErrorHandling.h"
+
+using namespace clang;
+using namespace clang::CIRGen;
+
+RValue CIRGenFunction::emitBuiltinExpr(const GlobalDecl &gd, unsigned builtinID,
+                                       const CallExpr *e,
+                                       ReturnValueSlot returnValue) {
+  // See if we can constant fold this builtin.  If so, don't emit it at all.
+  // TODO: Extend this handling to all builtin calls that we can constant-fold.
+  Expr::EvalResult result;
+  if (e->isPRValue() && e->EvaluateAsRValue(result, cgm.getASTContext()) &&
+      !result.hasSideEffects()) {
+    if (result.Val.isInt()) {
+      return RValue::get(builder.getConstInt(getLoc(e->getSourceRange()),
+                                             result.Val.getInt()));
+    }
+    if (result.Val.isFloat()) {
----------------
erichkeane wrote:

Do we have a test for one that has a floating point result?

https://github.com/llvm/llvm-project/pull/142981