Emit some std:: clang builtin functions (#217)

* Add support for some builtin std:: functions

clang::Builtin::BImove
clang::Builtin::BImove_if_noexcept
clang::Builtin::BIforward
clang::Builtin::BIas_const

* Add test

Author: ivanradanov

tools/mlir-clang/Lib/CGCall.cc

@@ -341,6 +341,22 @@ ValueCategory MLIRScanner::CallHelper(
   assert(0 && "no indirect");
 }
 
+std::pair<ValueCategory, bool>
+MLIRScanner::EmitClangBuiltinCallExpr(clang::CallExpr *expr) {
+  switch (expr->getBuiltinCallee()) {
+  case clang::Builtin::BImove:
+  case clang::Builtin::BImove_if_noexcept:
+  case clang::Builtin::BIforward:
+  case clang::Builtin::BIas_const: {
+    auto V = Visit(expr->getArg(0));
+    return make_pair(V, true);
+  }
+  default:
+    break;
+  }
+  return make_pair(ValueCategory(), false);
+}
+
 ValueCategory MLIRScanner::VisitCallExpr(clang::CallExpr *expr) {
 
   auto loc = getMLIRLocation(expr->getExprLoc());
@@ -368,6 +384,10 @@ ValueCategory MLIRScanner::VisitCallExpr(clang::CallExpr *expr) {
   if (valEmitted.second)
     return valEmitted.first;
 
+  valEmitted = EmitClangBuiltinCallExpr(expr);
+  if (valEmitted.second)
+    return valEmitted.first;
+
   if (auto *oc = dyn_cast<CXXOperatorCallExpr>(expr)) {
     if (oc->getOperator() == clang::OO_EqualEqual) {
       if (auto *lhs = dyn_cast<CXXTypeidExpr>(expr->getArg(0))) {

tools/mlir-clang/Lib/clang-mlir.h

@@ -290,6 +290,9 @@ class MLIRScanner : public StmtVisitor<MLIRScanner, ValueCategory> {
              ArrayRef<std::pair<ValueCategory, clang::Expr *>> arguments,
              QualType retType, bool retReference, clang::Expr *expr);
 
+  std::pair<ValueCategory, bool>
+  EmitClangBuiltinCallExpr(clang::CallExpr *expr);
+
   std::pair<ValueCategory, bool> EmitGPUCallExpr(clang::CallExpr *expr);
 
   std::pair<ValueCategory, bool> EmitBuiltinOps(clang::CallExpr *expr);

tools/mlir-clang/Test/Verification/clangbuiltin.cpp

@@ -0,0 +1,12 @@
+// RUN: mlir-clang %s --function=* -S | FileCheck %s
+
+#include <utility>
+
+float moo(float &&x) {
+  return std::move(x);
+}
+
+// CHECK:  func.func @_Z3mooOf(%arg0: memref<?xf32>)
+// CHECK-NEXT:    %0 = affine.load %arg0[0] : memref<?xf32>
+// CHECK-NEXT:    return %0 : f32
+// CHECK-NEXT:  }