[CIR] Add test for begin/end range for statements

This adds a test to verify range for loops based on begin() and end()
funtion calls. The functionality to enable this was added in previous
commits, but those commits were only indirectly related to this test.
The general intent of this commit is to work towards enabling
iterator-based range for loops.

The test did reveal one minor problem in call argument handling, which is
corrected here.

Author: andykaylor

clang/lib/CIR/CodeGen/CIRGenCall.cpp

@@ -304,7 +304,7 @@ void CIRGenFunction::emitCallArg(CallArgList &args, const clang::Expr *e,
 
   if (e->isGLValue()) {
     assert(e->getObjectKind() == OK_Ordinary);
-    args.add(emitReferenceBindingToExpr(e), argType);
+    return args.add(emitReferenceBindingToExpr(e), argType);
   }
 
   bool hasAggregateEvalKind = hasAggregateEvaluationKind(argType);

clang/test/CIR/CodeGen/forrange.cpp

@@ -0,0 +1,49 @@
+// RUN: %clang_cc1 -std=c++17 -triple x86_64-unknown-linux-gnu -fclangir -emit-cir %s -o %t.cir
+// RUN: FileCheck --input-file=%t.cir %s --check-prefix=CIR
+
+struct Element {};
+struct Container {};
+
+Element *begin(Container &);
+Element *end(Container &);
+
+void for_range() {
+  Container c;
+  for (Element &e : c)
+    ;
+}
+
+// CIR: cir.func @_Z5beginR9Container(!cir.ptr<!rec_Container>) -> !cir.ptr<!rec_Element>
+// CIR: cir.func @_Z3endR9Container(!cir.ptr<!rec_Container>) -> !cir.ptr<!rec_Element
+
+// CIR: cir.func @_Z9for_rangev()
+// CIR:    %[[C_ADDR:.*]] = cir.alloca !rec_Container{{.*}} ["c"]
+// CIR:    cir.scope {
+// CIR:      %[[RANGE_ADDR:.*]] = cir.alloca !cir.ptr<!rec_Container>{{.*}} ["__range1", init, const]
+// CIR:      %[[BEGIN_ADDR:.*]] = cir.alloca !cir.ptr<!rec_Element>{{.*}} ["__begin1", init]
+// CIR:      %[[END_ADDR:.*]] = cir.alloca !cir.ptr<!rec_Element>{{.*}} ["__end1", init]
+// CIR:      %[[E_ADDR:.*]] = cir.alloca !cir.ptr<!rec_Element>{{.*}} ["e", init, const]
+// CIR:      cir.store %[[C_ADDR]], %[[RANGE_ADDR]]
+// CIR:      %[[C_REF:.*]] = cir.load %[[RANGE_ADDR]]
+// CIR:      %[[BEGIN:.*]] = cir.call @_Z5beginR9Container(%[[C_REF]])
+// CIR:      cir.store %[[BEGIN]], %[[BEGIN_ADDR]]
+// CIR:      %[[C_REF2:.*]] = cir.load %[[RANGE_ADDR]]
+// CIR:      %[[END:.*]] = cir.call @_Z3endR9Container(%[[C_REF2]])
+// CIR:      cir.store %[[END]], %[[END_ADDR]]
+// CIR:      cir.for : cond {
+// CIR:        %[[BEGIN:.*]] = cir.load %[[BEGIN_ADDR]]
+// CIR:        %[[END:.*]] = cir.load %[[END_ADDR]]
+// CIR:        %[[CMP:.*]] = cir.cmp(ne, %[[BEGIN]], %[[END]])
+// CIR:        cir.condition(%[[CMP]])
+// CIR:      } body {
+// CIR:        %[[E:.*]] = cir.load deref %[[BEGIN_ADDR]]
+// CIR:        cir.store %[[E]], %[[E_ADDR]]
+// CIR:        cir.yield
+// CIR:      } step {
+// CIR:        %[[BEGIN:.*]] = cir.load %[[BEGIN_ADDR]]
+// CIR:        %[[STEP:.*]] = cir.const #cir.int<1>
+// CIR:        %[[NEXT:.*]] = cir.ptr_stride(%[[BEGIN]] {{.*}}, %[[STEP]] {{.*}})
+// CIR:        cir.store %[[NEXT]], %[[BEGIN_ADDR]]
+// CIR:        cir.yield
+// CIR:      }
+// CIR:    }