[CIR] Upstream support for calling functions via member expressions

This adds support for calling functions via class member function pointers.

Author: andykaylor

clang/lib/CIR/CodeGen/CIRGenExpr.cpp

@@ -1820,10 +1820,10 @@ CIRGenCallee CIRGenFunction::emitCallee(const clang::Expr *e) {
     // Resolve direct calls.
     const auto *funcDecl = cast<FunctionDecl>(declRef->getDecl());
     return emitDirectCallee(funcDecl);
-  } else if (isa<MemberExpr>(e)) {
-    cgm.errorNYI(e->getSourceRange(),
-                 "emitCallee: call to member function is NYI");
-    return {};
+  } else if (auto me = dyn_cast<MemberExpr>(e)) {
+    const auto *fd = cast<FunctionDecl>(me->getMemberDecl());
+    emitIgnoredExpr(me->getBase());
+    return emitDirectCallee(fd);
   } else if (auto *pde = dyn_cast<CXXPseudoDestructorExpr>(e)) {
     return CIRGenCallee::forPseudoDestructor(pde);
   }

clang/test/CIR/CodeGen/call-via-class-member-funcptr.cpp

@@ -0,0 +1,36 @@
+// RUN: %clang_cc1 -std=c++20 -triple aarch64-none-linux-android21 -fclangir -emit-cir %s -o %t.cir
+// RUN: FileCheck --input-file=%t.cir %s --check-prefix=CIR
+// RUN: %clang_cc1 -std=c++20 -triple aarch64-none-linux-android21 -fclangir -emit-llvm %s -o %t-cir.ll
+// RUN: FileCheck --input-file=%t-cir.ll %s --check-prefix=LLVM
+// RUN: %clang_cc1 -std=c++20 -triple aarch64-none-linux-android21 -emit-llvm %s -o %t.ll
+// RUN: FileCheck --input-file=%t.ll %s --check-prefix=OGCG
+
+class A {
+public:
+  static char *b(int);
+};
+
+int h=0;
+
+class F {
+public:
+  const char *b();
+  A g;
+};
+
+const char *F::b() { return g.b(h); }
+
+void fn1() { F f1; }
+
+// CIR: cir.func {{.*}} @_ZN1F1bEv
+// CIR:   %[[H_PTR:.*]] = cir.get_global @h : !cir.ptr<!s32i>
+// CIR:   %[[H_VAL:.*]] = cir.load{{.*}} %[[H_PTR]] : !cir.ptr<!s32i>, !s32i
+// CIR:   %[[RET:.*]] = cir.call @_ZN1A1bEi(%[[H_VAL]]) : (!s32i) -> !cir.ptr<!s8i>
+
+// LLVM: define {{.*}} ptr @_ZN1F1bEv
+// LLVM:   %[[VAR_H:.*]] = load i32, ptr @h
+// LLVM:   %[[RET:.*]] = call ptr @_ZN1A1bEi(i32 %[[VAR_H]])
+
+// OGCG: define {{.*}} ptr @_ZN1F1bEv
+// OGCG:   %[[VAR_H:.*]] = load i32, ptr @h
+// OGCG:   %[[RET:.*]] = call noundef ptr @_ZN1A1bEi(i32 noundef %[[VAR_H]])