Correctly handle method calls and function pointers for swiftasync.

Fixes rdar://75367789.

Author: varungandhi-apple

clang/lib/AST/ExprCXX.cpp

@@ -670,6 +670,7 @@ CXXMethodDecl *CXXMemberCallExpr::getMethodDecl() const {
     return cast<CXXMethodDecl>(MemExpr->getMemberDecl());
 
   // FIXME: Will eventually need to cope with member pointers.
+  // NOTE: Update makeTailCallIfSwiftAsync on fixing this.
   return nullptr;
 }
 

clang/lib/CodeGen/CGStmt.cpp

@@ -1149,10 +1149,25 @@ struct SaveRetExprRAII {
 /// codegen it as 'tail call ...; ret void;'.
 static void makeTailCallIfSwiftAsync(const CallExpr *CE, CGBuilderTy &Builder,
                                      const CGFunctionInfo *CurFnInfo) {
-  auto callee = CE->getDirectCallee();
-  if (!callee)
+  auto calleeQualType = CE->getCallee()->getType();
+  const FunctionType *calleeType = nullptr;
+  if (calleeQualType->isFunctionPointerType() ||
+      calleeQualType->isFunctionReferenceType() ||
+      calleeQualType->isBlockPointerType() ||
+      calleeQualType->isMemberFunctionPointerType()) {
+    calleeType = calleeQualType->getPointeeType()->castAs<FunctionType>();
+  } else if (auto *ty = dyn_cast<FunctionType>(calleeQualType)) {
+    calleeType = ty;
+  } else if (auto CMCE = dyn_cast<CXXMemberCallExpr>(CE)) {
+    if (auto methodDecl = CMCE->getMethodDecl()) {
+      // getMethodDecl() doesn't handle member pointers at the moment.
+      calleeType = methodDecl->getType()->castAs<FunctionType>();
+    } else {
+      return;
+    }
+  } else {
     return;
-  auto calleeType = callee->getFunctionType();
+  }
   if (calleeType->getCallConv() == CallingConv::CC_SwiftAsync
       && (CurFnInfo->getASTCallingConvention() ==
           CallingConv::CC_SwiftAsync)) {

clang/test/CodeGen/swift-async-call-conv.c

@@ -4,11 +4,11 @@
 // RUN: %clang_cc1 -triple armv7s-apple-ios9 -emit-llvm -o - %s | FileCheck %s
 // RUN: %clang_cc1 -triple armv7k-apple-ios9 -emit-llvm -o - %s | FileCheck %s
 
-// RUN: %clang_cc1 -x c++ -triple x86_64-apple-darwin10 -target-cpu core2 -emit-llvm -o - %s | FileCheck %s
-// RUN: %clang_cc1 -x c++ -triple arm64-apple-ios9 -target-cpu cyclone -emit-llvm -o - %s | FileCheck %s
-// RUN: %clang_cc1 -x c++ -triple armv7-apple-darwin9 -emit-llvm -o - %s | FileCheck %s
-// RUN: %clang_cc1 -x c++ -triple armv7s-apple-ios9 -emit-llvm -o - %s | FileCheck %s
-// RUN: %clang_cc1 -x c++ -triple armv7k-apple-ios9 -emit-llvm -o - %s | FileCheck %s
+// RUN: %clang_cc1 -x c++ -triple x86_64-apple-darwin10 -target-cpu core2 -emit-llvm -o - %s | FileCheck %s --check-prefix=CHECK --check-prefix=CPPONLY
+// RUN: %clang_cc1 -x c++ -triple arm64-apple-ios9 -target-cpu cyclone -emit-llvm -o - %s | FileCheck %s --check-prefix=CHECK --check-prefix=CPPONLY
+// RUN: %clang_cc1 -x c++ -triple armv7-apple-darwin9 -emit-llvm -o - %s | FileCheck %s --check-prefix=CHECK --check-prefix=CPPONLY
+// RUN: %clang_cc1 -x c++ -triple armv7s-apple-ios9 -emit-llvm -o - %s | FileCheck %s --check-prefix=CHECK --check-prefix=CPPONLY
+// RUN: %clang_cc1 -x c++ -triple armv7k-apple-ios9 -emit-llvm -o - %s | FileCheck %s --check-prefix=CHECK --check-prefix=CPPONLY
 
 // Test tail call behavior when a swiftasynccall function is called
 // from another swiftasynccall function.
@@ -136,3 +136,49 @@ char c_calling_async(MYBOOL b, unsigned u) {
   return x;
 }
 
+#if __cplusplus
+struct S {
+  SWIFTASYNCCALL void (*fptr)(char * ASYNC_CONTEXT);
+
+  SWIFTASYNCCALL void async_leaf_method(char * ASYNC_CONTEXT ctx) {
+    *ctx += 1;
+  }
+  SWIFTASYNCCALL void async_nonleaf_method1(char * ASYNC_CONTEXT ctx) {
+    return async_leaf_method(ctx);
+  }
+  SWIFTASYNCCALL void async_nonleaf_method2(char * ASYNC_CONTEXT ctx) {
+    return this->async_leaf_method(ctx);
+  }
+};
+
+SWIFTASYNCCALL void (S::*async_leaf_method_ptr)(char * ASYNC_CONTEXT) = &S::async_leaf_method;
+
+// CPPONLY-LABEL: swifttailcc void {{.*}}async_struct_field_and_methods
+// CPPONLY: musttail call swifttailcc void %{{[0-9]+}}
+// CPPONLY: musttail call swifttailcc void @{{.*}}async_nonleaf_method1
+// CPPONLY: musttail call swifttailcc void %{{[0-9]+}}
+// CPPONLY: musttail call swifttailcc void @{{.*}}async_nonleaf_method2
+// CPPONLY-NOT: musttail call swifttailcc void @{{.*}}async_leaf_method
+// ^ TODO: Member pointers should also work.
+SWIFTASYNCCALL void async_struct_field_and_methods(int i, S &sref, S *sptr) {
+  char x = 'a';
+  if (i == 0) {
+    return (*sref.fptr)(&x);
+  } else if (i == 1) {
+    return sref.async_nonleaf_method1(&x);
+  } else if (i == 2) {
+    return (*(sptr->fptr))(&x);
+  } else if (i == 3) {
+    return sptr->async_nonleaf_method2(&x);
+  } else if (i == 4) {
+    return (sref.*async_leaf_method_ptr)(&x);
+  }
+  return (sptr->*async_leaf_method_ptr)(&x);
+}
+
+// CPPONLY-LABEL: define{{.*}} swifttailcc void @{{.*}}async_nonleaf_method1
+// CPPONLY: musttail call swifttailcc void @{{.*}}async_leaf_method
+
+// CPPONLY-LABEL: define{{.*}} swifttailcc void @{{.*}}async_nonleaf_method2
+// CPPONLY: musttail call swifttailcc void @{{.*}}async_leaf_method
+#endif