[clang] ObjcRuntime.h: Add mips64, aarch64, and riscv64 to non-legacy dispatch (PR #76694)

[Hugo Melder via cfe-commits]

hmelder wrote:

It seems like isLegacyDispatchDefaultForArch is only called by the driver, and not when passing `-cc1`.

https://github.com/llvm/llvm-project/blob/11ac97c67a9315dce48fd938d68ae991e3559f10/clang/lib/Driver/ToolChains/Clang.cpp#L3935-L3953

Using the driver instead of the frontend does not work as there are platform checks in `Clang::AddObjCRuntimeArgs`.

Example on macOS:
```sh
clang: error: GNUstep Objective-C runtime version 2 incompatible with target binary format
```

The result is that without specifying `-fobjc-dispatch-method=mixed` or `-fobjc-dispatch-method=no-legacy`, the frontend will always emit `call ptr @objc_msg_lookup_sender`.

Do you have an idea on how we can test this instead?

Tested with

```sh
#flags="-fobjc-dispatch-method=mixed"
flags=""
rt=gnustep-2.0
triple="x86_64-unknown-freebsd"

build-llvm/bin/clang -cc1\
		-triple ${triple} \
		-fobjc-runtime=${rt} ${flags} \
		-emit-llvm -o - gnustep2-message-dispatch.m | less
```

<details>
<summary>gnustep2-message-dispatch.m</summary>

```objc
// DEFINE: %{triple} =
// DEFINE: %{ver} =
// DEFINE: %{prefix} = CHECK-MSG-SEND
// DEFINE: %{check} = %clang_cc1 -triple %{triple} -fobjc-runtime=gnustep-%{ver} -emit-llvm -o - %s | FileCheck %s -check-prefix %{prefix}


// REDEFINE: %{ver} = 1.6
// REDEFINE: %{triple} = x86_64-unknown-freebsd
// RUN: %{check}
// REDEFINE: %{triple} = arm-unknown-freebsd
// RUN: %{check}
// REDEFINE: %{prefix} = CHECK-MSG-LOOKUP
// REDEFINE: %{triple} = aarch64-unknown-freebsd
// RUN: %{check}
// REDEFINE: %{triple} = mips64-unknown-freebsd
// RUN: %{check}
// REDEFINE: %{triple} = riscv64-unknown-freebsd
// RUN: %{check}

// REDEFINE: %{ver} = 1.9
// REDEFINE: %{prefix} = CHECK-MSG-SEND
// REDEFINE: %{triple} = x86_64-unknown-freebsd
// RUN: %{check}
// REDEFINE: %{triple} = arm-unknown-freebsd
// RUN: %{check}
// REDEFINE: %{triple} = aarch64-unknown-freebsd
// RUN: %{check}
// REDEFINE: %{triple} = mips64-unknown-freebsd
// RUN: %{check}
// REDEFINE: %{prefix} = CHECK-MSG-LOOKUP
// REDEFINE: %{triple} = riscv64-unknown-freebsd
// RUN: %{check}

// REDEFINE: %{ver} = 2.2
// REDEFINE: %{prefix} = CHECK-MSG-SEND
// REDEFINE: %{triple} = x86_64-unknown-freebsd
// RUN: %{check}
// REDEFINE: %{triple} = arm-unknown-freebsd
// RUN: %{check}
// REDEFINE: %{triple} = aarch64-unknown-freebsd
// RUN: %{check}
// REDEFINE: %{triple} = mips64-unknown-freebsd
// RUN: %{check}
// REDEFINE: %{triple} = riscv64-unknown-freebsd
// RUN: %{check}

typedef struct {
  int x;
  int y;
  int z[10];
} MyPoint;

void f0(id a) {
  int i;
  MyPoint pt = { 1, 2};

  // CHECK-MSG-SEND: call {{.*}} @objc_msgSend
  // CHECK-MSG-LOOKUP: call {{.*}} @objc_msg_lookup(
  [a print0];

  // CHECK-MSG-SEND: call {{.*}} @objc_msgSend
  // CHECK-MSG-LOOKUP: call {{.*}} @objc_msg_lookup(
  [a print1: 10];

  // CHECK-MSG-SEND: call {{.*}} @objc_msgSend
  // CHECK-MSG-LOOKUP: call {{.*}} @objc_msg_lookup(
  [a print2: 10 and: "hello" and: 2.2];

  // CHECK-MSG-SEND: call {{.*}} @objc_msgSend
  // CHECK-MSG-LOOKUP: call {{.*}} @objc_msg_lookup(
  [a takeStruct: pt ];
}
```

</details>

https://github.com/llvm/llvm-project/pull/76694