[clang] [llvm] [PAC][Driver] Implement `-mbranch-protection=pauthabi` option (PR #97237)

[Daniil Kovalev via cfe-commits]

================
@@ -1484,6 +1484,39 @@ void AddUnalignedAccessWarning(ArgStringList &CmdArgs) {
 }
 }
 
+static void handlePAuthABIOption(const ArgList &DriverArgs,
+                                 ArgStringList &CC1Args, const Driver &D) {
+  if (!DriverArgs.hasArg(options::OPT_fptrauth_intrinsics,
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kovdan01 wrote:

> See addOptInFlag.

Do you mean that we need to replace

```
  if (!DriverArgs.hasArg(options::OPT_fptrauth_xxx,
                         options::OPT_fno_ptrauth_xxx))
    CC1Args.push_back("-fptrauth-xxx");
```

with

```
  DriverArgs.addOptInFlag(CC1Args, options::OPT_fptrauth_xxx,
                          options::OPT_fno_ptrauth_xxx);
```

...?

If so, this does not look correct - `addOptInFlag` would add the flag present (if any) in `DriverArgs` to `CC1Args`, but we want to append a list of ptrauth flags to cc1 args unconditionally if `pauthabi` is passed as branch protection.

Do I miss smth? I suppose I might have misunderstood you point.

> But the implementation seems quite different from the title/description.

Hmm, it actually looks consistent to me, the implementation seems matching the description from my point of view - we want to add a bunch of arguments with `-mbranch-protection=pauthabi` used as a shortcut, we do that. Could you please describe what is inconsistent between description and implementation in a bit more detail?

https://github.com/llvm/llvm-project/pull/97237