[clang][cli] Do not marshall only CC1Option flags in BoolOption

We cannot be sure whether a flag is CC1Option inside the definition of `BoolOption`. Take the example below:

```
let Flags = [CC1Option] in {
  defm xxx : BoolOption<...>;
}
```

where TableGen applies `Flags = [CC1Option]` to the `xxx` and `no_xxx` records **after** they have been is fully declared by `BoolOption`.

For the refactored `-f[no-]debug-pass-manager` flags (see the diff), this means `BoolOption` never adds any marshalling info, as it doesn't see either of the flags as `CC1Option`.

For that reason, we should defensively append the marshalling information to both flags inside `BoolOption`. Now the check for `CC1Option` needs to happen later, in the parsing macro, when all TableGen logic has been resolved.

However, for some flags defined through `BoolOption`, we can run into issues:

```
// Options.td
def fenable_xxx : /* ... */;

// Both flags are CC1Option, the first is implied.
defm xxx : BoolOption<"xxx,
  "Opts.Xxx", DefaultsToFalse,
  ChangedBy<PosFlag, [CC1Option], "", [fenable_xxx]>,
  ResetBy<NegFlag, [CC1Option]>>;
```

When parsing `clang -cc1 -fenable-xxx`:
* we run parsing for `PosFlag`:
  * set `Opts.Xxx` to default `false`,
  * discover `PosFlag` is implied by `-fenable-xxx`: set `Opts.Xxx` to `true`,
  * don't see `-fxxx` on command line: do nothing,
* we run parsing for `NegFlag`:
  * set `Opts.Xxx` to default `false`,
  * discover `NegFlag` cannot be implied: do nothing,
  * don't see `-fno-xxx` on command line: do nothing.

Now we ended up with `Opts.Xxx` set to `false` instead of `true`. For this reason, we need to ensure to append the same `ImpliedByAnyOf` instance to both flags.

This means both parsing runs now behave identically (they set the same default value, run the same "implied by" check, and call `makeBooleanOptionNormalizer` that already has information on both flags, so it returns the same value in both calls).

The solution works well, but what might be confusing is this: you have defined a flag **A** that is not `CC1Option`, but can be implied by another flag **B** that is `CC1Option`:
* if **A** is defined manually, it will never get implied, as the code never runs
```
def no_signed_zeros : Flag<["-"], "fno-signed-zeros">, Group<f_Group>, Flags<[]>,
  MarshallingInfoFlag<"LangOpts->NoSignedZero">, ImpliedByAnyOf<[menable_unsafe_fp_math]>;
```
* if **A** is defined by `BoolOption`, it could get implied, as the code is run by its `CC1Option` counterpart:
```
defm signed_zeros : BoolOption<"signed-zeros",
  "LangOpts->NoSignedZero", DefaultsToFalse,
  ChangedBy<NegFlag, [], "Allow optimizations that ignore the sign of floating point zeros",
            [cl_no_signed_zeros, menable_unsafe_fp_math]>,
  ResetBy<PosFlag, [CC1Option]>, "f">, Group<f_Group>;
```

This is a surprising inconsistency.

One solution might be to somehow propagate the final `Flags` of the implied flag in `ImpliedByAnyOf` and check whether it has `CC1Option` in the parsing macro. However, I think it doesn't make sense to spend time thinking about a corner case that won't come up in real code.

An observation: it is unfortunate that the marshalling information is a part of the flag definition. If we represented it in a separate structure, we could avoid the "double parsing" problem by having a single source of truth. This would require a lot of additional work though.

Note: the original patch missed the `CC1Option` check in the parsing macro, making my reasoning here incomplete. Moreover, it contained a change to denormalization that wasn't necessarily related to these changes, so I've extracted that to a follow-up patch: D93094.

Reviewed By: dexonsmith, Bigcheese

Differential Revision: https://reviews.llvm.org/D93008

1 files changed, 49 insertions, 0 deletions

diff --git a/clang/unittests/Frontend/CompilerInvocationTest.cpp b/clang/unittests/Frontend/CompilerInvocationTest.cpp
index 41da5af..156e3393 100644
--- a/clang/unittests/Frontend/CompilerInvocationTest.cpp
+++ b/clang/unittests/Frontend/CompilerInvocationTest.cpp
@@ -238,6 +238,55 @@ TEST_F(CommandLineTest, BoolOptionDefaultArbitraryTwoFlagsPresentReset) {
   ASSERT_THAT(GeneratedArgs, Not(Contains(StrEq(PassManagerChangedByFlag))));
 }
 
+// Boolean option that gets the CC1Option flag from a let statement (which
+// is applied **after** the record is defined):
+//
+//   let Flags = [CC1Option] in {
+//     defm option : BoolOption<...>;
+//   }
+
+TEST_F(CommandLineTest, BoolOptionCC1ViaLetPresentNone) {
+  const char *Args[] = {""};
+
+  CompilerInvocation::CreateFromArgs(Invocation, Args, *Diags);
+
+  ASSERT_FALSE(Diags->hasErrorOccurred());
+  ASSERT_FALSE(Invocation.getCodeGenOpts().DebugPassManager);
+
+  Invocation.generateCC1CommandLine(GeneratedArgs, *this);
+
+  ASSERT_THAT(GeneratedArgs, Not(Contains(StrEq("-fdebug-pass-manager"))));
+  ASSERT_THAT(GeneratedArgs, Not(Contains(StrEq("-fno-debug-pass-manager"))));
+}
+
+TEST_F(CommandLineTest, BoolOptionCC1ViaLetPresentPos) {
+  const char *Args[] = {"-fdebug-pass-manager"};
+
+  CompilerInvocation::CreateFromArgs(Invocation, Args, *Diags);
+
+  ASSERT_FALSE(Diags->hasErrorOccurred());
+  ASSERT_TRUE(Invocation.getCodeGenOpts().DebugPassManager);
+
+  Invocation.generateCC1CommandLine(GeneratedArgs, *this);
+
+  ASSERT_THAT(GeneratedArgs, Contains(StrEq("-fdebug-pass-manager")));
+  ASSERT_THAT(GeneratedArgs, Not(Contains(StrEq("-fno-debug-pass-manager"))));
+}
+
+TEST_F(CommandLineTest, BoolOptionCC1ViaLetPresentNeg) {
+  const char *Args[] = {"-fno-debug-pass-manager"};
+
+  CompilerInvocation::CreateFromArgs(Invocation, Args, *Diags);
+
+  ASSERT_FALSE(Diags->hasErrorOccurred());
+  ASSERT_FALSE(Invocation.getCodeGenOpts().DebugPassManager);
+
+  Invocation.generateCC1CommandLine(GeneratedArgs, *this);
+
+  ASSERT_THAT(GeneratedArgs, Not(Contains(StrEq("-fno-debug-pass-manager"))));
+  ASSERT_THAT(GeneratedArgs, Not(Contains(StrEq("-fdebug-pass-manager"))));
+}
+
 TEST_F(CommandLineTest, CanGenerateCC1CommandLineFlag) {
   const char *Args[] = {"-fmodules-strict-context-hash"};