[Bitcode] Include indirect users of BlockAddresses in bitcode
authorWende Tan <twd2.me@gmail.com>
Tue, 10 May 2022 22:44:46 +0000 (15:44 -0700)
committerNick Desaulniers <ndesaulniers@google.com>
Tue, 10 May 2022 23:03:42 +0000 (16:03 -0700)
commit6baaad740a5abb4bfcff022a8114abb4eea66a2d
treece8f1f4676fa2d46d96aa0a194679525ce39e687
parentfc58d7a3261dc168fc177e54722b5ade1bb8508b
[Bitcode] Include indirect users of BlockAddresses in bitcode

The original fix (commit 23ec5782c3cc) of
https://github.com/llvm/llvm-project/issues/52787 only adds `Function`s
that have `Instruction`s that directly use `BlockAddress`es into the
bitcode (`FUNC_CODE_BLOCKADDR_USERS`).

However, in either @rickyz's original reproducing code:

```
void f(long);

__attribute__((noinline)) static void fun(long x) {
  f(x + 1);
}

void repro(void) {
  fun(({
    label:
      (long)&&label;
  }));
}
```

```
...
define dso_local void @repro() #0 {
entry:
  br label %label

label:                                            ; preds = %entry
  tail call fastcc void @fun()
  ret void
}

define internal fastcc void @fun() unnamed_addr #1 {
entry:
  tail call void @f(i64 add (i64 ptrtoint (i8* blockaddress(@repro, %label) to i64), i64 1)) #3
  ret void
}
...
```

or the xfs and overlayfs in the Linux kernel, `BlockAddress`es (e.g.,
`i8* blockaddress(@repro, %label)`) may first compose `ConstantExpr`s
(e.g., `i64 ptrtoint (i8* blockaddress(@repro, %label) to i64)`) and
then used by `Instruction`s. This case is not handled by the original
fix.

This patch adds *indirect* users of `BlockAddress`es, i.e., the
`Instruction`s using some `Constant`s which further use the
`BlockAddress`es, into the bitcode as well, by doing depth-first
searches.

Fixes: https://github.com/llvm/llvm-project/issues/52787
Fixes: 23ec5782c3cc ("[Bitcode] materialize Functions early when BlockAddress taken")

Reviewed By: nickdesaulniers

Differential Revision: https://reviews.llvm.org/D124878
llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
llvm/test/Bitcode/blockaddress-aggregate-users.ll [new file with mode: 0644]
llvm/test/Bitcode/blockaddress-expr-users.ll [new file with mode: 0644]
llvm/test/Bitcode/blockaddress-globalvalue-users.ll [new file with mode: 0644]
llvm/test/Bitcode/blockaddress-nested-users.ll [new file with mode: 0644]