From 6baaad740a5abb4bfcff022a8114abb4eea66a2d Mon Sep 17 00:00:00 2001
From: Wende Tan <twd2.me@gmail.com>
Date: Tue, 10 May 2022 15:44:46 -0700
Subject: [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 | 26 ++++++++++++++++++++------
 1 file changed, 20 insertions(+), 6 deletions(-)

(limited to 'llvm/lib/Bitcode/Writer/BitcodeWriter.cpp')

diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
index dcfe12a..1288c91 100644
--- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -19,6 +19,7 @@
 #include "llvm/ADT/None.h"
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/SmallVector.h"
@@ -3365,7 +3366,7 @@ void ModuleBitcodeWriter::writeFunction(
   bool NeedsMetadataAttachment = F.hasMetadata();
 
   DILocation *LastDL = nullptr;
-  SmallPtrSet<Function *, 4> BlockAddressUsers;
+  SmallSetVector<Function *, 4> BlockAddressUsers;
 
   // Finally, emit all the instructions, in order.
   for (const BasicBlock &BB : F) {
@@ -3401,11 +3402,24 @@ void ModuleBitcodeWriter::writeFunction(
     }
 
     if (BlockAddress *BA = BlockAddress::lookup(&BB)) {
-      for (User *U : BA->users()) {
-        if (auto *I = dyn_cast<Instruction>(U)) {
-          Function *P = I->getParent()->getParent();
-          if (P != &F)
-            BlockAddressUsers.insert(P);
+      SmallVector<Value *, 16> BlockAddressUsersStack { BA };
+      SmallPtrSet<Value *, 16> BlockAddressUsersVisited { BA };
+
+      while (!BlockAddressUsersStack.empty()) {
+        Value *V = BlockAddressUsersStack.pop_back_val();
+
+        for (User *U : V->users()) {
+          if ((isa<ConstantAggregate>(U) || isa<ConstantExpr>(U)) &&
+              !BlockAddressUsersVisited.contains(U)) {
+            BlockAddressUsersStack.push_back(U);
+            BlockAddressUsersVisited.insert(U);
+          }
+
+          if (auto *I = dyn_cast<Instruction>(U)) {
+            Function *P = I->getParent()->getParent();
+            if (P != &F)
+              BlockAddressUsers.insert(P);
+          }
         }
       }
     }
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