[llvm] [BOLT] Add validation for direct call/branch targets, bypassing invalid functions (PR #165406)

[Maksim Panchenko via llvm-commits]

================
@@ -1900,6 +1910,35 @@ bool BinaryFunction::scanExternalRefs() {
   return Success;
 }
 
+bool BinaryFunction::validateInternalBranches() {
+  if (!isSimple() || TrapsOnEntry)
+    return true;
+
+  for (const auto &KV : Labels) {
+    MCSymbol *Label = KV.second;
+    if (getSecondaryEntryPointSymbol(Label))
+      continue;
+
+    const uint32_t Offset = KV.first;
+    // Skip empty functions and out-of-bounds offsets,
+    // as they may not be disassembled.
+    if (!Offset || (Offset > getSize()))
+      continue;
+
+    if (!getInstructionAtOffset(Offset) ||
+        isInConstantIsland(getAddress() + Offset)) {
+      BC.outs() << "BOLT-WARNING: corrupted control flow detected in function "
+                << *this << ", an internal branch/call targets an invalid "
----------------
maksfb wrote:

nit:
```suggestion
                << *this << ": an internal branch/call targets an invalid "
```

https://github.com/llvm/llvm-project/pull/165406