[BOLT] Account for FDE functions when calculating max function size

Summary:
When we calculate maximum function size we only used to rely on the
symbol table information, and ignore function info coming from FDEs.
Invalid maximum function size can lead to code emission over
the code of neighbouring function.

Fix this by considering FDE functions when determining the maximum
function size.

(cherry picked from FBD6025613)

bolt/RewriteInstance.cpp

@@ -1351,12 +1351,14 @@ void RewriteInstance::disassemblePLT() {
 }
 
 void RewriteInstance::adjustFunctionBoundaries() {
-  for (auto &BFI : BinaryFunctions) {
-    auto &Function = BFI.second;
-
-    // Check if there's a symbol with a larger address in the same section.
-    // If there is - it determines the maximum size for the current function,
-    // otherwise, it is the size of containing section the defines it.
+  for (auto BFI = BinaryFunctions.begin(), BFE = BinaryFunctions.end();
+       BFI != BFE; ++BFI) {
+    auto &Function = BFI->second;
+
+    // Check if there's a symbol or a function with a larger address in the
+    // same section. If there is - it determines the maximum size for the
+    // current function. Otherwise, it is the size of a containing section
+    // the defines it.
     //
     // NOTE: ignore some symbols that could be tolerated inside the body
     //       of a function.
@@ -1387,22 +1389,21 @@ void RewriteInstance::adjustFunctionBoundaries() {
       ? InputFile->section_end()
       : NextSymRefI->second.getSection();
 
-    uint64_t MaxSize;
-    if (NextSymRefI != FileSymRefs.end() &&
-        NextSymRefI->second.getSection() &&
-        *NextSymRefI->second.getSection() != InputFile->section_end() &&
-        **NextSymRefI->second.getSection() == Function.getSection()) {
-      MaxSize = NextSymRefI->first - Function.getAddress();
-    } else {
-      // Function runs till the end of the containing section.
-      uint64_t SectionEnd = Function.getSection().getAddress() +
-                            Function.getSection().getSize();
-      assert((NextSymRefI == FileSymRefs.end() ||
-              NextSymRefI->first >= SectionEnd) &&
-             "different sections should not overlap");
-      MaxSize = SectionEnd - Function.getAddress();
+    // Function runs at most till the end of the containing section.
+    uint64_t NextObjectAddress = Function.getSection().getAddress() +
+                                 Function.getSection().getSize();
+    // Or till the next object marked by a symbol.
+    if (NextSymRefI != FileSymRefs.end()) {
+      NextObjectAddress = std::min(NextSymRefI->first, NextObjectAddress);
+    }
+    // Or till the next function not marked by a symbol.
+    if (std::next(BFI) != BFE) {
+      const auto &NextFunction = std::next(BFI)->second;
+      NextObjectAddress = std::min(NextFunction.getAddress(),
+                                   NextObjectAddress);
     }
 
+    const auto MaxSize = NextObjectAddress - Function.getAddress();
     if (MaxSize < Function.getSize()) {
       errs() << "BOLT-ERROR: symbol seen in the middle of the function "
              << Function << ". Skipping.\n";