From 660daac2d0489045f2bb142a9f7eb5b7737f3594 Mon Sep 17 00:00:00 2001
From: Rafael Auler <rafaelauler@fb.com>
Date: Mon, 11 Dec 2017 17:07:56 -0800
Subject: [PATCH] [BOLT] Fix -simplify-rodata-loads wrt data chunks with relocs

Summary:
The pass was previously copying data that would change after layout
because it had a relocation at the copied address.

(cherry picked from FBD6541334)
---
 bolt/BinaryContext.cpp       | 16 ++++++++++++++++
 bolt/BinaryContext.h         |  4 ++++
 bolt/Passes/BinaryPasses.cpp |  4 ++++
 3 files changed, 24 insertions(+)

diff --git a/bolt/BinaryContext.cpp b/bolt/BinaryContext.cpp
index d1f38138bb09..02821658b973 100644
--- a/bolt/BinaryContext.cpp
+++ b/bolt/BinaryContext.cpp
@@ -525,6 +525,22 @@ void BinaryContext::removeRelocationAt(uint64_t Address) {
   Relocations.erase(RelocI);
 }
 
+const Relocation *BinaryContext::getRelocationAt(uint64_t Address) {
+  auto ContainingSection = getSectionForAddress(Address);
+  assert(ContainingSection && "cannot find section for address");
+  auto RI = SectionRelocations.find(*ContainingSection);
+  if (RI == SectionRelocations.end())
+    return nullptr;
+
+  auto &Relocations = RI->second;
+  auto RelocI = Relocations.find(
+            Relocation{Address - ContainingSection->getAddress(), 0, 0, 0, 0});
+  if (RelocI == Relocations.end())
+    return nullptr;
+
+  return &*RelocI;
+}
+
 size_t Relocation::getSizeForType(uint64_t Type) {
   switch (Type) {
   default:
diff --git a/bolt/BinaryContext.h b/bolt/BinaryContext.h
index ad4909e9f013..69b26b1d5c89 100644
--- a/bolt/BinaryContext.h
+++ b/bolt/BinaryContext.h
@@ -301,6 +301,10 @@ public:
   /// Remove registered relocation at a given \p Address.
   void removeRelocationAt(uint64_t Address);
 
+  /// Return a relocation registered at a given \p Address, or nullptr if there
+  /// is no relocation at such address.
+  const Relocation *getRelocationAt(uint64_t Address);
+
   const BinaryFunction *getFunctionForSymbol(const MCSymbol *Symbol) const {
     auto BFI = SymbolToFunctionMap.find(Symbol);
     return BFI == SymbolToFunctionMap.end() ? nullptr : BFI->second;
diff --git a/bolt/Passes/BinaryPasses.cpp b/bolt/Passes/BinaryPasses.cpp
index ddcd87974dac..6f78bb856f2c 100644
--- a/bolt/Passes/BinaryPasses.cpp
+++ b/bolt/Passes/BinaryPasses.cpp
@@ -1146,6 +1146,10 @@ bool SimplifyRODataLoads::simplifyRODataLoads(
       SectionRef DataSection = DataSectionOrErr.get();
       if (!DataSection.isReadOnly())
         continue;
+
+      if (BC.getRelocationAt(TargetAddress))
+        continue;
+
       uint32_t Offset = TargetAddress - DataSection.getAddress();
       StringRef ConstantData;
       if (std::error_code EC = DataSection.getContents(ConstantData)) {