MC/Mach-O/x86_64: Add a new hook for checking whether a particular section can

be diced into atoms, and adjust getAtom() to take this into account.
 - This fixes relocations to symbols in fixed size literal sections, for
   example.

llvm-svn: 103532

2 files changed, 26 insertions, 0 deletions

diff --git a/llvm/lib/MC/MCAssembler.cpp b/llvm/lib/MC/MCAssembler.cpp
index 65e3571107b..8ec927e4150 100644
--- a/llvm/lib/MC/MCAssembler.cpp
+++ b/llvm/lib/MC/MCAssembler.cpp
@@ -297,6 +297,12 @@ const MCSymbolData *MCAssembler::getAtom(const MCAsmLayout &Layout,
   if (!SD->getFragment())
     return 0;
 
+  // Non-linker visible symbols in sections which can't be atomized have no
+  // defining atom.
+  if (!getBackend().isSectionAtomizable(
+        SD->getFragment()->getParent()->getSection()))
+    return 0;
+
   // Otherwise, return the atom for the containing fragment.
   return SD->getFragment()->getAtom();
 }
diff --git a/llvm/lib/Target/X86/X86AsmBackend.cpp b/llvm/lib/Target/X86/X86AsmBackend.cpp
index b72601ae586..8ee836e1c61 100644
--- a/llvm/lib/Target/X86/X86AsmBackend.cpp
+++ b/llvm/lib/Target/X86/X86AsmBackend.cpp
@@ -259,6 +259,26 @@ public:
     const MCSectionMachO &SMO = static_cast<const MCSectionMachO&>(Section);
     return SMO.getType() == MCSectionMachO::S_CSTRING_LITERALS;
   }
+
+  virtual bool isSectionAtomizable(const MCSection &Section) const {
+    const MCSectionMachO &SMO = static_cast<const MCSectionMachO&>(Section);
+    // Fixed sized data sections are uniqued, they cannot be diced into atoms.
+    switch (SMO.getType()) {
+    default:
+      return true;
+
+    case MCSectionMachO::S_4BYTE_LITERALS:
+    case MCSectionMachO::S_8BYTE_LITERALS:
+    case MCSectionMachO::S_16BYTE_LITERALS:
+    case MCSectionMachO::S_LITERAL_POINTERS:
+    case MCSectionMachO::S_NON_LAZY_SYMBOL_POINTERS:
+    case MCSectionMachO::S_LAZY_SYMBOL_POINTERS:
+    case MCSectionMachO::S_MOD_INIT_FUNC_POINTERS:
+    case MCSectionMachO::S_MOD_TERM_FUNC_POINTERS:
+    case MCSectionMachO::S_INTERPOSING:
+      return false;
+    }
+  }
 };
 
 }