[llvm] d0c4277 - [MC][ARM] Don't create multiple .ARM.exidx associated to one .text

[Fangrui Song via llvm-commits]

Author: Fangrui Song
Date: 2020-02-25T18:18:13-08:00
New Revision: d0c4277d388628154b647a45cbc6914a1ea5a822

URL: https://github.com/llvm/llvm-project/commit/d0c4277d388628154b647a45cbc6914a1ea5a822
DIFF: https://github.com/llvm/llvm-project/commit/d0c4277d388628154b647a45cbc6914a1ea5a822.diff

LOG: [MC][ARM] Don't create multiple .ARM.exidx associated to one .text

Fixed an issue exposed by D74006.

In clang cc1as, MCContext::UseNamesOnTempLabels is true.
When parsing a .fnstart directive, FnStart gets redefined to a temporary symbol of a different name (.Ltmp0, .Ltmp1, ...).
MCContext::getELFSection() called by SwitchToEHSection() will create a different .ARM.exidx each time.

llvm-mc uses `Ctx.setUseNamesOnTempLabels(false);` and FnStart is unnamed.
MCContext::getELFSection() called by SwitchToEHSection() will reuse the same .ARM.exidx .

Reviewed By: efriedma

Differential Revision: https://reviews.llvm.org/D75095

Added: 
    

Modified: 
    llvm/lib/MC/MCContext.cpp
    llvm/lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/MC/MCContext.cpp b/llvm/lib/MC/MCContext.cpp
index 6cda18adb881..524ef44d1863 100644
--- a/llvm/lib/MC/MCContext.cpp
+++ b/llvm/lib/MC/MCContext.cpp
@@ -405,6 +405,7 @@ MCSectionELF *MCContext::getELFSection(const Twine &Section, unsigned Type,
   StringRef Group = "";
   if (GroupSym)
     Group = GroupSym->getName();
+  assert(!(LinkedToSym && LinkedToSym->getName().empty()));
   // Do the lookup, if we have a hit, return it.
   auto IterBool = ELFUniquingMap.insert(std::make_pair(
       ELFSectionKey{Section.str(), Group,

diff  --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp b/llvm/lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp
index b13188ad9a5e..ef9804ab63a5 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp
@@ -1201,7 +1201,7 @@ inline void ARMELFStreamer::SwitchToEHSection(StringRef Prefix,
     Flags |= ELF::SHF_GROUP;
   MCSectionELF *EHSection = getContext().getELFSection(
       EHSecName, Type, Flags, 0, Group, FnSection.getUniqueID(),
-      static_cast<const MCSymbolELF *>(&Fn));
+      static_cast<const MCSymbolELF *>(FnSection.getBeginSymbol()));
 
   assert(EHSection && "Failed to get the required EH section");