[PATCH] D31140: [LLVMbugs] [Bug 18710] Only generate .ARM.exidx and .ARM.extab when needed in EHABI

[Christian Bruel via Phabricator via cfe-commits]

chrib updated this revision to Diff 93631.
chrib added a dependency: D31139: [LLVMbugs] [Bug 18710] Only generate .ARM.exidx and .ARM.extab when needed with EHABI.
chrib added a comment.



1. Updating https://reviews.llvm.org/D31140: [LLVMbugs] [Bug 18710] Only generate .ARM.exidx and .ARM.extab when needed in EHABI #

Set UNTable of the language requiers an exception table.
Conservately only for ARM, necessary to emit the .cantunwind directive. But could probably be enabled for all targets.

depends on https://reviews.llvm.org/D31139


https://reviews.llvm.org/D31140

Files:
  lib/CodeGen/CodeGenModule.cpp
  lib/CodeGen/CodeGenModule.h


Index: lib/CodeGen/CodeGenModule.h
===================================================================
--- lib/CodeGen/CodeGenModule.h
+++ lib/CodeGen/CodeGenModule.h
@@ -1341,6 +1341,9 @@
   void ConstructDefaultFnAttrList(StringRef Name, bool HasOptnone,
                                   bool AttrOnCallSite,
                                   llvm::AttrBuilder &FuncAttrs);
+
+  bool needsUnwindTable();
+
 };
 }  // end namespace CodeGen
 }  // end namespace clang
Index: lib/CodeGen/CodeGenModule.cpp
===================================================================
--- lib/CodeGen/CodeGenModule.cpp
+++ lib/CodeGen/CodeGenModule.cpp
@@ -865,13 +865,25 @@
   return true;
 }
 
+// This function needs an unwind table
+bool CodeGenModule::needsUnwindTable() {
+  if (CodeGenOpts.UnwindTables)
+    return true;
+
+  llvm::Triple::ArchType Arch = Context.getTargetInfo().getTriple().getArch();
+  return hasUnwindExceptions (LangOpts) && Arch==llvm::Triple::arm;
+}
+
 void CodeGenModule::SetLLVMFunctionAttributesForDefinition(const Decl *D,
                                                            llvm::Function *F) {
   llvm::AttrBuilder B;
 
-  if (CodeGenOpts.UnwindTables)
+  // Set the attribute if the user requests it or if the language requiers it.
+  if (needsUnwindTable())
     B.addAttribute(llvm::Attribute::UWTable);
 
+  // If the module doesn't support exceptions the function cannot throw.
+  // We can have a nothrow function even if unwind tables are required.
   if (!hasUnwindExceptions(LangOpts))
     B.addAttribute(llvm::Attribute::NoUnwind);
 


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