Replace the -unwind-tables option with a per function flag. This is more

LTO friendly as we can now correctly merge files compiled with or without
-fasynchronous-unwind-tables.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@132033 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 31 insertions, 5 deletions

diff --git a/include/llvm/Attributes.h b/include/llvm/Attributes.h
index da6188b1a8..57c84357ae 100644
--- a/include/llvm/Attributes.h
+++ b/include/llvm/Attributes.h
@@ -67,6 +67,20 @@ const Attributes StackAlignment  = 7<<26; ///< Alignment of stack for
                                           ///alignstack(1))
 const Attributes Hotpatch    = 1<<29;     ///< Function should have special
                                           ///'hotpatch' sequence in prologue
+const Attributes UWTable     = 1<<30;     ///< Function must be in a unwind
+                                          ///table
+
+/// Note that uwtable is about the ABI or the user mandating an entry in the
+/// unwind table. The nounwind attribute is about an exception passing by the
+/// function.
+/// In a theoretical system that uses tables for profiling and sjlj for
+/// exceptions, they would be fully independent. In a normal system that
+/// uses tables for both, the semantics are:
+/// nil                = Needs an entry because an exception might pass by.
+/// nounwind           = No need for an entry
+/// ehframe            = Needs an entry because the ABI says so and because
+///                      an exception might pass by.
+/// ehframe + nounwind = Needs an entry because the ABI says so.
 
 /// @brief Attributes that only apply to function parameters.
 const Attributes ParameterOnly = ByVal | Nest | StructRet | NoCapture;
@@ -76,7 +90,7 @@ const Attributes ParameterOnly = ByVal | Nest | StructRet | NoCapture;
 const Attributes FunctionOnly = NoReturn | NoUnwind | ReadNone | ReadOnly |
   NoInline | AlwaysInline | OptimizeForSize | StackProtect | StackProtectReq |
   NoRedZone | NoImplicitFloat | Naked | InlineHint | StackAlignment |
-  Hotpatch;
+  Hotpatch | UWTable;
 
 /// @brief Parameter attributes that do not apply to vararg call arguments.
 const Attributes VarArgsIncompatible = StructRet;
diff --git a/include/llvm/Function.h b/include/llvm/Function.h
index b34a6b2542..9319a5b39e 100644
--- a/include/llvm/Function.h
+++ b/include/llvm/Function.h
@@ -253,6 +253,22 @@ public:
     else removeFnAttr(Attribute::NoUnwind);
   }
 
+  /// @brief True if the ABI mandates this function be in a unwind table.
+  bool hasUWTable() const {
+    return hasFnAttr(Attribute::UWTable);
+  }
+  void setHasUWTable(bool HasUWTable = true) {
+    if (HasUWTable)
+      addFnAttr(Attribute::UWTable);
+    else
+      removeFnAttr(Attribute::UWTable);
+  }
+
+  /// @brief True if this function needs in a unwind table.
+  bool needsUnwindTableEntry() const {
+    return hasUWTable() || !doesNotThrow();
+  }
+
   /// @brief Determine if the function returns a structure through first 
   /// pointer argument.
   bool hasStructRetAttr() const {
diff --git a/include/llvm/Target/TargetOptions.h b/include/llvm/Target/TargetOptions.h
index 62190c166e..beed039d1d 100644
--- a/include/llvm/Target/TargetOptions.h
+++ b/include/llvm/Target/TargetOptions.h
@@ -125,10 +125,6 @@ namespace llvm {
   /// flag is hidden and is only for debugging the debug info.
   extern bool JITEmitDebugInfoToDisk;
 
-  /// UnwindTablesMandatory - This flag indicates that unwind tables should
-  /// be emitted for all functions.
-  extern bool UnwindTablesMandatory;
-
   /// GuaranteedTailCallOpt - This flag is enabled when -tailcallopt is
   /// specified on the commandline. When the flag is on, participating targets
   /// will perform tail call optimization on all calls which use the fastcc