Mark functions with uwtable(default) attribute when SEH in use.

Fix the crash in Windows runtime while unwinding the stack, as well as the GDB backtrace when SEH exception model is used. issue: eng/toolchain/gnat-llvm#249

Author: apietrek

llvm-interface/gnatllvm-codegen.adb

@@ -720,6 +720,10 @@ package body GNATLLVM.Codegen is
  Set_Module_PIC_PIE (Module, PIC_Level, PIE_Level);
  end if;
 
+ if SEH then
+ Set_Unwind_Tables (Module);
+ end if;
+
  -- ??? Replace this by a parameter in system.ads or target.atp
 
  if Target_Triple (TT_First .. TT_First + 3) = "wasm" then

llvm-interface/gnatllvm-glvalue.adb

@@ -1817,6 +1817,15 @@ package body GNATLLVM.GLValue is
  Add_Named_Attribute (+V, Name, Value, Get_Global_Context);
  end Add_Named_Attribute;
 
+ ---------------------------
+ -- Add_Uwtable_Attribute --
+ ---------------------------
+
+ procedure Add_Uwtable_Attribute (V : GL_Value) is
+ begin
+ Add_Uwtable_Attribute (+V);
+ end Add_Uwtable_Attribute;
+
  ------------------------
  -- Add_Nest_Attribute --
  ------------------------

llvm-interface/gnatllvm-glvalue.ads

@@ -1171,6 +1171,9 @@ package GNATLLVM.GLValue is
  -- Add the appropropriate Inline attributes, if any, to the LLVM
  -- function V based on the flags in Subp.
 
+ procedure Add_Uwtable_Attribute (V : GL_Value)
+ with Pre => Is_A_Function (V), Inline;
+
  procedure Add_Named_Attribute (V : GL_Value; Name, Value : String)
  with Pre => Is_A_Function (V), Inline;
 

llvm-interface/gnatllvm-subprograms.adb

@@ -2854,6 +2854,10 @@ package body GNATLLVM.Subprograms is
 
  Add_Inline_Attribute (LLVM_Func, E);
 
+ if SEH then
+ Add_Uwtable_Attribute (LLVM_Func);
+ end if;
+
  if No_Tail_Calls then
  Add_Named_Attribute (LLVM_Func, "disable-tail-calls", "true");
  end if;

llvm-interface/gnatllvm-wrapper.ads

@@ -150,6 +150,10 @@ package GNATLLVM.Wrapper is
  with Import, Convention => C,
  External_Name => "Add_No_Implicit_Float_Attribute";
 
+ procedure Add_Uwtable_Attribute (Func : Value_T)
+ with Import, Convention => C,
+ External_Name => "Add_Uwtable_Attribute";
+
  function Has_Inline_Attribute (Func : Value_T) return Boolean
  with Pre => Present (Is_A_Function (Func));
 
@@ -442,6 +446,10 @@ package GNATLLVM.Wrapper is
  (Module : Module_T; PIC : PIC_PIE_Level; PIE : PIC_PIE_Level)
  with Import, Convention => C, External_Name => "Set_Module_PIC_PIE";
 
+ procedure Set_Unwind_Tables
+ (Module : Module_T)
+ with Import, Convention => C, External_Name => "Set_Unwind_Tables";
+
  function Has_Default_PIE (Triple : String) return Boolean;
 
  function Has_SEH (Triple : String) return Boolean;

llvm-interface/llvm_wrapper.cc

@@ -159,6 +159,13 @@ Add_Inline_No_Attribute (Function *fn)
  fn->addFnAttr (Attribute::NoInline);
 }
 
+extern "C"
+void
+Add_Uwtable_Attribute (Function *fn)
+{
+ fn->setUWTableKind(UWTableKind::Default);
+}
+
 extern "C"
 void
 Add_Fn_Readonly_Attribute (Function *fn)
@@ -1196,6 +1203,13 @@ Set_Module_PIC_PIE (Module *M, int PIC, int PIE)
  M->setPIELevel(static_cast<PIELevel::Level>(PIE));
 }
 
+extern "C"
+void
+Set_Unwind_Tables (Module *M)
+{
+ M->setUwtable(UWTableKind::Default);
+}
+
 extern "C"
 bool
 Has_Default_PIE (const char *Target)