r205368 - Partially revert r204517 and fix a different way:

[Eric Christopher]

Author: echristo
Date: Tue Apr  1 17:25:28 2014
New Revision: 205368

URL: http://llvm.org/viewvc/llvm-project?rev=205368&view=rev
Log:
Partially revert r204517 and fix a different way:

We don't want to encourage the code to emit a lexical block for
a function that needs one in order for the line table to change,
we need to grab the line information from the body of the pattern
that we were instantiated from, this code should do that.

Modify the test case to ensure that we're still looking in the
right place for all of the scopes and also that we haven't
created a lexical block where we didn't need one.

Modified:
    cfe/trunk/lib/CodeGen/CGDebugInfo.cpp
    cfe/trunk/test/CodeGenCXX/linetable-fnbegin.cpp

Modified: cfe/trunk/lib/CodeGen/CGDebugInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGDebugInfo.cpp?rev=205368&r1=205367&r2=205368&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CGDebugInfo.cpp (original)
+++ cfe/trunk/lib/CodeGen/CGDebugInfo.cpp Tue Apr  1 17:25:28 2014
@@ -2497,14 +2497,25 @@ void CGDebugInfo::EmitFunctionStart(Glob
   FnBeginRegionCount.push_back(LexicalBlockStack.size());
 
   const Decl *D = GD.getDecl();
-  // Function may lack declaration in source code if it is created by Clang
-  // CodeGen (examples: _GLOBAL__I_a, __cxx_global_array_dtor, thunk).
+
+  // Use the location of the start of the function to determine where
+  // the function definition is located. By default use the location
+  // of the declaration as the location for the subprogram. A function
+  // may lack a declaration in the source code if it is created by code
+  // gen. (examples: _GLOBAL__I_a, __cxx_global_array_dtor, thunk).
   bool HasDecl = (D != 0);
-  // Use the location of the declaration.
   SourceLocation Loc;
-  if (HasDecl)
+  if (HasDecl) {
     Loc = D->getLocation();
 
+    // If this is a function specialization then use the pattern body
+    // as the location for the function.
+    if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D))
+      if (const FunctionDecl *SpecDecl = FD->getTemplateInstantiationPattern())
+        if (SpecDecl->hasBody(SpecDecl))
+          Loc = SpecDecl->getLocation();
+  }
+
   unsigned Flags = 0;
   llvm::DIFile Unit = getOrCreateFile(Loc);
   llvm::DIDescriptor FDContext(Unit);
@@ -2585,8 +2596,6 @@ void CGDebugInfo::EmitFunctionStart(Glob
   // Push the function onto the lexical block stack.
   llvm::MDNode *SPN = SP;
   LexicalBlockStack.push_back(SPN);
-  // Initialize PrevLoc to the location of the function header.
-  PrevLoc = Loc;
 
   if (HasDecl)
     RegionMap[D] = llvm::WeakVH(SP);

Modified: cfe/trunk/test/CodeGenCXX/linetable-fnbegin.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/linetable-fnbegin.cpp?rev=205368&r1=205367&r2=205368&view=diff
==============================================================================
--- cfe/trunk/test/CodeGenCXX/linetable-fnbegin.cpp (original)
+++ cfe/trunk/test/CodeGenCXX/linetable-fnbegin.cpp Tue Apr  1 17:25:28 2014
@@ -3,10 +3,13 @@
 // right header file.
 // CHECK: define{{.*}}bar
 // CHECK-NOT: define
-// CHECK: ret {{.*}}, !dbg ![[DBG:.*]]
-// CHECK: ![[HPP:.*]] = metadata !{metadata !"./template.hpp",
-// CHECK: ![[DBG]] = metadata !{i32 23, i32 0, metadata ![[BLOCK:.*]], null}
-// CHECK: ![[BLOCK]] = metadata !{{{.*}}, metadata ![[HPP]], {{.*}}} ; [ DW_TAG_lexical_block ]
+// CHECK: ret {{.*}}, !dbg [[DBG:.*]]
+// CHECK: [[HPP:.*]] = metadata !{metadata !"./template.hpp",
+// CHECK: [[SP:.*]] = metadata !{i32 786478, metadata [[HPP]], metadata !"_ZTS3FooIiE", metadata !"bar", metadata !"bar", metadata !"_ZN3FooIiE3barEv", i32 22, metadata !8, i1 false, i1 true, i32 0, i32 0, null, i32 256, i1 false, i32 (%class.Foo*)* @_ZN3FooIiE3barEv, null, metadata !7, metadata !2, i32 22} ; [ DW_TAG_subprogram ] [line 22] [def] [bar]
+// We shouldn't need a lexical block for this function.
+// CHECK: [[DBG]] = metadata !{i32 23, i32 0, metadata [[SP]], null}
+
+
 # 1 "./template.h" 1
 template <typename T>
 class Foo {