Reapply "DebugInfo: Generalize debug info location handling"

Originally committed in r224385 and reverted in r224441 due to concerns
this change might've introduced a crash. Turns out this change fixes the
crash introduced by one of my earlier more specific location handling
changes (those specific fixes are reverted by this patch, in favor of
the more general solution).

Original commit message:

This is a more scalable (fixed in mostly one place, rather than many
places that will need constant improvement/maintenance) solution to
several commits I've made recently to increase source fidelity for
subexpressions.

This resetting had to be done at the DebugLoc level (not the
SourceLocation level) to preserve scoping information (if the resetting
was done with CGDebugInfo::EmitLocation, it would've caused the tail end
of an expression's codegen to end up in a potentially different scope
than the start, even though it was at the same source location). The
drawback to this is that it might leave CGDebugInfo out of sync. Ideally
CGDebugInfo shouldn't have a duplicate sense of the current
SourceLocation, but for now it seems it does... - I don't think I'm
going to tackle removing that just now.

I expect this'll probably cause some more buildbot fallout & I'll
investigate that as it comes up.

Also these sort of improvements might be starting to show a weakness/bug
in LLVM's line table handling: we don't correctly emit is_stmt for
statements, we just put it on every line table entry. This means one
statement split over multiple lines appears as multiple 'statements' and
two statements on one line (without column info) are treated as one
statement.

I don't think we have any IR representation of statements that would
help us distinguish these cases and identify the beginning of each
statement - so that might be something we need to add (possibly to the
lexical scope chain - a scope for each statement). This does cause some
problems for GDB and possibly other DWARF consumers.

llvm-svn: 224941

1 files changed, 9 insertions, 27 deletions

diff --git a/clang/lib/CodeGen/CGDebugInfo.h b/clang/lib/CodeGen/CGDebugInfo.h
index 9649e296160..274cbc4f365 100644
--- a/clang/lib/CodeGen/CGDebugInfo.h
+++ b/clang/lib/CodeGen/CGDebugInfo.h
@@ -448,27 +448,16 @@ private:
   }
 };
 
-/// SaveAndRestoreLocation - An RAII object saves the current location
-/// and automatically restores it to the original value.
-class SaveAndRestoreLocation {
+class ApplyDebugLocation {
 protected:
-  SourceLocation SavedLoc;
-  CGDebugInfo *DI;
-  CGBuilderTy &Builder;
-public:
-  SaveAndRestoreLocation(CodeGenFunction &CGF, CGBuilderTy &B);
-  /// Autorestore everything back to normal.
-  ~SaveAndRestoreLocation();
-};
+  llvm::DebugLoc OriginalLocation;
+  CodeGenFunction &CGF;
 
-/// NoLocation - An RAII object that temporarily disables debug
-/// locations. This is useful for emitting instructions that should be
-/// counted towards the function prologue.
-class NoLocation : public SaveAndRestoreLocation {
 public:
-  NoLocation(CodeGenFunction &CGF, CGBuilderTy &B);
-  /// Autorestore everything back to normal.
-  ~NoLocation();
+  ApplyDebugLocation(CodeGenFunction &CGF,
+                     SourceLocation TemporaryLocation = SourceLocation(),
+                     bool ForceColumnInfo = false);
+  ~ApplyDebugLocation();
 };
 
 /// ArtificialLocation - An RAII object that temporarily switches to
@@ -482,16 +471,9 @@ public:
 /// This is necessary because passing an empty SourceLocation to
 /// CGDebugInfo::setLocation() will result in the last valid location
 /// being reused.
-class ArtificialLocation : public SaveAndRestoreLocation {
+class ArtificialLocation : public ApplyDebugLocation {
 public:
-  ArtificialLocation(CodeGenFunction &CGF, CGBuilderTy &B);
-
-  /// Set the current location to line 0, but within the current scope
-  /// (= the top of the LexicalBlockStack).
-  void Emit();
-
-  /// Autorestore everything back to normal.
-  ~ArtificialLocation();
+  ArtificialLocation(CodeGenFunction &CGF);
 };