DebugInfo: Use the preferred location rather than the start location for expression line info

This causes things like assignment to refer to the '=' rather than the
LHS when attributing the store instruction, for example.

There were essentially 3 options for this:

* The beginning of an expression (this was the behavior prior to this
  commit). This meant that stepping through subexpressions would bounce
  around from subexpressions back to the start of the outer expression,
  etc. (eg: x + y + z would go x, y, x, z, x (the repeated 'x's would be
  where the actual addition occurred)).

* The end of an expression. This seems to be what GCC does /mostly/, and
  certainly this for function calls. This has the advantage that
  progress is always 'forwards' (never jumping backwards - except for
  independent subexpressions if they're evaluated in interesting orders,
  etc). "x + y + z" would go "x y z" with the additions occurring at y
  and z after the respective loads.
  The problem with this is that the user would still have to think
  fairly hard about precedence to realize which subexpression is being
  evaluated or which operator overload is being called in, say, an asan
  backtrace.

* The preferred location or 'exprloc'. In this case you get sort of what
  you'd expect, though it's a bit confusing in its own way due to going
  'backwards'. In this case the locations would be: "x y + z +" in
  lovely postfix arithmetic order. But this does mean that if the op+
  were an operator overload, say, and in a backtrace, the backtrace will
  point to the exact '+' that's being called, not to the end of one of
  its operands.

(actually the operator overload case doesn't work yet for other reasons,
but that's being fixed - but this at least gets scalar/complex
assignments and other plain operators right)

llvm-svn: 227027

7 files changed, 19 insertions, 6 deletions

diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index 17a8f063c5a..38a1184bd72 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -65,6 +65,10 @@ ArtificialLocation::ArtificialLocation(CodeGenFunction &CGF)
 ApplyDebugLocation::ApplyDebugLocation(CodeGenFunction &CGF,
                                        SourceLocation TemporaryLocation)
     : CGF(CGF) {
+  init(TemporaryLocation);
+}
+
+void ApplyDebugLocation::init(SourceLocation TemporaryLocation) {
   if (auto *DI = CGF.getDebugInfo()) {
     OriginalLocation = CGF.Builder.getCurrentDebugLocation();
     if (TemporaryLocation.isInvalid())
@@ -74,6 +78,11 @@ ApplyDebugLocation::ApplyDebugLocation(CodeGenFunction &CGF,
   }
 }
 
+ApplyDebugLocation::ApplyDebugLocation(CodeGenFunction &CGF, const Expr *E)
+    : CGF(CGF) {
+  init(E->getExprLoc());
+}
+
 ApplyDebugLocation::ApplyDebugLocation(CodeGenFunction &CGF, llvm::DebugLoc Loc)
     : CGF(CGF) {
   if (CGF.getDebugInfo()) {
diff --git a/clang/lib/CodeGen/CGDebugInfo.h b/clang/lib/CodeGen/CGDebugInfo.h
index bcce9000183..8e00c1b0482 100644
--- a/clang/lib/CodeGen/CGDebugInfo.h
+++ b/clang/lib/CodeGen/CGDebugInfo.h
@@ -444,6 +444,9 @@ private:
 };
 
 class ApplyDebugLocation {
+private:
+  void init(SourceLocation TemporaryLocation);
+
 protected:
   llvm::DebugLoc OriginalLocation;
   CodeGenFunction &CGF;
@@ -451,6 +454,7 @@ protected:
 public:
   ApplyDebugLocation(CodeGenFunction &CGF,
                      SourceLocation TemporaryLocation = SourceLocation());
+  ApplyDebugLocation(CodeGenFunction &CGF, const Expr *E);
   ApplyDebugLocation(CodeGenFunction &CGF, llvm::DebugLoc Loc);
   ~ApplyDebugLocation();
 };
diff --git a/clang/lib/CodeGen/CGExpr.cpp b/clang/lib/CodeGen/CGExpr.cpp
index 6fdd1104803..3a45d77e2c2 100644
--- a/clang/lib/CodeGen/CGExpr.cpp
+++ b/clang/lib/CodeGen/CGExpr.cpp
@@ -807,7 +807,7 @@ LValue CodeGenFunction::EmitCheckedLValue(const Expr *E, TypeCheckKind TCK) {
 /// length type, this is not possible.
 ///
 LValue CodeGenFunction::EmitLValue(const Expr *E) {
-  ApplyDebugLocation DL(*this, E->getLocStart());
+  ApplyDebugLocation DL(*this, E);
   switch (E->getStmtClass()) {
   default: return EmitUnsupportedLValue(E, "l-value expression");
 
@@ -3060,7 +3060,7 @@ RValue CodeGenFunction::EmitRValueForField(LValue LV,
 
 RValue CodeGenFunction::EmitCallExpr(const CallExpr *E,
                                      ReturnValueSlot ReturnValue) {
-  ApplyDebugLocation DL(*this, E->getLocStart());
+  ApplyDebugLocation DL(*this, E);
 
   // Builtins never have block type.
   if (E->getCallee()->getType()->isBlockPointerType())
diff --git a/clang/lib/CodeGen/CGExprAgg.cpp b/clang/lib/CodeGen/CGExprAgg.cpp
index 4cba4781afc..80b16dd5ba3 100644
--- a/clang/lib/CodeGen/CGExprAgg.cpp
+++ b/clang/lib/CodeGen/CGExprAgg.cpp
@@ -99,7 +99,7 @@ public:
   //===--------------------------------------------------------------------===//
 
   void Visit(Expr *E) {
-    ApplyDebugLocation DL(CGF, E->getLocStart());
+    ApplyDebugLocation DL(CGF, E);
     StmtVisitor<AggExprEmitter>::Visit(E);
   }
 
diff --git a/clang/lib/CodeGen/CGExprCXX.cpp b/clang/lib/CodeGen/CGExprCXX.cpp
index 6d63b3ae9cf..cead8a429df 100644
--- a/clang/lib/CodeGen/CGExprCXX.cpp
+++ b/clang/lib/CodeGen/CGExprCXX.cpp
@@ -1016,7 +1016,7 @@ static void EmitNewInitializer(CodeGenFunction &CGF, const CXXNewExpr *E,
                                llvm::Value *NewPtr,
                                llvm::Value *NumElements,
                                llvm::Value *AllocSizeWithoutCookie) {
-  ApplyDebugLocation DL(CGF, E->getStartLoc());
+  ApplyDebugLocation DL(CGF, E);
   if (E->isArray())
     CGF.EmitNewArrayInitializer(E, ElementType, NewPtr, NumElements,
                                 AllocSizeWithoutCookie);
diff --git a/clang/lib/CodeGen/CGExprComplex.cpp b/clang/lib/CodeGen/CGExprComplex.cpp
index 2cbd42b7ee5..b6adbf64f82 100644
--- a/clang/lib/CodeGen/CGExprComplex.cpp
+++ b/clang/lib/CodeGen/CGExprComplex.cpp
@@ -95,7 +95,7 @@ public:
   //===--------------------------------------------------------------------===//
 
   ComplexPairTy Visit(Expr *E) {
-    ApplyDebugLocation DL(CGF, E->getLocStart());
+    ApplyDebugLocation DL(CGF, E);
     return StmtVisitor<ComplexExprEmitter, ComplexPairTy>::Visit(E);
   }
 
diff --git a/clang/lib/CodeGen/CGExprScalar.cpp b/clang/lib/CodeGen/CGExprScalar.cpp
index a9cbf05da10..2e2821b6230 100644
--- a/clang/lib/CodeGen/CGExprScalar.cpp
+++ b/clang/lib/CodeGen/CGExprScalar.cpp
@@ -196,7 +196,7 @@ public:
   //===--------------------------------------------------------------------===//
 
   Value *Visit(Expr *E) {
-    ApplyDebugLocation DL(CGF, E->getLocStart());
+    ApplyDebugLocation DL(CGF, E);
     return StmtVisitor<ScalarExprEmitter, Value*>::Visit(E);
   }