From 9e0dae166f9616e6b33b1bc7d8f493cb5b5e4f1b Mon Sep 17 00:00:00 2001
From: David Blaikie <dblaikie@gmail.com>
Date: Tue, 9 Sep 2014 22:56:36 +0000
Subject: [PATCH] Remove DwarfDebug::PrevSection, PrevCU is sufficient for
 handling address range holes.

PrevSection/PrevCU are used to detect holes in the address range of a CU
to ensure the DW_AT_ranges does not include those holes. When we see a
function with no debug info, though it may be in the same range as the
prior and subsequent functions, there should be a gap in the CU's
ranges. By setting PrevCU to null in that case, the range would not be
extended to cover the gap.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217466 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/AsmPrinter/DwarfDebug.cpp | 2 --
 lib/CodeGen/AsmPrinter/DwarfDebug.h   | 7 -------
 lib/CodeGen/AsmPrinter/DwarfUnit.cpp  | 9 +++------
 3 files changed, 3 insertions(+), 15 deletions(-)

diff --git a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 2f0e8181ed5..663ebef250b 100644
--- a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -1667,7 +1667,6 @@ void DwarfDebug::endFunction(const MachineFunction *MF) {
     // If we don't have a lexical scope for this function then there will
     // be a hole in the range information. Keep note of this by setting the
     // previously used section to nullptr.
-    PrevSection = nullptr;
     PrevCU = nullptr;
     CurFn = nullptr;
     return;
@@ -1710,7 +1709,6 @@ void DwarfDebug::endFunction(const MachineFunction *MF) {
   // Add the range of this function to the list of ranges for the CU.
   RangeSpan Span(FunctionBeginSym, FunctionEndSym);
   TheCU.addRange(std::move(Span));
-  PrevSection = Asm->getCurrentSection();
   PrevCU = &TheCU;
 
   // Clear debug info
diff --git a/lib/CodeGen/AsmPrinter/DwarfDebug.h b/lib/CodeGen/AsmPrinter/DwarfDebug.h
index 5c33d34559b..67615dc9fe0 100644
--- a/lib/CodeGen/AsmPrinter/DwarfDebug.h
+++ b/lib/CodeGen/AsmPrinter/DwarfDebug.h
@@ -243,10 +243,6 @@ class DwarfDebug : public AsmPrinterHandler {
   // If nonnull, stores the current machine instruction we're processing.
   const MachineInstr *CurMI;
 
-  // If nonnull, stores the section that the previous function was allocated to
-  // emitting.
-  const MCSection *PrevSection;
-
   // If nonnull, stores the CU in which the previous subprogram was contained.
   const DwarfCompileUnit *PrevCU;
 
@@ -631,9 +627,6 @@ public:
   /// Returns the section symbol for the .debug_loc section.
   MCSymbol *getDebugLocSym() const { return DwarfDebugLocSectionSym; }
 
-  /// Returns the previous section that was emitted into.
-  const MCSection *getPrevSection() const { return PrevSection; }
-
   /// Returns the previous CU that was being updated
   const DwarfCompileUnit *getPrevCU() const { return PrevCU; }
 
diff --git a/lib/CodeGen/AsmPrinter/DwarfUnit.cpp b/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
index c995e8bd244..3797831506f 100644
--- a/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
@@ -2044,16 +2044,13 @@ void DwarfUnit::addRange(RangeSpan Range) {
     // check the current section and CU against the previous section and CU we
     // emitted into and the subprogram was contained within. If these are the
     // same then extend our current range, otherwise add this as a new range.
-    if (CURanges.size() == 0 ||
-        this != DD->getPrevCU() ||
-        Asm->getCurrentSection() != DD->getPrevSection()) {
+    if (CURanges.empty() || this != DD->getPrevCU() ||
+        (&CURanges.back().getEnd()->getSection() !=
+         &Range.getEnd()->getSection())) {
       CURanges.push_back(Range);
       return;
     }
 
-    assert(&(CURanges.back().getEnd()->getSection()) ==
-               &(Range.getEnd()->getSection()) &&
-           "We can only append to a range in the same section!");
     CURanges.back().setEnd(Range.getEnd());
   }
 }