From 36375ee7a584343fabaf20630326f1848263bce6 Mon Sep 17 00:00:00 2001
From: Devang Patel <dpatel@apple.com>
Date: Tue, 17 Feb 2009 21:23:59 +0000
Subject: [PATCH] Emit debug info for bitfields.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@64815 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/llvm/Analysis/DebugInfo.h        |  9 ++++++---
 lib/Analysis/DebugInfo.cpp               | 15 ++++++++++++---
 lib/CodeGen/AsmPrinter/DwarfWriter.cpp   | 19 ++++++++++++++++++-
 test/FrontendC/2009-02-17-BitField-dbg.c | 13 +++++++++++++
 4 files changed, 49 insertions(+), 7 deletions(-)
 create mode 100644 test/FrontendC/2009-02-17-BitField-dbg.c

diff --git a/include/llvm/Analysis/DebugInfo.h b/include/llvm/Analysis/DebugInfo.h
index 164600e59d5..1aa40e7b70b 100644
--- a/include/llvm/Analysis/DebugInfo.h
+++ b/include/llvm/Analysis/DebugInfo.h
@@ -118,9 +118,9 @@ namespace llvm {
     /// code generator accepts maximum one main compile unit per module. If a
     /// module does not contain any main compile unit then the code generator 
     /// will emit multiple compile units in the output object file.
-    bool isMain() const             { return getUnsignedField(6); }
-    bool isOptimized() const         { return getUnsignedField(7); }
-    std::string getFlags() const     { return getStringField(8); }
+    bool isMain() const                { return getUnsignedField(6); }
+    bool isOptimized() const           { return getUnsignedField(7); }
+    std::string getFlags() const       { return getStringField(8); }
 
     /// Verify - Verify that a compile unit is well formed.
     bool Verify() const;
@@ -217,6 +217,9 @@ namespace llvm {
     explicit DIDerivedType(GlobalVariable *GV);
     DIType getTypeDerivedFrom() const { return getFieldAs<DIType>(9); }
 
+    /// getOriginalTypeSize - If this type is derived from a base type then
+    /// return base type size.
+    uint64_t getOriginalTypeSize() const;
     /// dump - print derived type.
     void dump() const;
   };
diff --git a/lib/Analysis/DebugInfo.cpp b/lib/Analysis/DebugInfo.cpp
index 0ec80894f11..10356e59fae 100644
--- a/lib/Analysis/DebugInfo.cpp
+++ b/lib/Analysis/DebugInfo.cpp
@@ -169,8 +169,8 @@ bool DIVariable::isVariable(unsigned Tag) {
   }
 }
 
-DIVariable::DIVariable(GlobalVariable *GV) : DIDescriptor(GV) {
-  if (GV && !isVariable(getTag()))
+DIVariable::DIVariable(GlobalVariable *gv) : DIDescriptor(gv) {
+  if (gv && !isVariable(getTag()))
     GV = 0;
 }
 
@@ -273,7 +273,16 @@ bool DIVariable::Verify() const {
   return true;
 }
 
-
+/// getOriginalTypeSize - If this type is derived from a base type then
+/// return base type size.
+uint64_t DIDerivedType::getOriginalTypeSize() const {
+  if (getTag() != dwarf::DW_TAG_member)
+    return getSizeInBits();
+  DIType BT = getTypeDerivedFrom();
+  if (BT.getTag() != dwarf::DW_TAG_base_type)
+    return getSizeInBits();
+  return BT.getSizeInBits();
+}
 
 //===----------------------------------------------------------------------===//
 // DIFactory: Basic Helpers
diff --git a/lib/CodeGen/AsmPrinter/DwarfWriter.cpp b/lib/CodeGen/AsmPrinter/DwarfWriter.cpp
index 1265b990377..5e79a812c4e 100644
--- a/lib/CodeGen/AsmPrinter/DwarfWriter.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfWriter.cpp
@@ -1873,7 +1873,24 @@ private:
 
     AddSourceLine(MemberDie, &DT);
 
-    // FIXME _ Handle bitfields
+    uint64_t Size = DT.getSizeInBits();
+    uint64_t FieldSize = DT.getOriginalTypeSize();
+
+    if (Size != FieldSize) {
+      // Handle bitfield.
+      AddUInt(MemberDie, DW_AT_byte_size, 0, DT.getOriginalTypeSize() >> 3);
+      AddUInt(MemberDie, DW_AT_bit_size, 0, DT.getSizeInBits());
+
+      uint64_t Offset = DT.getOffsetInBits();
+      uint64_t FieldOffset = Offset;
+      uint64_t AlignMask = ~(DT.getAlignInBits() - 1);
+      uint64_t HiMark = (Offset + FieldSize) & AlignMask;
+      FieldOffset = (HiMark - FieldSize);
+      Offset -= FieldOffset;
+      // Maybe we need to work from the other end.
+      if (TD->isLittleEndian()) Offset = FieldSize - (Offset + Size);
+      AddUInt(MemberDie, DW_AT_bit_offset, 0, Offset);
+    }
     DIEBlock *Block = new DIEBlock();
     AddUInt(Block, 0, DW_FORM_data1, DW_OP_plus_uconst);
     AddUInt(Block, 0, DW_FORM_udata, DT.getOffsetInBits() >> 3);
diff --git a/test/FrontendC/2009-02-17-BitField-dbg.c b/test/FrontendC/2009-02-17-BitField-dbg.c
new file mode 100644
index 00000000000..456b0a64a79
--- /dev/null
+++ b/test/FrontendC/2009-02-17-BitField-dbg.c
@@ -0,0 +1,13 @@
+// Check bitfields.
+// RUN: %llvmgcc -S -O0 -g %s -o - | llvm-as | \
+// RUN: llc --disable-fp-elim -o 2009-02-17-BitField-dbg.s -f
+// RUN: %compile_c 2009-02-17-BitField-dbg.s -o 2009-02-17-BitField-dbg.o
+// RUN: echo {ptype mystruct} > %t2
+// RUN: gdb -q -batch -n -x %t2 2009-02-17-BitField-dbg.o | \
+// RUN:   tee 2009-02-17-BitField-dbg.out | grep "int a : 4"
+
+struct {
+  int  a:4;
+  int  b:2;
+} mystruct;
+