DebugInfo: New metadata representation for global variables.

This patch reverses the edge from DIGlobalVariable to GlobalVariable.
This will allow us to more easily preserve debug info metadata when
manipulating global variables.

Fixes PR30362. A program for upgrading test cases is attached to that
bug.

Differential Revision: http://reviews.llvm.org/D20147

llvm-svn: 281284

1 files changed, 29 insertions, 8 deletions

diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index db82766..2504ce7 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -2679,14 +2679,35 @@ std::error_code BitcodeReader::parseMetadata(bool ModuleLevel) {
         return error("Invalid record");
 
       IsDistinct = Record[0];
-      MetadataList.assignValue(
-          GET_OR_DISTINCT(DIGlobalVariable,
-                          (Context, getMDOrNull(Record[1]),
-                           getMDString(Record[2]), getMDString(Record[3]),
-                           getMDOrNull(Record[4]), Record[5],
-                           getDITypeRefOrNull(Record[6]), Record[7], Record[8],
-                           getMDOrNull(Record[9]), getMDOrNull(Record[10]))),
-          NextMetadataNo++);
+
+      // Upgrade old metadata, which stored a global variable reference or a
+      // ConstantInt here.
+      Metadata *Expr = getMDOrNull(Record[9]);
+      GlobalVariable *Attach = nullptr;
+      if (auto *CMD = dyn_cast_or_null<ConstantAsMetadata>(Expr)) {
+        if (auto *GV = dyn_cast<GlobalVariable>(CMD->getValue())) {
+          Attach = GV;
+          Expr = nullptr;
+        } else if (auto *CI = dyn_cast<ConstantInt>(CMD->getValue())) {
+          Expr = DIExpression::get(Context,
+                                   {dwarf::DW_OP_constu, CI->getZExtValue(),
+                                    dwarf::DW_OP_stack_value});
+        } else {
+          Expr = nullptr;
+        }
+      }
+
+      DIGlobalVariable *DGV = GET_OR_DISTINCT(
+          DIGlobalVariable,
+          (Context, getMDOrNull(Record[1]), getMDString(Record[2]),
+           getMDString(Record[3]), getMDOrNull(Record[4]), Record[5],
+           getDITypeRefOrNull(Record[6]), Record[7], Record[8], Expr,
+           getMDOrNull(Record[10])));
+      MetadataList.assignValue(DGV, NextMetadataNo++);
+
+      if (Attach)
+        Attach->addDebugInfo(DGV);
+
       break;
     }
     case bitc::METADATA_LOCAL_VAR: {