Move the complex address expression out of DIVariable and into an extra

argument of the llvm.dbg.declare/llvm.dbg.value intrinsics.

Previously, DIVariable was a variable-length field that has an optional
reference to a Metadata array consisting of a variable number of
complex address expressions. In the case of OpPiece expressions this is
wasting a lot of storage in IR, because when an aggregate type is, e.g.,
SROA'd into all of its n individual members, the IR will contain n copies
of the DIVariable, all alike, only differing in the complex address
reference at the end.

By making the complex address into an extra argument of the
dbg.value/dbg.declare intrinsics, all of the pieces can reference the
same variable and the complex address expressions can be uniqued across
the CU, too.
Down the road, this will allow us to move other flags, such as
"indirection" out of the DIVariable, too.

The new intrinsics look like this:
declare void @llvm.dbg.declare(metadata %storage, metadata %var, metadata %expr)
declare void @llvm.dbg.value(metadata %storage, i64 %offset, metadata %var, metadata %expr)

This patch adds a new LLVM-local tag to DIExpressions, so we can detect
and pretty-print DIExpression metadata nodes.

What this patch doesn't do:

This patch does not touch the "Indirect" field in DIVariable; but moving
that into the expression would be a natural next step.

http://reviews.llvm.org/D4919
rdar://problem/17994491

Thanks to dblaikie and dexonsmith for reviewing this patch!

llvm-svn: 218778

1 files changed, 27 insertions, 45 deletions

diff --git a/llvm/lib/IR/DIBuilder.cpp b/llvm/lib/IR/DIBuilder.cpp
index a5c09b60c4f..1ab52523d73 100644
--- a/llvm/lib/IR/DIBuilder.cpp
+++ b/llvm/lib/IR/DIBuilder.cpp
@@ -1042,50 +1042,28 @@ DIVariable DIBuilder::createLocalVariable(unsigned Tag, DIDescriptor Scope,
   return RetVar;
 }
 
-/// createComplexVariable - Create a new descriptor for the specified variable
-/// which has a complex address expression for its address.
-DIVariable DIBuilder::createComplexVariable(unsigned Tag, DIDescriptor Scope,
-                                            StringRef Name, DIFile F,
-                                            unsigned LineNo,
-                                            DITypeRef Ty,
-                                            ArrayRef<Value *> Addr,
-                                            unsigned ArgNo) {
-  assert(Addr.size() > 0 && "complex address is empty");
-  Value *Elts[] = {
-    GetTagConstant(VMContext, Tag),
-    getNonCompileUnitScope(Scope),
-    MDString::get(VMContext, Name),
-    F,
-    ConstantInt::get(Type::getInt32Ty(VMContext),
-                     (LineNo | (ArgNo << 24))),
-    Ty,
-    Constant::getNullValue(Type::getInt32Ty(VMContext)),
-    Constant::getNullValue(Type::getInt32Ty(VMContext)),
-    MDNode::get(VMContext, Addr)
-  };
-  return DIVariable(MDNode::get(VMContext, Elts));
+/// createExpression - Create a new descriptor for the specified
+/// variable which has a complex address expression for its address.
+/// @param Addr        An array of complex address operations.
+DIExpression DIBuilder::createExpression(ArrayRef<Value *> Addr) {
+  SmallVector<llvm::Value *, 16> Elts;
+  Elts.push_back(GetTagConstant(VMContext, DW_TAG_expression));
+  Elts.insert(Elts.end(), Addr.begin(), Addr.end());
+  return DIExpression(MDNode::get(VMContext, Elts));
 }
 
 /// createVariablePiece - Create a descriptor to describe one part
 /// of aggregate variable that is fragmented across multiple Values.
-DIVariable DIBuilder::createVariablePiece(DIVariable Variable,
-                                          unsigned OffsetInBytes,
-                                          unsigned SizeInBytes) {
+DIExpression DIBuilder::createPieceExpression(unsigned OffsetInBytes,
+                                              unsigned SizeInBytes) {
   assert(SizeInBytes > 0 && "zero-size piece");
   Value *Addr[] = {
-    ConstantInt::get(Type::getInt32Ty(VMContext), OpPiece),
-    ConstantInt::get(Type::getInt32Ty(VMContext), OffsetInBytes),
-    ConstantInt::get(Type::getInt32Ty(VMContext), SizeInBytes)
-  };
-
-  assert((Variable->getNumOperands() == 8 || Variable.isVariablePiece()) &&
-         "variable already has a complex address");
-  SmallVector<Value *, 9> Elts;
-  for (unsigned i = 0; i < 8; ++i)
-    Elts.push_back(Variable->getOperand(i));
+      GetTagConstant(VMContext, DW_TAG_expression),
+      ConstantInt::get(Type::getInt64Ty(VMContext), dwarf::DW_OP_piece),
+      ConstantInt::get(Type::getInt64Ty(VMContext), OffsetInBytes),
+      ConstantInt::get(Type::getInt64Ty(VMContext), SizeInBytes)};
 
-  Elts.push_back(MDNode::get(VMContext, Addr));
-  return DIVariable(MDNode::get(VMContext, Elts));
+  return DIExpression(MDNode::get(VMContext, Addr));
 }
 
 /// createFunction - Create a new descriptor for the specified function.
@@ -1292,6 +1270,7 @@ DILexicalBlock DIBuilder::createLexicalBlock(DIDescriptor Scope, DIFile File,
 
 /// insertDeclare - Insert a new llvm.dbg.declare intrinsic call.
 Instruction *DIBuilder::insertDeclare(Value *Storage, DIVariable VarInfo,
+                                      DIExpression Expr,
                                       Instruction *InsertBefore) {
   assert(Storage && "no storage passed to dbg.declare");
   assert(VarInfo.isVariable() &&
@@ -1299,12 +1278,13 @@ Instruction *DIBuilder::insertDeclare(Value *Storage, DIVariable VarInfo,
   if (!DeclareFn)
     DeclareFn = Intrinsic::getDeclaration(&M, Intrinsic::dbg_declare);
 
-  Value *Args[] = { MDNode::get(Storage->getContext(), Storage), VarInfo };
+  Value *Args[] = {MDNode::get(Storage->getContext(), Storage), VarInfo, Expr};
   return CallInst::Create(DeclareFn, Args, "", InsertBefore);
 }
 
 /// insertDeclare - Insert a new llvm.dbg.declare intrinsic call.
 Instruction *DIBuilder::insertDeclare(Value *Storage, DIVariable VarInfo,
+                                      DIExpression Expr,
                                       BasicBlock *InsertAtEnd) {
   assert(Storage && "no storage passed to dbg.declare");
   assert(VarInfo.isVariable() &&
@@ -1312,7 +1292,7 @@ Instruction *DIBuilder::insertDeclare(Value *Storage, DIVariable VarInfo,
   if (!DeclareFn)
     DeclareFn = Intrinsic::getDeclaration(&M, Intrinsic::dbg_declare);
 
-  Value *Args[] = { MDNode::get(Storage->getContext(), Storage), VarInfo };
+  Value *Args[] = {MDNode::get(Storage->getContext(), Storage), VarInfo, Expr};
 
   // If this block already has a terminator then insert this intrinsic
   // before the terminator.
@@ -1325,6 +1305,7 @@ Instruction *DIBuilder::insertDeclare(Value *Storage, DIVariable VarInfo,
 /// insertDbgValueIntrinsic - Insert a new llvm.dbg.value intrinsic call.
 Instruction *DIBuilder::insertDbgValueIntrinsic(Value *V, uint64_t Offset,
                                                 DIVariable VarInfo,
+                                                DIExpression Expr,
                                                 Instruction *InsertBefore) {
   assert(V && "no value passed to dbg.value");
   assert(VarInfo.isVariable() &&
@@ -1332,15 +1313,16 @@ Instruction *DIBuilder::insertDbgValueIntrinsic(Value *V, uint64_t Offset,
   if (!ValueFn)
     ValueFn = Intrinsic::getDeclaration(&M, Intrinsic::dbg_value);
 
-  Value *Args[] = { MDNode::get(V->getContext(), V),
-                    ConstantInt::get(Type::getInt64Ty(V->getContext()), Offset),
-                    VarInfo };
+  Value *Args[] = {MDNode::get(V->getContext(), V),
+                   ConstantInt::get(Type::getInt64Ty(V->getContext()), Offset),
+                   VarInfo, Expr};
   return CallInst::Create(ValueFn, Args, "", InsertBefore);
 }
 
 /// insertDbgValueIntrinsic - Insert a new llvm.dbg.value intrinsic call.
 Instruction *DIBuilder::insertDbgValueIntrinsic(Value *V, uint64_t Offset,
                                                 DIVariable VarInfo,
+                                                DIExpression Expr,
                                                 BasicBlock *InsertAtEnd) {
   assert(V && "no value passed to dbg.value");
   assert(VarInfo.isVariable() &&
@@ -1348,8 +1330,8 @@ Instruction *DIBuilder::insertDbgValueIntrinsic(Value *V, uint64_t Offset,
   if (!ValueFn)
     ValueFn = Intrinsic::getDeclaration(&M, Intrinsic::dbg_value);
 
-  Value *Args[] = { MDNode::get(V->getContext(), V),
-                    ConstantInt::get(Type::getInt64Ty(V->getContext()), Offset),
-                    VarInfo };
+  Value *Args[] = {MDNode::get(V->getContext(), V),
+                   ConstantInt::get(Type::getInt64Ty(V->getContext()), Offset),
+                   VarInfo, Expr};
   return CallInst::Create(ValueFn, Args, "", InsertAtEnd);
 }