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, 28 insertions, 20 deletions

diff --git a/llvm/lib/CodeGen/LiveDebugVariables.cpp b/llvm/lib/CodeGen/LiveDebugVariables.cpp
index 2790008..72d0e13 100644
--- a/llvm/lib/CodeGen/LiveDebugVariables.cpp
+++ b/llvm/lib/CodeGen/LiveDebugVariables.cpp
@@ -110,7 +110,8 @@ public:
 namespace {
 class LDVImpl;
 class UserValue {
-  const MDNode *variable; ///< The debug info variable we are part of.
+  const MDNode *Variable;   ///< The debug info variable we are part of.
+  const MDNode *Expression; ///< Any complex address expression.
   unsigned offset;        ///< Byte offset into variable.
   bool IsIndirect;        ///< true if this is a register-indirect+offset value.
   DebugLoc dl;            ///< The debug location for the variable. This is
@@ -140,11 +141,10 @@ class UserValue {
 
 public:
   /// UserValue - Create a new UserValue.
-  UserValue(const MDNode *var, unsigned o, bool i, DebugLoc L,
-            LocMap::Allocator &alloc)
-    : variable(var), offset(o), IsIndirect(i), dl(L), leader(this),
-      next(nullptr), locInts(alloc)
-  {}
+  UserValue(const MDNode *var, const MDNode *expr, unsigned o, bool i,
+            DebugLoc L, LocMap::Allocator &alloc)
+      : Variable(var), Expression(expr), offset(o), IsIndirect(i), dl(L),
+        leader(this), next(nullptr), locInts(alloc) {}
 
   /// getLeader - Get the leader of this value's equivalence class.
   UserValue *getLeader() {
@@ -158,8 +158,10 @@ public:
   UserValue *getNext() const { return next; }
 
   /// match - Does this UserValue match the parameters?
-  bool match(const MDNode *Var, unsigned Offset, bool indirect) const {
-    return Var == variable && Offset == offset && indirect == IsIndirect;
+  bool match(const MDNode *Var, const MDNode *Expr, unsigned Offset,
+             bool indirect) const {
+    return Var == Variable && Expr == Expression && Offset == offset &&
+           indirect == IsIndirect;
   }
 
   /// merge - Merge equivalence classes.
@@ -307,8 +309,8 @@ class LDVImpl {
   UVMap userVarMap;
 
   /// getUserValue - Find or create a UserValue.
-  UserValue *getUserValue(const MDNode *Var, unsigned Offset,
-                          bool IsIndirect, DebugLoc DL);
+  UserValue *getUserValue(const MDNode *Var, const MDNode *Expr,
+                          unsigned Offset, bool IsIndirect, DebugLoc DL);
 
   /// lookupVirtReg - Find the EC leader for VirtReg or null.
   UserValue *lookupVirtReg(unsigned VirtReg);
@@ -361,7 +363,7 @@ public:
 } // namespace
 
 void UserValue::print(raw_ostream &OS, const TargetMachine *TM) {
-  DIVariable DV(variable);
+  DIVariable DV(Variable);
   OS << "!\"";
   DV.printExtendedName(OS);
   OS << "\"\t";
@@ -422,19 +424,20 @@ void UserValue::mapVirtRegs(LDVImpl *LDV) {
       LDV->mapVirtReg(locations[i].getReg(), this);
 }
 
-UserValue *LDVImpl::getUserValue(const MDNode *Var, unsigned Offset,
-                                 bool IsIndirect, DebugLoc DL) {
+UserValue *LDVImpl::getUserValue(const MDNode *Var, const MDNode *Expr,
+                                 unsigned Offset, bool IsIndirect,
+                                 DebugLoc DL) {
   UserValue *&Leader = userVarMap[Var];
   if (Leader) {
     UserValue *UV = Leader->getLeader();
     Leader = UV;
     for (; UV; UV = UV->getNext())
-      if (UV->match(Var, Offset, IsIndirect))
+      if (UV->match(Var, Expr, Offset, IsIndirect))
         return UV;
   }
 
   userValues.push_back(
-      make_unique<UserValue>(Var, Offset, IsIndirect, DL, allocator));
+      make_unique<UserValue>(Var, Expr, Offset, IsIndirect, DL, allocator));
   UserValue *UV = userValues.back().get();
   Leader = UserValue::merge(Leader, UV);
   return UV;
@@ -454,7 +457,7 @@ UserValue *LDVImpl::lookupVirtReg(unsigned VirtReg) {
 
 bool LDVImpl::handleDebugValue(MachineInstr *MI, SlotIndex Idx) {
   // DBG_VALUE loc, offset, variable
-  if (MI->getNumOperands() != 3 ||
+  if (MI->getNumOperands() != 4 ||
       !(MI->getOperand(1).isReg() || MI->getOperand(1).isImm()) ||
       !MI->getOperand(2).isMetadata()) {
     DEBUG(dbgs() << "Can't handle " << *MI);
@@ -464,9 +467,11 @@ bool LDVImpl::handleDebugValue(MachineInstr *MI, SlotIndex Idx) {
   // Get or create the UserValue for (variable,offset).
   bool IsIndirect = MI->isIndirectDebugValue();
   unsigned Offset = IsIndirect ? MI->getOperand(1).getImm() : 0;
-  const MDNode *Var = MI->getOperand(2).getMetadata();
+  const MDNode *Var = MI->getDebugVariable();
+  const MDNode *Expr = MI->getDebugExpression();
   //here.
-  UserValue *UV = getUserValue(Var, Offset, IsIndirect, MI->getDebugLoc());
+  UserValue *UV =
+      getUserValue(Var, Expr, Offset, IsIndirect, MI->getDebugLoc());
   UV->addDef(Idx, MI->getOperand(0));
   return true;
 }
@@ -951,10 +956,13 @@ void UserValue::insertDebugValue(MachineBasicBlock *MBB, SlotIndex Idx,
 
   if (Loc.isReg())
     BuildMI(*MBB, I, findDebugLoc(), TII.get(TargetOpcode::DBG_VALUE),
-            IsIndirect, Loc.getReg(), offset, variable);
+            IsIndirect, Loc.getReg(), offset, Variable, Expression);
   else
     BuildMI(*MBB, I, findDebugLoc(), TII.get(TargetOpcode::DBG_VALUE))
-      .addOperand(Loc).addImm(offset).addMetadata(variable);
+        .addOperand(Loc)
+        .addImm(offset)
+        .addMetadata(Variable)
+        .addMetadata(Expression);
 }
 
 void UserValue::emitDebugValues(VirtRegMap *VRM, LiveIntervals &LIS,