[DWARF] Handle the DW_OP_entry_value operand

Add the IR and the AsmPrinter parts for handling of the DW_OP_entry_values
DWARF operation.

([11/13] Introduce the debug entry values.)

Co-authored-by: Ananth Sowda <asowda@cisco.com>
Co-authored-by: Nikola Prica <nikola.prica@rt-rk.com>
Co-authored-by: Ivan Baev <ibaev@cisco.com>

Differential Revision: https://reviews.llvm.org/D60866

llvm-svn: 364542

6 files changed, 53 insertions, 5 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DbgEntityHistoryCalculator.cpp b/llvm/lib/CodeGen/AsmPrinter/DbgEntityHistoryCalculator.cpp
index 2435daa8861..ddd60575b6c 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DbgEntityHistoryCalculator.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DbgEntityHistoryCalculator.cpp
@@ -41,6 +41,10 @@ using EntryIndex = DbgValueHistoryMap::EntryIndex;
 static Register isDescribedByReg(const MachineInstr &MI) {
   assert(MI.isDebugValue());
   assert(MI.getNumOperands() == 4);
+  // If the location of variable is an entry value (DW_OP_entry_value)
+  // do not consider it as a register location.
+  if (MI.getDebugExpression()->isEntryValue())
+    return 0;
   // If location of variable is described using a register (directly or
   // indirectly), this register is always a first operand.
   return MI.getOperand(0).isReg() ? MI.getOperand(0).getReg() : Register();
diff --git a/llvm/lib/CodeGen/AsmPrinter/DebugLocEntry.h b/llvm/lib/CodeGen/AsmPrinter/DebugLocEntry.h
index b489220666b..17e39b3d326 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DebugLocEntry.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DebugLocEntry.h
@@ -66,6 +66,7 @@ public:
   const ConstantInt *getConstantInt() const { return Constant.CIP; }
   MachineLocation getLoc() const { return Loc; }
   bool isFragment() const { return getExpression()->isFragment(); }
+  bool isEntryVal() const { return getExpression()->isEntryValue(); }
   const DIExpression *getExpression() const { return Expression; }
   friend bool operator==(const DbgValueLoc &, const DbgValueLoc &);
   friend bool operator<(const DbgValueLoc &, const DbgValueLoc &);
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 8e842f08bc0..71bb2b0858c 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -1999,9 +1999,9 @@ void DwarfDebug::emitDebugLocEntry(ByteStreamer &Streamer,
   }
 }
 
-static void emitDebugLocValue(const AsmPrinter &AP, const DIBasicType *BT,
-                              const DbgValueLoc &Value,
-                              DwarfExpression &DwarfExpr) {
+void DwarfDebug::emitDebugLocValue(const AsmPrinter &AP, const DIBasicType *BT,
+                                   const DbgValueLoc &Value,
+                                   DwarfExpression &DwarfExpr) {
   auto *DIExpr = Value.getExpression();
   DIExpressionCursor ExprCursor(DIExpr);
   DwarfExpr.addFragmentOffset(DIExpr);
@@ -2017,6 +2017,12 @@ static void emitDebugLocValue(const AsmPrinter &AP, const DIBasicType *BT,
     if (Location.isIndirect())
       DwarfExpr.setMemoryLocationKind();
     DIExpressionCursor Cursor(DIExpr);
+
+    if (DIExpr->isEntryValue()) {
+      DwarfExpr.setEntryValueFlag();
+      DwarfExpr.addEntryValueExpression(Cursor);
+    }
+
     const TargetRegisterInfo &TRI = *AP.MF->getSubtarget().getRegisterInfo();
     if (!DwarfExpr.addMachineRegExpression(TRI, Cursor, Location.getReg()))
       return;
@@ -2048,11 +2054,11 @@ void DebugLocEntry::finalize(const AsmPrinter &AP,
            "fragments are expected to be sorted");
 
     for (auto Fragment : Values)
-      emitDebugLocValue(AP, BT, Fragment, DwarfExpr);
+      DwarfDebug::emitDebugLocValue(AP, BT, Fragment, DwarfExpr);
 
   } else {
     assert(Values.size() == 1 && "only fragments may have >1 value");
-    emitDebugLocValue(AP, BT, Value, DwarfExpr);
+    DwarfDebug::emitDebugLocValue(AP, BT, Value, DwarfExpr);
   }
   DwarfExpr.finalize();
 }
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h
index 012013901e6..3ac474e2bdd 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h
@@ -52,6 +52,7 @@ class ByteStreamer;
 class DebugLocEntry;
 class DIE;
 class DwarfCompileUnit;
+class DwarfExpression;
 class DwarfTypeUnit;
 class DwarfUnit;
 class LexicalScope;
@@ -735,6 +736,10 @@ public:
 
   void addSectionLabel(const MCSymbol *Sym);
   const MCSymbol *getSectionLabel(const MCSection *S);
+
+  static void emitDebugLocValue(const AsmPrinter &AP, const DIBasicType *BT,
+                                const DbgValueLoc &Value,
+                                DwarfExpression &DwarfExpr);
 };
 
 } // end namespace llvm
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
index d483a30e499..2858afaa1cf 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
@@ -248,6 +248,10 @@ bool DwarfExpression::addMachineRegExpression(const TargetRegisterInfo &TRI,
         addReg(Reg.DwarfRegNo, Reg.Comment);
       addOpPiece(Reg.Size);
     }
+
+    if (isEntryValue() && DwarfVersion >= 4)
+      emitOp(dwarf::DW_OP_stack_value);
+
     DwarfRegs.clear();
     return true;
   }
@@ -296,6 +300,19 @@ bool DwarfExpression::addMachineRegExpression(const TargetRegisterInfo &TRI,
   return true;
 }
 
+void DwarfExpression::addEntryValueExpression(DIExpressionCursor &ExprCursor) {
+  auto Op = ExprCursor.take();
+  assert(Op && Op->getOp() == dwarf::DW_OP_entry_value);
+  assert(!isMemoryLocation() &&
+         "We don't support entry values of memory locations yet");
+
+  if (DwarfVersion >= 5)
+    emitOp(dwarf::DW_OP_entry_value);
+  else
+    emitOp(dwarf::DW_OP_GNU_entry_value);
+  emitUnsigned(Op->getArg(0));
+}
+
 /// Assuming a well-formed expression, match "DW_OP_deref* DW_OP_LLVM_fragment?".
 static bool isMemoryLocation(DIExpressionCursor ExprCursor) {
   while (ExprCursor) {
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
index 3a9347a3e0a..ec2ef6e575f 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
@@ -119,6 +119,9 @@ protected:
   /// The kind of location description being produced.
   enum { Unknown = 0, Register, Memory, Implicit };
 
+  /// The flags of location description being produced.
+  enum { EntryValue = 1 };
+
   unsigned LocationKind : 3;
   unsigned LocationFlags : 2;
   unsigned DwarfVersion : 4;
@@ -140,6 +143,10 @@ public:
     return LocationKind == Implicit;
   }
 
+  bool isEntryValue() const {
+    return LocationFlags & EntryValue;
+  }
+
   Optional<uint8_t> TagOffset;
 
 protected:
@@ -252,6 +259,11 @@ public:
     LocationKind = Memory;
   }
 
+  /// Lock this down to become an entry value location.
+  void setEntryValueFlag() {
+    LocationFlags |= EntryValue;
+  }
+
   /// Emit a machine register location. As an optimization this may also consume
   /// the prefix of a DwarfExpression if a more efficient representation for
   /// combining the register location and the first operation exists.
@@ -266,6 +278,9 @@ public:
                                DIExpressionCursor &Expr, unsigned MachineReg,
                                unsigned FragmentOffsetInBits = 0);
 
+  /// Emit entry value dwarf operation.
+  void addEntryValueExpression(DIExpressionCursor &ExprCursor);
+
   /// Emit all remaining operations in the DIExpressionCursor.
   ///
   /// \param FragmentOffsetInBits     If this is one fragment out of multiple