Apply llvm fix for assertion failure compiling recent libc++

Merge commit c7c84b90879f from llvm git (by Adrian Prantl):

  [DwarfDebug] Refuse to emit DW_OP_LLVM_arg values wider than 64 bits

  DwarfExpression::addUnsignedConstant(const APInt &Value) only supports
  wider-than-64-bit values when it is used to emit a top-level DWARF
  expression representing the location of a variable. Before this change,
  it was possible to call addUnsignedConstant on >64 bit values within a
  subexpression when substituting DW_OP_LLVM_arg values.

  This can trigger an assertion failure (e.g. PR52584, PR52333) when it
  happens in a fragment (DW_OP_LLVM_fragment) expression, as
  addUnsignedConstant on >64 bit values splits the constant into separate
  DW_OP_pieces, which modifies DwarfExpression::OffsetInBits.

  This change papers over the assertion errors by bailing on overly wide
  DW_OP_LLVM_arg values. A more comprehensive fix might be to be to split
  wide values into pointer-sized fragments.

  [0] https://github.com/llvm/llvm-project/blob/e71fa03/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp#L799-L805

  Patch by Ricky Zhou!

  Differential Revision: https://reviews.llvm.org/D115343

MFC after:	3 days

3 files changed, 33 insertions, 22 deletions

diff --git a/contrib/llvm-project/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp b/contrib/llvm-project/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
index 7edc44c48bbd..a3bf4be09fbe 100644
--- a/contrib/llvm-project/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
+++ b/contrib/llvm-project/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
@@ -779,7 +779,7 @@ DIE *DwarfCompileUnit::constructVariableDIEImpl(const DbgVariable &DV,
     const TargetRegisterInfo &TRI = *Asm->MF->getSubtarget().getRegisterInfo();
 
     auto AddEntry = [&](const DbgValueLocEntry &Entry,
-                                            DIExpressionCursor &Cursor) {
+                        DIExpressionCursor &Cursor) {
       if (Entry.isLocation()) {
         if (!DwarfExpr.addMachineRegExpression(TRI, Cursor,
                                                Entry.getLoc().getReg()))
@@ -788,11 +788,19 @@ DIE *DwarfCompileUnit::constructVariableDIEImpl(const DbgVariable &DV,
         // If there is an expression, emit raw unsigned bytes.
         DwarfExpr.addUnsignedConstant(Entry.getInt());
       } else if (Entry.isConstantFP()) {
+        // DwarfExpression does not support arguments wider than 64 bits
+        // (see PR52584).
+        // TODO: Consider chunking expressions containing overly wide
+        // arguments into separate pointer-sized fragment expressions.
         APInt RawBytes = Entry.getConstantFP()->getValueAPF().bitcastToAPInt();
-        DwarfExpr.addUnsignedConstant(RawBytes);
+        if (RawBytes.getBitWidth() > 64)
+          return false;
+        DwarfExpr.addUnsignedConstant(RawBytes.getZExtValue());
       } else if (Entry.isConstantInt()) {
         APInt RawBytes = Entry.getConstantInt()->getValue();
-        DwarfExpr.addUnsignedConstant(RawBytes);
+        if (RawBytes.getBitWidth() > 64)
+          return false;
+        DwarfExpr.addUnsignedConstant(RawBytes.getZExtValue());
       } else if (Entry.isTargetIndexLocation()) {
         TargetIndexLocation Loc = Entry.getTargetIndexLocation();
         // TODO TargetIndexLocation is a target-independent. Currently only the
@@ -805,11 +813,12 @@ DIE *DwarfCompileUnit::constructVariableDIEImpl(const DbgVariable &DV,
       return true;
     };
 
-    DwarfExpr.addExpression(
-        std::move(Cursor),
-        [&](unsigned Idx, DIExpressionCursor &Cursor) -> bool {
-          return AddEntry(DVal->getLocEntries()[Idx], Cursor);
-        });
+    if (!DwarfExpr.addExpression(
+            std::move(Cursor),
+            [&](unsigned Idx, DIExpressionCursor &Cursor) -> bool {
+              return AddEntry(DVal->getLocEntries()[Idx], Cursor);
+            }))
+      return VariableDie;
 
     // Now attach the location information to the DIE.
     addBlock(*VariableDie, dwarf::DW_AT_location, DwarfExpr.finalize());
diff --git a/contrib/llvm-project/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp b/contrib/llvm-project/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
index 6409c39e7849..37407c98e75f 100644
--- a/contrib/llvm-project/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
+++ b/contrib/llvm-project/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
@@ -463,15 +463,14 @@ static bool isMemoryLocation(DIExpressionCursor ExprCursor) {
   return true;
 }
 
-void DwarfExpression::addExpression(DIExpressionCursor &&ExprCursor,
-                                    unsigned FragmentOffsetInBits) {
+void DwarfExpression::addExpression(DIExpressionCursor &&ExprCursor) {
   addExpression(std::move(ExprCursor),
                 [](unsigned Idx, DIExpressionCursor &Cursor) -> bool {
                   llvm_unreachable("unhandled opcode found in expression");
                 });
 }
 
-void DwarfExpression::addExpression(
+bool DwarfExpression::addExpression(
     DIExpressionCursor &&ExprCursor,
     llvm::function_ref<bool(unsigned, DIExpressionCursor &)> InsertArg) {
   // Entry values can currently only cover the initial register location,
@@ -496,7 +495,7 @@ void DwarfExpression::addExpression(
     case dwarf::DW_OP_LLVM_arg:
       if (!InsertArg(Op->getArg(0), ExprCursor)) {
         LocationKind = Unknown;
-        return;
+        return false;
       }
       break;
     case dwarf::DW_OP_LLVM_fragment: {
@@ -527,7 +526,7 @@ void DwarfExpression::addExpression(
       setSubRegisterPiece(0, 0);
       // Reset the location description kind.
       LocationKind = Unknown;
-      return;
+      return true;
     }
     case dwarf::DW_OP_plus_uconst:
       assert(!isRegisterLocation());
@@ -630,6 +629,8 @@ void DwarfExpression::addExpression(
   if (isImplicitLocation() && !isParameterValue())
     // Turn this into an implicit location description.
     addStackValue();
+
+  return true;
 }
 
 /// add masking operations to stencil out a subregister.
diff --git a/contrib/llvm-project/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h b/contrib/llvm-project/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
index 513e9072309e..e605fe2f7d39 100644
--- a/contrib/llvm-project/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
+++ b/contrib/llvm-project/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
@@ -340,16 +340,17 @@ public:
   /// create one if necessary.
   unsigned getOrCreateBaseType(unsigned BitSize, dwarf::TypeKind Encoding);
 
+  /// Emit all remaining operations in the DIExpressionCursor. The
+  /// cursor must not contain any DW_OP_LLVM_arg operations.
+  void addExpression(DIExpressionCursor &&Expr);
+
   /// Emit all remaining operations in the DIExpressionCursor.
-  ///
-  /// \param FragmentOffsetInBits     If this is one fragment out of multiple
-  ///                                 locations, this is the offset of the
-  ///                                 fragment inside the entire variable.
-  void addExpression(DIExpressionCursor &&Expr,
-                     unsigned FragmentOffsetInBits = 0);
-  void
-  addExpression(DIExpressionCursor &&Expr,
-                llvm::function_ref<bool(unsigned, DIExpressionCursor &)> InsertArg);
+  /// DW_OP_LLVM_arg operations are resolved by calling (\p InsertArg).
+  //
+  /// \return false if any call to (\p InsertArg) returns false.
+  bool addExpression(
+      DIExpressionCursor &&Expr,
+      llvm::function_ref<bool(unsigned, DIExpressionCursor &)> InsertArg);
 
   /// If applicable, emit an empty DW_OP_piece / DW_OP_bit_piece to advance to
   /// the fragment described by \c Expr.