Cherry-pick fixes for rdar://problem/48167864

lldb/include/lldb/Core/Section.h

@@ -43,9 +43,8 @@ class SectionList {
   const_iterator begin() { return m_sections.begin(); }
   const_iterator end() { return m_sections.end(); }
 
-  SectionList();
-
-  ~SectionList();
+  /// Create an empty list.
+  SectionList() = default;
 
   SectionList &operator=(const SectionList &rhs);
 

lldb/include/lldb/Utility/Scalar.h

@@ -38,6 +38,7 @@ namespace lldb_private {
 // follows the ANSI C type promotion rules.
 class Scalar {
 public:
+  // FIXME: These are host types which seems to be an odd choice.
   enum Type {
     e_void = 0,
     e_sint,
@@ -98,30 +99,14 @@ class Scalar {
   }
   Scalar(llvm::APInt v) : m_type(), m_float(static_cast<float>(0)) {
     m_integer = llvm::APInt(v);
-    switch (m_integer.getBitWidth()) {
-    case 8:
-    case 16:
-    case 32:
-      m_type = e_sint;
-      return;
-    case 64:
-      m_type = e_slonglong;
-      return;
-    case 128:
-      m_type = e_sint128;
-      return;
-    case 256:
-      m_type = e_sint256;
-      return;
-    case 512:
-      m_type = e_sint512;
-      return;
-    }
-    lldbassert(false && "unsupported bitwidth");
+    m_type = GetBestTypeForBitSize(m_integer.getBitWidth(), true);
   }
   // Scalar(const RegisterValue& reg_value);
   virtual ~Scalar();
 
+  /// Return the most efficient Scalar::Type for the requested bit size.
+  static Type GetBestTypeForBitSize(size_t bit_size, bool sign);
+
   bool SignExtend(uint32_t bit_pos);
 
   bool ExtractBitfield(uint32_t bit_size, uint32_t bit_offset);
@@ -154,6 +139,9 @@ class Scalar {
     return (m_type >= e_sint) && (m_type <= e_long_double);
   }
 
+  /// Convert integer to \p type, limited to \p bits size.
+  void TruncOrExtendTo(Scalar::Type type, uint16_t bits);
+
   bool Promote(Scalar::Type type);
 
   bool MakeSigned();

lldb/source/Core/Section.cpp

@@ -417,10 +417,6 @@ lldb::offset_t Section::GetSectionData(DataExtractor &section_data) {
 
 #pragma mark SectionList
 
-SectionList::SectionList() : m_sections() {}
-
-SectionList::~SectionList() {}
-
 SectionList &SectionList::operator=(const SectionList &rhs) {
   if (this != &rhs)
     m_sections = rhs.m_sections;

lldb/source/Expression/DWARFExpression.cpp

@@ -2559,6 +2559,83 @@ bool DWARFExpression::Evaluate(
       stack.back().SetValueType(Value::eValueTypeScalar);
       break;
 
+    // OPCODE: DW_OP_convert
+    // OPERANDS: 1
+    //      A ULEB128 that is either a DIE offset of a
+    //      DW_TAG_base_type or 0 for the generic (pointer-sized) type.
+    //
+    // DESCRIPTION: Pop the top stack element, convert it to a
+    // different type, and push the result.
+    case DW_OP_convert: {
+      if (stack.size() < 1) {
+        if (error_ptr)
+          error_ptr->SetErrorString(
+              "Expression stack needs at least 1 item for DW_OP_convert.");
+        return false;
+      }
+      const uint64_t die_offset = opcodes.GetULEB128(&offset);
+      Scalar::Type type = Scalar::e_void;
+      uint64_t bit_size;
+      if (die_offset == 0) {
+        // The generic type has the size of an address on the target
+        // machine and an unspecified signedness. Scalar has no
+        // "unspecified signedness", so we use unsigned types.
+        if (!module_sp) {
+          if (error_ptr)
+            error_ptr->SetErrorString("No module");
+          return false;
+        }
+        bit_size = module_sp->GetArchitecture().GetAddressByteSize() * 8;
+        if (!bit_size) {
+          if (error_ptr)
+            error_ptr->SetErrorString("unspecified architecture");
+          return false;
+        }
+        type = Scalar::GetBestTypeForBitSize(bit_size, false);
+      } else {
+        // Retrieve the type DIE that the value is being converted to.
+        // FIXME: the constness has annoying ripple effects.
+        DWARFDIE die = const_cast<DWARFUnit *>(dwarf_cu)->GetDIE(die_offset);
+        if (!die) {
+          if (error_ptr)
+            error_ptr->SetErrorString("Cannot resolve DW_OP_convert type DIE");
+          return false;
+        }
+        uint64_t encoding =
+            die.GetAttributeValueAsUnsigned(DW_AT_encoding, DW_ATE_hi_user);
+        bit_size = die.GetAttributeValueAsUnsigned(DW_AT_byte_size, 0) * 8;
+        if (!bit_size)
+          bit_size = die.GetAttributeValueAsUnsigned(DW_AT_bit_size, 0);
+        if (!bit_size) {
+          if (error_ptr)
+            error_ptr->SetErrorString("Unsupported type size in DW_OP_convert");
+          return false;
+        }
+        switch (encoding) {
+        case DW_ATE_signed:
+        case DW_ATE_signed_char:
+          type = Scalar::GetBestTypeForBitSize(bit_size, true);
+          break;
+        case DW_ATE_unsigned:
+        case DW_ATE_unsigned_char:
+          type = Scalar::GetBestTypeForBitSize(bit_size, false);
+          break;
+        default:
+          if (error_ptr)
+            error_ptr->SetErrorString("Unsupported encoding in DW_OP_convert");
+          return false;
+        }
+      }
+      if (type == Scalar::e_void) {
+        if (error_ptr)
+          error_ptr->SetErrorString("Unsupported pointer size");
+        return false;
+      }
+      Scalar &top = stack.back().ResolveValue(exe_ctx);
+      top.TruncOrExtendTo(type, bit_size);
+      break;
+    }
+
     // OPCODE: DW_OP_call_frame_cfa
     // OPERANDS: None
     // DESCRIPTION: Specifies a DWARF expression that pushes the value of

lldb/source/Utility/Scalar.cpp

@@ -416,6 +416,51 @@ Scalar &Scalar::operator=(llvm::APInt rhs) {
 
 Scalar::~Scalar() = default;
 
+Scalar::Type Scalar::GetBestTypeForBitSize(size_t bit_size, bool sign) {
+  // Scalar types are always host types, hence the sizeof().
+  if (sign) {
+    if (bit_size <= sizeof(int)*8) return Scalar::e_sint;
+    if (bit_size <= sizeof(long)*8) return Scalar::e_slong;
+    if (bit_size <= sizeof(long long)*8) return Scalar::e_slonglong;
+    if (bit_size <= 128) return Scalar::e_sint128;
+    if (bit_size <= 256) return Scalar::e_sint256;
+    if (bit_size <= 512) return Scalar::e_sint512;
+  } else {
+    if (bit_size <= sizeof(unsigned int)*8) return Scalar::e_uint;
+    if (bit_size <= sizeof(unsigned long)*8) return Scalar::e_ulong;
+    if (bit_size <= sizeof(unsigned long long)*8) return Scalar::e_ulonglong;
+    if (bit_size <= 128) return Scalar::e_uint128;
+    if (bit_size <= 256) return Scalar::e_uint256;
+    if (bit_size <= 512) return Scalar::e_uint512;
+  }
+  return Scalar::e_void;
+};
+
+void Scalar::TruncOrExtendTo(Scalar::Type type, uint16_t bits) {
+  switch (type) {
+  case e_sint:
+  case e_slong:
+  case e_slonglong:
+  case e_sint128:
+  case e_sint256:
+  case e_sint512:
+    m_integer = m_integer.sextOrTrunc(bits);
+    break;
+  case e_uint:
+  case e_ulong:
+  case e_ulonglong:
+  case e_uint128:
+  case e_uint256:
+  case e_uint512:
+    m_integer = m_integer.zextOrTrunc(bits);
+    break;
+  default:
+    llvm_unreachable("Promoting a Scalar to a specific number of bits is only "
+                     "supported for integer types.");
+  }
+  m_type = type;
+}
+
 bool Scalar::Promote(Scalar::Type type) {
   bool success = false;
   switch (m_type) {