[LLDB] - Add support for DW_FORM_implicit_const.

LLDB does not support this DWARF5 form atm.
At least gcc emits it in some cases when doing optimization
for abbreviations.

As far I can tell, clang does not support it yet, though
the rest LLVM code already knows about it.

The patch adds the support.

Differential revision: https://reviews.llvm.org/D52689

llvm-svn: 344328

8 files changed, 63 insertions, 51 deletions

diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFAbbreviationDeclaration.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DWARFAbbreviationDeclaration.cpp
index a765be0b46d..d78b9ab10f5 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFAbbreviationDeclaration.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFAbbreviationDeclaration.cpp
@@ -41,9 +41,13 @@ bool DWARFAbbreviationDeclaration::Extract(const DWARFDataExtractor &data,
     while (data.ValidOffset(*offset_ptr)) {
       dw_attr_t attr = data.GetULEB128(offset_ptr);
       dw_form_t form = data.GetULEB128(offset_ptr);
+      DWARFFormValue::ValueType val;
+
+      if (form == DW_FORM_implicit_const)
+        val.value.sval = data.GetULEB128(offset_ptr);
 
       if (attr && form)
-        m_attributes.push_back(DWARFAttribute(attr, form));
+        m_attributes.push_back(DWARFAttribute(attr, form, val));
       else
         break;
     }
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFAbbreviationDeclaration.h b/lldb/source/Plugins/SymbolFile/DWARF/DWARFAbbreviationDeclaration.h
index b2296c455d6..afce52558f4 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFAbbreviationDeclaration.h
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFAbbreviationDeclaration.h
@@ -35,20 +35,11 @@ public:
   dw_form_t GetFormByIndex(uint32_t idx) const {
     return m_attributes.size() > idx ? m_attributes[idx].get_form() : 0;
   }
-  bool GetAttrAndFormByIndex(uint32_t idx, dw_attr_t &attr,
-                             dw_form_t &form) const {
-    if (m_attributes.size() > idx) {
-      m_attributes[idx].get(attr, form);
-      return true;
-    }
-    attr = form = 0;
-    return false;
-  }
 
-  // idx is assumed to be valid when calling GetAttrAndFormByIndexUnchecked()
-  void GetAttrAndFormByIndexUnchecked(uint32_t idx, dw_attr_t &attr,
-                                      dw_form_t &form) const {
-    m_attributes[idx].get(attr, form);
+  // idx is assumed to be valid when calling GetAttrAndFormByIndex()
+  void GetAttrAndFormValueByIndex(uint32_t idx, dw_attr_t &attr,
+                                  DWARFFormValue &form_value) const {
+    m_attributes[idx].get(attr, form_value.FormRef(), form_value.ValueRef());
   }
   dw_form_t GetFormByIndexUnchecked(uint32_t idx) const {
     return m_attributes[idx].get_form();
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFAttribute.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DWARFAttribute.cpp
index 2586d1f1853..dd830eb7b9d 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFAttribute.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFAttribute.cpp
@@ -26,10 +26,10 @@ uint32_t DWARFAttributes::FindAttributeIndex(dw_attr_t attr) const {
   return UINT32_MAX;
 }
 
-void DWARFAttributes::Append(const DWARFUnit *cu,
-                             dw_offset_t attr_die_offset, dw_attr_t attr,
-                             dw_form_t form) {
-  AttributeValue attr_value = {cu, attr_die_offset, {attr, form}};
+void DWARFAttributes::Append(const DWARFUnit *cu, dw_offset_t attr_die_offset,
+                             dw_attr_t attr, dw_form_t form) {
+  AttributeValue attr_value = {
+      cu, attr_die_offset, {attr, form, DWARFFormValue::ValueType()}};
   m_infos.push_back(attr_value);
 }
 
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFAttribute.h b/lldb/source/Plugins/SymbolFile/DWARF/DWARFAttribute.h
index db4324cf772..2399861d7fc 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFAttribute.h
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFAttribute.h
@@ -11,15 +11,17 @@
 #define SymbolFileDWARF_DWARFAttribute_h_
 
 #include "DWARFDefines.h"
+#include "DWARFFormValue.h"
 #include "llvm/ADT/SmallVector.h"
 #include <vector>
 
 class DWARFUnit;
-class DWARFFormValue;
 
 class DWARFAttribute {
 public:
-  DWARFAttribute(dw_attr_t attr, dw_form_t form) : m_attr(attr), m_form(form) {}
+  DWARFAttribute(dw_attr_t attr, dw_form_t form,
+                 DWARFFormValue::ValueType value)
+      : m_attr(attr), m_form(form), m_value(value) {}
 
   void set(dw_attr_t attr, dw_form_t form) {
     m_attr = attr;
@@ -29,9 +31,11 @@ public:
   void set_form(dw_form_t form) { m_form = form; }
   dw_attr_t get_attr() const { return m_attr; }
   dw_form_t get_form() const { return m_form; }
-  void get(dw_attr_t &attr, dw_form_t &form) const {
+  void get(dw_attr_t &attr, dw_form_t &form,
+           DWARFFormValue::ValueType &val) const {
     attr = m_attr;
     form = m_form;
+    val = m_value;
   }
   bool operator==(const DWARFAttribute &rhs) const {
     return m_attr == rhs.m_attr && m_form == rhs.m_form;
@@ -43,6 +47,7 @@ public:
 protected:
   dw_attr_t m_attr;
   dw_form_t m_form;
+  DWARFFormValue::ValueType m_value;
 };
 
 class DWARFAttributes {
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfoEntry.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfoEntry.cpp
index f42164deafc..55917842770 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfoEntry.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfoEntry.cpp
@@ -174,6 +174,10 @@ bool DWARFDebugInfoEntry::FastExtract(
               debug_info_data.GetU32(&offset);
             break;
 
+          case DW_FORM_implicit_const:
+            form_size = 0;
+            break;
+
           default:
             *offset_ptr = m_offset;
             return false;
@@ -233,15 +237,14 @@ bool DWARFDebugInfoEntry::Extract(SymbolFileDWARF *dwarf2Data,
 
         // Skip all data in the .debug_info for the attributes
         const uint32_t numAttributes = abbrevDecl->NumAttributes();
-        uint32_t i;
-        dw_attr_t attr;
-        dw_form_t form;
-        for (i = 0; i < numAttributes; ++i) {
-          abbrevDecl->GetAttrAndFormByIndexUnchecked(i, attr, form);
+        for (uint32_t i = 0; i < numAttributes; ++i) {
+          DWARFFormValue form_value(cu);
+          dw_attr_t attr;
+          abbrevDecl->GetAttrAndFormValueByIndex(i, attr, form_value);
+          dw_form_t form = form_value.Form();
 
           if (isCompileUnitTag &&
               ((attr == DW_AT_entry_pc) || (attr == DW_AT_low_pc))) {
-            DWARFFormValue form_value(cu, form);
             if (form_value.ExtractValue(debug_info_data, &offset)) {
               if (attr == DW_AT_low_pc || attr == DW_AT_entry_pc)
                 const_cast<DWARFUnit *>(cu)->SetBaseAddress(
@@ -287,6 +290,7 @@ bool DWARFDebugInfoEntry::Extract(SymbolFileDWARF *dwarf2Data,
 
               // 0 sized form
               case DW_FORM_flag_present:
+              case DW_FORM_implicit_const:
                 form_size = 0;
                 break;
 
@@ -417,14 +421,13 @@ bool DWARFDebugInfoEntry::GetDIENamesAndRanges(
       return false;
 
     const uint32_t numAttributes = abbrevDecl->NumAttributes();
-    uint32_t i;
-    dw_attr_t attr;
-    dw_form_t form;
     bool do_offset = false;
 
-    for (i = 0; i < numAttributes; ++i) {
-      abbrevDecl->GetAttrAndFormByIndexUnchecked(i, attr, form);
-      DWARFFormValue form_value(cu, form);
+    for (uint32_t i = 0; i < numAttributes; ++i) {
+      DWARFFormValue form_value(cu);
+      dw_attr_t attr;
+      abbrevDecl->GetAttrAndFormValueByIndex(i, attr, form_value);
+
       if (form_value.ExtractValue(debug_info_data, &offset)) {
         switch (attr) {
         case DW_AT_low_pc:
@@ -614,14 +617,13 @@ void DWARFDebugInfoEntry::Dump(SymbolFileDWARF *dwarf2Data,
 
         // Dump all data in the .debug_info for the attributes
         const uint32_t numAttributes = abbrevDecl->NumAttributes();
-        uint32_t i;
-        dw_attr_t attr;
-        dw_form_t form;
-        for (i = 0; i < numAttributes; ++i) {
-          abbrevDecl->GetAttrAndFormByIndexUnchecked(i, attr, form);
+        for (uint32_t i = 0; i < numAttributes; ++i) {
+          DWARFFormValue form_value(cu);
+          dw_attr_t attr;
+          abbrevDecl->GetAttrAndFormValueByIndex(i, attr, form_value);
 
           DumpAttribute(dwarf2Data, cu, debug_info_data, &offset, s, attr,
-                        form);
+                        form_value);
         }
 
         const DWARFDebugInfoEntry *child = GetFirstChild();
@@ -671,23 +673,21 @@ void DWARFDebugInfoEntry::DumpLocation(SymbolFileDWARF *dwarf2Data,
 void DWARFDebugInfoEntry::DumpAttribute(
     SymbolFileDWARF *dwarf2Data, const DWARFUnit *cu,
     const DWARFDataExtractor &debug_info_data, lldb::offset_t *offset_ptr,
-    Stream &s, dw_attr_t attr, dw_form_t form) {
+    Stream &s, dw_attr_t attr, DWARFFormValue &form_value) {
   bool show_form = s.GetFlags().Test(DWARFDebugInfo::eDumpFlag_ShowForm);
 
   s.Printf("            ");
   s.Indent(DW_AT_value_to_name(attr));
 
   if (show_form) {
-    s.Printf("[%s", DW_FORM_value_to_name(form));
+    s.Printf("[%s", DW_FORM_value_to_name(form_value.Form()));
   }
 
-  DWARFFormValue form_value(cu, form);
-
   if (!form_value.ExtractValue(debug_info_data, offset_ptr))
     return;
 
   if (show_form) {
-    if (form == DW_FORM_indirect) {
+    if (form_value.Form() == DW_FORM_indirect) {
       s.Printf(" [%s]", DW_FORM_value_to_name(form_value.Form()));
     }
 
@@ -794,11 +794,11 @@ size_t DWARFDebugInfoEntry::GetAttributes(
           cu->GetAddressByteSize(), cu->IsDWARF64());
 
     const uint32_t num_attributes = abbrevDecl->NumAttributes();
-    uint32_t i;
-    dw_attr_t attr;
-    dw_form_t form;
-    for (i = 0; i < num_attributes; ++i) {
-      abbrevDecl->GetAttrAndFormByIndexUnchecked(i, attr, form);
+    for (uint32_t i = 0; i < num_attributes; ++i) {
+      DWARFFormValue form_value(cu);
+      dw_attr_t attr;
+      abbrevDecl->GetAttrAndFormValueByIndex(i, attr, form_value);
+      const dw_form_t form = form_value.Form();
 
       // If we are tracking down DW_AT_specification or DW_AT_abstract_origin
       // attributes, the depth will be non-zero. We need to omit certain
@@ -819,7 +819,6 @@ size_t DWARFDebugInfoEntry::GetAttributes(
       }
 
       if ((attr == DW_AT_specification) || (attr == DW_AT_abstract_origin)) {
-        DWARFFormValue form_value(cu, form);
         if (form_value.ExtractValue(debug_info_data, &offset)) {
           dw_offset_t die_offset = form_value.Reference();
           DWARFDIE spec_die =
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfoEntry.h b/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfoEntry.h
index 97cb3046eb3..33f679c4c39 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfoEntry.h
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfoEntry.h
@@ -178,7 +178,7 @@ public:
   DumpAttribute(SymbolFileDWARF *dwarf2Data, const DWARFUnit *cu,
                 const lldb_private::DWARFDataExtractor &debug_info_data,
                 lldb::offset_t *offset_ptr, lldb_private::Stream &s,
-                dw_attr_t attr, dw_form_t form);
+                dw_attr_t attr, DWARFFormValue &form_value);
   // This one dumps the comp unit name, objfile name and die offset for this die
   // so the stream S.
   void DumpLocation(SymbolFileDWARF *dwarf2Data, DWARFUnit *cu,
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFFormValue.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DWARFFormValue.cpp
index c3d001cef9c..d2032044d13 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFFormValue.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFFormValue.cpp
@@ -154,6 +154,9 @@ DWARFFormValue::GetFixedFormSizesForAddressSize(uint8_t addr_size,
 
 DWARFFormValue::DWARFFormValue() : m_cu(NULL), m_form(0), m_value() {}
 
+DWARFFormValue::DWARFFormValue(const DWARFUnit *cu)
+    : m_cu(cu), m_form(0), m_value() {}
+
 DWARFFormValue::DWARFFormValue(const DWARFUnit *cu, dw_form_t form)
     : m_cu(cu), m_form(form), m_value() {}
 
@@ -165,6 +168,9 @@ void DWARFFormValue::Clear() {
 
 bool DWARFFormValue::ExtractValue(const DWARFDataExtractor &data,
                                   lldb::offset_t *offset_ptr) {
+  if (m_form == DW_FORM_implicit_const)
+    return true;
+
   bool indirect = false;
   bool is_block = false;
   m_value.data = NULL;
@@ -366,6 +372,7 @@ bool DWARFFormValue::SkipValue(dw_form_t form,
 
   // 0 bytes values (implied from DW_FORM)
   case DW_FORM_flag_present:
+  case DW_FORM_implicit_const:
     return true;
 
     // 1 byte values
@@ -822,6 +829,7 @@ bool DWARFFormValue::FormIsSupported(dw_form_t form) {
     case DW_FORM_ref_sig8:
     case DW_FORM_GNU_str_index:
     case DW_FORM_GNU_addr_index:
+    case DW_FORM_implicit_const:
       return true;
     default:
       break;
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFFormValue.h b/lldb/source/Plugins/SymbolFile/DWARF/DWARFFormValue.h
index b4e40f8ccc0..3fd725cf944 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFFormValue.h
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFFormValue.h
@@ -56,12 +56,17 @@ public:
   };
 
   DWARFFormValue();
+  DWARFFormValue(const DWARFUnit *cu);
   DWARFFormValue(const DWARFUnit *cu, dw_form_t form);
   const DWARFUnit *GetCompileUnit() const { return m_cu; }
   void SetCompileUnit(const DWARFUnit *cu) { m_cu = cu; }
   dw_form_t Form() const { return m_form; }
+  dw_form_t& FormRef() { return m_form; }
   void SetForm(dw_form_t form) { m_form = form; }
   const ValueType &Value() const { return m_value; }
+  ValueType &ValueRef() { return m_value; }
+  void SetValue(const ValueType &val) { m_value = val; }
+
   void Dump(lldb_private::Stream &s) const;
   bool ExtractValue(const lldb_private::DWARFDataExtractor &data,
                     lldb::offset_t *offset_ptr);