Allow DWARFFormValue::extractValue to be called with a null CU.

Currently FormValues are only used for attributes of DIEs and thus
uers always have a CU lying around when calling into the FormValue
API.
Accelerator tables encode their information using the same Forms
as the attributes, thus it is natural to use DWARFFormValue to
extract/dump them. There is no CU in that case though. Allow the
API to be called with a null CU arguemnt by making the RelocMap
lookup conditional on the CU pointer validity. And document this
new behvior in the header. (Test coverage for this use of the API
comes in the DwarfAccelTable support patch)

llvm-svn: 221835

2 files changed, 24 insertions, 15 deletions

diff --git a/llvm/include/llvm/DebugInfo/DWARFFormValue.h b/llvm/include/llvm/DebugInfo/DWARFFormValue.h
index 162b1deec0f..5bb6d1b9ddb 100644
--- a/llvm/include/llvm/DebugInfo/DWARFFormValue.h
+++ b/llvm/include/llvm/DebugInfo/DWARFFormValue.h
@@ -57,6 +57,13 @@ public:
   bool isFormClass(FormClass FC) const;
 
   void dump(raw_ostream &OS, const DWARFUnit *U) const;
+
+  /// \brief extracts a value in data at offset *offset_ptr.
+  ///
+  /// The passed DWARFUnit is allowed to be nullptr, in which
+  /// case no relocation processing will be performed and some
+  /// kind of forms that depend on Unit information are disallowed.
+  /// \returns wether the extraction succeeded.
   bool extractValue(DataExtractor data, uint32_t *offset_ptr,
                     const DWARFUnit *u);
   bool isInlinedCStr() const {
diff --git a/llvm/lib/DebugInfo/DWARFFormValue.cpp b/llvm/lib/DebugInfo/DWARFFormValue.cpp
index 0a478613dae..69b97710a09 100644
--- a/llvm/lib/DebugInfo/DWARFFormValue.cpp
+++ b/llvm/lib/DebugInfo/DWARFFormValue.cpp
@@ -139,6 +139,8 @@ bool DWARFFormValue::extractValue(DataExtractor data, uint32_t *offset_ptr,
     switch (Form) {
     case DW_FORM_addr:
     case DW_FORM_ref_addr: {
+      if (!cu)
+        return false;
       uint16_t AddrSize =
           (Form == DW_FORM_addr)
               ? cu->getAddressByteSize()
@@ -179,8 +181,10 @@ bool DWARFFormValue::extractValue(DataExtractor data, uint32_t *offset_ptr,
       break;
     case DW_FORM_data4:
     case DW_FORM_ref4: {
-      RelocAddrMap::const_iterator AI = cu->getRelocMap()->find(*offset_ptr);
       Value.uval = data.getU32(offset_ptr);
+      if (!cu)
+        break;
+      RelocAddrMap::const_iterator AI = cu->getRelocMap()->find(*offset_ptr-4);
       if (AI != cu->getRelocMap()->end())
         Value.uval += AI->second.second;
       break;
@@ -193,13 +197,12 @@ bool DWARFFormValue::extractValue(DataExtractor data, uint32_t *offset_ptr,
       Value.sval = data.getSLEB128(offset_ptr);
       break;
     case DW_FORM_strp: {
-      RelocAddrMap::const_iterator AI
-        = cu->getRelocMap()->find(*offset_ptr);
-      if (AI != cu->getRelocMap()->end()) {
-        const std::pair<uint8_t, int64_t> &R = AI->second;
-        Value.uval = data.getU32(offset_ptr) + R.second;
-      } else
-        Value.uval = data.getU32(offset_ptr);
+      Value.uval = data.getU32(offset_ptr);
+      if (!cu)
+        break;
+      RelocAddrMap::const_iterator AI = cu->getRelocMap()->find(*offset_ptr-4);
+      if (AI != cu->getRelocMap()->end())
+        Value.uval += AI->second.second;
       break;
     }
     case DW_FORM_udata:
@@ -215,13 +218,12 @@ bool DWARFFormValue::extractValue(DataExtractor data, uint32_t *offset_ptr,
       break;
     case DW_FORM_sec_offset: {
       // FIXME: This is 64-bit for DWARF64.
-      RelocAddrMap::const_iterator AI
-        = cu->getRelocMap()->find(*offset_ptr);
-      if (AI != cu->getRelocMap()->end()) {
-        const std::pair<uint8_t, int64_t> &R = AI->second;
-        Value.uval = data.getU32(offset_ptr) + R.second;
-      } else
-        Value.uval = data.getU32(offset_ptr);
+      Value.uval = data.getU32(offset_ptr);
+      if (!cu)
+        break;
+      RelocAddrMap::const_iterator AI = cu->getRelocMap()->find(*offset_ptr-4);
+      if (AI != cu->getRelocMap()->end())
+        Value.uval +=  AI->second.second;
       break;
     }
     case DW_FORM_flag_present: