[DWARF] Eliminate the DWARFDebugNames::Header::Padding field.

The padding field is reserved for DWARF and does not contain any useful
information. No need to read, store and report it.

Differential Revision: https://reviews.llvm.org/D73042

Author: igorkudrin

llvm/include/llvm/DebugInfo/DWARF/DWARFAcceleratorTable.h

@@ -231,7 +231,6 @@ class DWARFDebugNames : public DWARFAcceleratorTable {
   struct Header {
     uint32_t UnitLength;
     uint16_t Version;
-    uint16_t Padding;
     uint32_t CompUnitCount;
     uint32_t LocalTypeUnitCount;
     uint32_t ForeignTypeUnitCount;

llvm/lib/DebugInfo/DWARF/DWARFAcceleratorTable.cpp

@@ -366,7 +366,6 @@ void DWARFDebugNames::Header::dump(ScopedPrinter &W) const {
   DictScope HeaderScope(W, "Header");
   W.printHex("Length", UnitLength);
   W.printNumber("Version", Version);
-  W.printHex("Padding", Padding);
   W.printNumber("CU count", CompUnitCount);
   W.printNumber("Local TU count", LocalTypeUnitCount);
   W.printNumber("Foreign TU count", ForeignTypeUnitCount);
@@ -397,7 +396,8 @@ Error DWARFDebugNames::Header::extract(const DWARFDataExtractor &AS,
 
   UnitLength = AS.getU32(Offset);
   Version = AS.getU16(Offset);
-  Padding = AS.getU16(Offset);
+  // Skip padding
+  *Offset += 2;
   CompUnitCount = AS.getU32(Offset);
   LocalTypeUnitCount = AS.getU32(Offset);
   ForeignTypeUnitCount = AS.getU32(Offset);

llvm/test/DebugInfo/X86/dwarfdump-debug-names.s

@@ -98,7 +98,6 @@
 # CHECK-NEXT:   Header {
 # CHECK-NEXT:     Length: 0x60
 # CHECK-NEXT:     Version: 5
-# CHECK-NEXT:     Padding: 0x0
 # CHECK-NEXT:     CU count: 1
 # CHECK-NEXT:     Local TU count: 0
 # CHECK-NEXT:     Foreign TU count: 0
@@ -144,7 +143,6 @@
 # CHECK-NEXT:   Header {
 # CHECK-NEXT:     Length: 0x44
 # CHECK-NEXT:     Version: 5
-# CHECK-NEXT:     Padding: 0x0
 # CHECK-NEXT:     CU count: 1
 # CHECK-NEXT:     Local TU count: 0
 # CHECK-NEXT:     Foreign TU count: 0