DebugInfo: Add parsing support for debug_loc base address specifiers

llvm-svn: 373278
(cherry picked from commit 5ca3066)

Author: dwblaikie

llvm/include/llvm/DebugInfo/DWARF/DWARFDebugLoc.h

@@ -68,7 +68,7 @@ class DWARFDebugLoc {
   /// Return the location list at the given offset or nullptr.
   LocationList const *getLocationListAtOffset(uint64_t Offset) const;
 
-  static Expected<LocationList>
+  Expected<LocationList>
   parseOneLocationList(const DWARFDataExtractor &Data, uint64_t *Offset);
 };
 

llvm/lib/DebugInfo/DWARF/DWARFDebugLoc.cpp

@@ -101,6 +101,7 @@ DWARFDebugLoc::parseOneLocationList(const DWARFDataExtractor &Data,
 
     if (Error Err = C.takeError())
       return std::move(Err);
+
     // The end of any given location list is marked by an end of list entry,
     // which consists of a 0 for the beginning address offset and a 0 for the
     // ending address offset.
@@ -109,9 +110,12 @@ DWARFDebugLoc::parseOneLocationList(const DWARFDataExtractor &Data,
       return LL;
     }
 
-    unsigned Bytes = Data.getU16(C);
-    // A single location description describing the location of the object...
-    Data.getU8(C, E.Loc, Bytes);
+    if (E.Begin != (AddressSize == 4 ? -1U : -1ULL)) {
+      unsigned Bytes = Data.getU16(C);
+      // A single location description describing the location of the object...
+      Data.getU8(C, E.Loc, Bytes);
+    }
+
     LL.Entries.push_back(std::move(E));
   }
 }

llvm/test/tools/llvm-dwarfdump/debug_loc_base_address.s

@@ -0,0 +1,34 @@
+# RUN: llvm-mc %s -filetype obj -triple x86_64-pc-linux -o %t.o
+# RUN: llvm-dwarfdump --debug-loc %t.o | FileCheck %s
+
+# CHECK:         .debug_loc contents:
+# CHECK-NEXT:    0x00000000:
+# CHECK-NEXT:    [0xffffffffffffffff, 0x000000000000002a):
+# CHECK-NEXT:    [0x0000000000000003, 0x0000000000000007): DW_OP_consts +3, DW_OP_stack_value
+
+	.section	.debug_loc,"",@progbits
+	.quad	0xffffffffffffffff
+	.quad	42
+	.quad	3
+	.quad	7
+	.short	3                       # Loc expr size
+	.byte	17                      # DW_OP_consts
+	.byte	3                       # 3
+	.byte	159                     # DW_OP_stack_value
+	.quad	0
+	.quad	0
+	.section	.debug_abbrev,"",@progbits
+	.byte	1                       # Abbreviation Code
+	.byte	17                      # DW_TAG_compile_unit
+	.byte	0                       # DW_CHILDREN_no
+	.byte	0                       # EOM(1)
+	.byte	0                       # EOM(2)
+	.byte	0                       # EOM(3)
+	.section	.debug_info,"",@progbits
+	.long	.Ldebug_info_end0-.Ldebug_info_start0 # Length of Unit
+.Ldebug_info_start0:
+	.short	4                       # DWARF version number
+	.long	.debug_abbrev           # Offset Into Abbrev. Section
+	.byte	8                       # Address Size (in bytes)
+	.byte	1                       # Abbrev [1] DW_TAG_compile_unit
+.Ldebug_info_end0: