[llvm/DWARF] Return section offset from DWARFUnit::get{Loc,Rng}listOffset

Summary:
Currently these function return the raw content of the appropriate table
header, which means they are relative to the DW_AT_{loc,rng}list_base,
and one has to relocate them in order to do anything.

This changes the functions to perform the relocation themselves, which
seems more clearer, particularly as they are sitting right next to the
find{Rng,Loc}listFromOffset functions, but one *cannot* simply take the
result of these functions and take pass them there.

The only effect of this patch is to change what value is dumped for the
DW_AT_ranges attribute, which I think is for the better, as previously
the values appeared to point into thin air.

(The main reason I am looking at this is because I was trying to
implement equivalent functionality in lldb's DWARFUnit, and was stumped
by this behavior.

Reviewers: dblaikie, JDevlieghere, aprantl

Subscribers: hiraditya, llvm-commits, SouraVX

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D71006

include/llvm/DebugInfo/DWARF/DWARFUnit.h

@@ -427,14 +427,18 @@ public:
   /// an entry in the rangelist table's offset array and is supplied by
   /// DW_FORM_rnglistx.
   Optional<uint64_t> getRnglistOffset(uint32_t Index) {
-    if (RngListTable)
+    if (!RngListTable)
-      return RngListTable->getOffsetEntry(Index);
+      return None;
+    if (Optional<uint64_t> Off = RngListTable->getOffsetEntry(Index))
+      return *Off + RangeSectionBase;
     return None;
   }
 
   Optional<uint64_t> getLoclistOffset(uint32_t Index) {
-    if (LoclistTableHeader)
+    if (!LoclistTableHeader)
-      return LoclistTableHeader->getOffsetEntry(Index);
+      return None;
+    if (Optional<uint64_t> Off = LoclistTableHeader->getOffsetEntry(Index))
+      return *Off + getLocSectionBase();
     return None;
   }
   Expected<DWARFAddressRangesVector> collectAddressRanges();

lib/DebugInfo/DWARF/DWARFDie.cpp

@@ -91,7 +91,7 @@ static void dumpLocation(raw_ostream &OS, DWARFFormValue &FormValue,
       FormValue.dump(OS, DumpOpts);
 
       if (auto LoclistOffset = U->getLoclistOffset(Offset))
-        Offset = *LoclistOffset + U->getLocSectionBase();
+        Offset = *LoclistOffset;
       else
         return;
     }

lib/DebugInfo/DWARF/DWARFUnit.cpp

@@ -629,7 +629,7 @@ DWARFUnit::findRnglistFromOffset(uint64_t Offset) {
 Expected<DWARFAddressRangesVector>
 DWARFUnit::findRnglistFromIndex(uint32_t Index) {
   if (auto Offset = getRnglistOffset(Index))
-    return findRnglistFromOffset(*Offset + RangeSectionBase);
+    return findRnglistFromOffset(*Offset);
 
   if (RngListTable)
     return createStringError(errc::invalid_argument,

test/DebugInfo/X86/dwarfdump-rnglists-dwarf64.s

@@ -196,14 +196,14 @@ Range1_end:
 # CHECK-NOT:  Compile Unit:
 # CHECK:      DW_TAG_compile_unit
 # CHECK-NEXT: DW_AT_rnglists_base [DW_FORM_sec_offset]  (0x00000014)
-# CHECK-NEXT: DW_AT_ranges [DW_FORM_rnglistx] (indexed (0x1) rangelist = 0x00000020
+# CHECK-NEXT: DW_AT_ranges [DW_FORM_rnglistx] (indexed (0x1) rangelist = 0x00000034
 # CHECK-NEXT: [0x0000002a, 0x00000034) ".text")
 
 # CHECK:      .debug_info.dwo contents:
 # CHECK:      Compile Unit:
 # CHECK-NOT:  contents:
 # CHECK:      DW_TAG_compile_unit
-# CHECK-NEXT: DW_AT_ranges [DW_FORM_rnglistx] (indexed (0x1) rangelist = 0x00000011
+# CHECK-NEXT: DW_AT_ranges [DW_FORM_rnglistx] (indexed (0x1) rangelist = 0x00000025
 # CHECK-NEXT: [0x0000002a, 0x00000034))
 
 #ERR: error: parsing a range list table: did not detect a valid list table with base = 0x8

test/DebugInfo/X86/dwarfdump-rnglists.s

@@ -192,14 +192,14 @@ Range1_end:
 # CHECK-NOT:  Compile Unit:
 # CHECK:      DW_TAG_compile_unit
 # CHECK-NEXT: DW_AT_rnglists_base [DW_FORM_sec_offset]  (0x0000000c)
-# CHECK-NEXT: DW_AT_ranges [DW_FORM_rnglistx] (indexed (0x1) rangelist = 0x00000018
+# CHECK-NEXT: DW_AT_ranges [DW_FORM_rnglistx] (indexed (0x1) rangelist = 0x00000024
 # CHECK-NEXT: [0x0000002a, 0x00000034) ".text")
 
 # CHECK:      .debug_info.dwo contents:
 # CHECK:      Compile Unit:
 # CHECK-NOT:  contents:
 # CHECK:      DW_TAG_compile_unit
-# CHECK-NEXT: DW_AT_ranges [DW_FORM_rnglistx] (indexed (0x1) rangelist = 0x00000009
+# CHECK-NEXT: DW_AT_ranges [DW_FORM_rnglistx] (indexed (0x1) rangelist = 0x00000015
 # CHECK-NEXT: [0x0000002a, 0x00000034))
 
 #ERR: error: parsing a range list table: did not detect a valid list table with base = 0x8

test/DebugInfo/X86/split-dwarf-v5-ranges.ll

@@ -3,7 +3,7 @@
 
 ; CHECK: .debug_info contents:
 ; CHECK: .debug_info.dwo contents:
-; CHECK: DW_AT_ranges [DW_FORM_rnglistx] (indexed (0x0) rangelist = 0x00000004
+; CHECK: DW_AT_ranges [DW_FORM_rnglistx] (indexed (0x0) rangelist = 0x00000010
 ; CHECK:          [0x0000000000000001, 0x000000000000000c) ".text"
 ; CHECK:          [0x000000000000000e, 0x0000000000000013) ".text")
 

test/tools/llvm-dwarfdump/X86/no_debug_addr.s

@@ -4,7 +4,7 @@
 ## Ensure bogus empty section names are not printed when dumping
 ## rnglists that reference debug_addr when it is not present (such as in .dwo files)
 
-# CHECK:       DW_AT_ranges [DW_FORM_rnglistx]   (indexed (0x0) rangelist = 0x00000004
+# CHECK:       DW_AT_ranges [DW_FORM_rnglistx]   (indexed (0x0) rangelist = 0x00000010
 # CHECK-NEXT:    [0x0000000000000000, 0x0000000000000001)
 # CHECK-NEXT:    [0x0000000000000000, 0x0000000000000002))