[dsymutil] Relocate DW_TAG_label

[JDevlieghere]

Summary

dsymutil is not relocating the DW_AT_low_pc for a DW_TAG_label. This
patch fixes that and adds a test.

[aprantl]

Seems legit.

[MaggieYi]

Hi Jonas,

The label2.test failed on Windows in the line 19:

CHECK-NEXT:   DW_AT_decl_file       ("/tmp/label/label.c")

The generated DW_AT_decl_file On Windows is:

CHECK-NEXT:   DW_AT_decl_file       ("/tmp/label\label.c")   <--- Windows path separator

Could you please look at the test and make it pass on Windows as well?

For example, changing the Check line to:

CHECK-NEXT:   DW_AT_decl_file       ("/tmp/label{{[/\\]}}label.c")

Thanks,
Maggie

[thakis]

Looks like this breaks tests on windows: http://45.33.8.238/win/36016/step_11.txt

Please take a look, and revert for now if it takes a while to fix.

[MaggieYi]

Hi Jonas and Nico,

I (with Doug’s help) have committed the patch (
https://github.com/llvm/llvm-project/commit/c5109d3c7936d9c78216e0cc722c1ce0ea9246ec)
since the test failure blocked the local build. Please modify or revert the
patch if there is a better fix.

Thanks,

[JDevlieghere]

Apologies, the Windows issue must've been buried among the dwarfdump vs llvm-dwarfdump build failures. Thank you for fixing that!

[dblaikie]

Any uses of low_pc other than the CU's low_pc that you know of that shouldn't be handled in this way? Maybe the positive list (inlined, lexical, label) should be removed?

(what about generalizing further to any address class variable? In DWARFv5 that's as easy as DW_FORM_addr and DW_FORM_addrx* forms, I think?)

llvm/lib/DWARFLinker/DWARFLinker.cpp

if (Form == dwarf::DW_FORM_addrx) {
 
     // If this is an indexed address emit the debug_info address.
     Form = dwarf::DW_FORM_addr;
   } else
     Addr = *Val.getAsAddress();
 
   if (AttrSpec.Attr == dwarf::DW_AT_low_pc) {
     if (Die.getTag() == dwarf::DW_TAG_inlined_subroutine ||
-        Die.getTag() == dwarf::DW_TAG_lexical_block)
+        Die.getTag() == dwarf::DW_TAG_lexical_block ||
+        Die.getTag() == dwarf::DW_TAG_label) {
       // The low_pc of a block or inline subroutine might get
       // relocated because it happens to match the low_pc of the
       // enclosing subprogram. To prevent issues with that, always use
       // the low_pc from the input DIE if relocations have been applied.
       Addr = (Info.OrigLowPc != std::numeric_limits<uint64_t>::max()
                   ? Info.OrigLowPc
                   : Addr) +
              Info.PCOffset;
-    else if (Die.getTag() == dwarf::DW_TAG_compile_unit) {
+    } else if (Die.getTag() == dwarf::DW_TAG_compile_unit) {
       Addr = Unit.getLowPc();
       if (Addr == std::numeric_limits<uint64_t>::max())
         return 0;
     }
     Info.HasLowPc = true;
   } else if (AttrSpec.Attr == dwarf::DW_AT_high_pc) {
     if (Die.getTag() == dwarf::DW_TAG_compile_unit) {
       if (uint64_t HighPc = Unit.getHighPc())

llvm/test/tools/dsymutil/X86/label2.test

+$ cat label.c
+int main(int argc, char **argv) {
+    if (argc) {
+        goto foobar;
+    }
+    return 1;
+foobar:
+    return 0;
+}
+
+$ clang -g label.c -c -o label.o
+$ clang label.o -o label.out
+
+RUN: dsymutil -oso-prepend-path %p/../Inputs %p/../Inputs/private/tmp/label/label.out -o %t.dSYM
+RUN: dwarfdump %t.dSYM | FileCheck %s
+
+CHECK:      DW_TAG_label
+CHECK-NEXT:   DW_AT_name    ("foobar")
+CHECK-NEXT:   DW_AT_decl_file       ("/tmp/label/label.c")
+CHECK-NEXT:   DW_AT_decl_line       (6)
+CHECK-NEXT:   DW_AT_low_pc  (0x0000000100003f9d)