[dsymutil] Fix parallel linker's self-recursive typedef DIE by including referred-to types into synthetic name (#166767)

**TL;DR:** See #166675 for description of the problem, the root cause,
and one solution. This patch is the "different implementation" descried
there.

This patch tries to fix the problem by recursively including the
referred-to types into the synthetic name. This way, the synthetic name
of the typedef DIE is canonicalized. See example debug prints below:

```
SyntheticTypeNameBuilder::addDIETypeName() is called for DIE at offset 0x0000004c
    SyntheticName = {H}BarInt{F}Foo<int>:()                               <- Two different names
    Assigned to type descriptor. TypeEntryPtr = 0x0000004c0x0x150020a38   <- Hence different type entries
SyntheticTypeNameBuilder::addDIETypeName() is called for DIE at offset 0x00000044
    SyntheticName = {H}BarInt{H}BarInt{F}Foo<int>:()                      <- Two different names
    Assigned to type descriptor. TypeEntryPtr = 0x000000440x0x150020a60   <- Hence different type entries
```

The advantages of this approach over
#166675 are:
1. The resulting synthetic name is more "correct" than using decl file
and line (which _can_ still collide).
1. This doesn't depend on
#166673 to be fixed.

A **hypothetical** caveat is that it would work if any of the referenced
types resolve to the same name for some reason (similar to how the two
typedefs resolved to the same name before this patch).


# Tests

```
cd ~/public_llvm/build
bin/llvm-lit -a \
    ../llvm-project/llvm/test/tools/dsymutil/typedefs-with-same-name.test \
    ../llvm-project/llvm/test/tools/dsymutil/X86/DWARFLinkerParallel/odr-fwd-declaration.test
```

Author: royitaqi

llvm/lib/DWARFLinker/Parallel/SyntheticTypeNameBuilder.cpp

@@ -377,8 +377,10 @@ Error SyntheticTypeNameBuilder::addTypeName(UnitEntryPairTy InputUnitEntryPair,
   } break;
   }
 
-  // If name for the DIE is not determined yet add referenced types to the name.
-  if (!HasLinkageName && !HasShortName && !HasDeclFileName) {
+  // If name for the DIE is not determined yet or if the DIE is a typedef, add
+  // referenced types to the name.
+  if ((!HasLinkageName && !HasShortName && !HasDeclFileName) ||
+      InputUnitEntryPair.DieEntry->getTag() == dwarf::DW_TAG_typedef) {
     if (InputUnitEntryPair.CU->find(InputUnitEntryPair.DieEntry,
                                     getODRAttributes()))
       if (Error Err = addReferencedODRDies(InputUnitEntryPair, AddParentNames,

llvm/test/tools/dsymutil/Inputs/typedefs-with-same-name.o

@@ -35,14 +35,14 @@ void foo() { Sptrptr ptr1 = 0; }
 // CHECK: DW_TAG_member
 // CHECK-NEXT: DW_AT_name{{.*}}"field"
 
-// CHECK: 0x[[TYPEDEF_PTR_S]]: DW_TAG_typedef
-// CHECK-NEXT: DW_AT_type{{.*}}{0x[[PTR_S]]} "S *"
-// CHECK-NEXT: DW_AT_name{{.*}}"Sptr"
-
 // CHECK: 0x[[TYPEDEF_PTR_PTR_S:[a-f0-9]*]]: DW_TAG_typedef
 // CHECK-NEXT: DW_AT_type{{.*}}{0x[[PTR_PTR_S]]} "Sptr *"
 // CHECK-NEXT: DW_AT_name{{.*}}"Sptrptr"
 
+// CHECK: 0x[[TYPEDEF_PTR_S]]: DW_TAG_typedef
+// CHECK-NEXT: DW_AT_type{{.*}}{0x[[PTR_S]]} "S *"
+// CHECK-NEXT: DW_AT_name{{.*}}"Sptr"
+
 // First we confirm that first compile unit properly references type.
 //
 // CHECK: DW_TAG_compile_unit

llvm/test/tools/dsymutil/X86/DWARFLinkerParallel/odr-fwd-declaration.test

@@ -0,0 +1,41 @@
+#RUN: dsymutil --linker=parallel -f -oso-prepend-path=%p/Inputs/ -y %s -o %t.dwarf
+#RUN: llvm-dwarfdump %t.dwarf | FileCheck %s
+
+# There should be two typedef DIE named "BarInt" in the resultant .dwarf file.
+# The second should refer to the first, which refer to "Foo<int>".
+# CHECK:      0x[[FIRST_BARINT_ADDR:[0-9a-f]*]]:  DW_TAG_typedef
+# CHECK-NEXT:     DW_AT_type  (0x{{([[:xdigit:]]*)}} "Foo<int>")
+# CHECK-NEXT:     DW_AT_name  ("BarInt")
+# CHECK:      0x{{([[:xdigit:]]*)}}:  DW_TAG_typedef
+# CHECK-NEXT:     DW_AT_type  (0x[[FIRST_BARINT_ADDR]] "BarInt")
+# CHECK-NEXT:     DW_AT_name  ("BarInt")
+
+# Source:
+#
+#   template <typename T> struct Foo;
+#   typedef Foo<int> BarInt;
+#   template <typename T>
+#   struct [[clang::preferred_name(BarInt)]] Foo{};
+#   int main() {
+#     BarInt barInt;
+#     return 0;
+#   }
+#
+# Compile with:
+#
+#   $ clang++ -g -O0 -c typedefs-with-same-name.cpp -o typedefs-with-same-name.o
+#
+# To generate the debug map:
+#
+#   $ clang++ typedefs-with-same-name.o -o typedefs-with-same-name
+#   $ dsymutil -dump-debug-map typedefs-with-same-name
+
+---
+triple:          'arm64-apple-darwin'
+objects:
+  - filename:        '/typedefs-with-same-name.o'
+    timestamp:       1762438746
+    type:            102
+    symbols:
+      - { sym: _main, objAddr: 0x0, binAddr: 0x100000360, size: 0x14 }
+...