[llvm] [Symbolize] Always use filename:line from debug info when debug info for the given address is available. (PR #128619)

[Zequan Wu via llvm-commits]

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@@ -0,0 +1,175 @@
+# Test llvm-symbolizer always uses line info from debug info if present.
+# RUN: yaml2obj %s -o %t
+# RUN: llvm-symbolizer --obj=%t 0x1 | FileCheck %s
+
+# CHECK:      foo(bool)
+# CHECK-NEXT: ??:0:0
+
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ZequanWu wrote:

I experimented a bit and think the dwarf info emitter (at least from llvm ir to object file) implicitly drops `DIGlobalVariable` if its line number is 0. Here's what I tried:
- `clang++ file.cpp -O2 -g  -nostdlib -emit-llvm -S -o file.ll` and then modify the line number in `DIGlobalVariable` to 0.  
- `clang++ file.ll -fuse-ld=lld -g  -shared -nostdlib -c -o file.o` to get object file.
- Using `llvm-dwarfdump --debug-info file.o` to examine the debug info location for the global variable. It's only able to show the source location for the global variable when the line in `DIGlobalVariable` is not 0.

So, I *think* the change in `symbolizeData` is unnecessary as clang toolchain doesn't produce this case (I might be wrong, it might be possible in some cases).

https://github.com/llvm/llvm-project/pull/128619