[llvm] [BOLT] Account for stubs with symbols in plt (PR #192716)

[Maksim Panchenko via llvm-commits]

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+## Test that BOLT correctly handles mold-style STT_FUNC symbols in PLT
+## sections.
+
+# REQUIRES: system-linux
+
+## Build a shared library from the common stubs.
+# RUN: %clang %cflags %p/../Inputs/stub.c -fPIC -shared -o %t.so
+
+## Build and link the main binary. The linker creates a real PLT entry.
+# RUN: llvm-mc -filetype=obj -triple aarch64-linux %s -o %t.o
+# RUN: ld.lld -pie %t.o %t.so -o %t.exe --emit-relocs
+
+## Inject a mold-style STT_FUNC symbol at the PLT entry for printf.
+## Mold places "printf$plt" directly on the PLT stub; we simulate this
+## with llvm-objcopy. The PLT header is 32 bytes on AArch64, and each
+## entry is 16 bytes. printf is the only entry after the header.
+# RUN: llvm-objcopy --add-symbol "printf\$plt=.plt:32,function,local" \
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maksfb wrote:

Are mold-inserted symbols local or global?

https://github.com/llvm/llvm-project/pull/192716