[llvm] [Bolt] fix a wrong relocation update issue with weak references (PR #69136)

[Rafael Auler via llvm-commits]

================
@@ -0,0 +1,34 @@
+// This test checks whether BOLT can correctly handle relocations against weak symbols.
+
+// RUN: %clang %cflags -Wl,-z,notext -shared -Wl,-q %s -o %t.so
+// RUN: llvm-bolt %t.so -o %t.so.bolt
+// RUN: llvm-nm -n %t.so.bolt > %t.out.txt
+// RUN: llvm-objdump -dj .rodata %t.so.bolt >> %t.out.txt
+// RUN: FileCheck %s --input-file=%t.out.txt
+
+# CHECK: w func_1
+# CHECK: {{0+}}[[#%x,ADDR:]] W func_2
+
+# CHECK: {{.*}} <.rodata>:
+# CHECK-NEXT: {{.*}} .word 0x00000000
+# CHECK-NEXT: {{.*}} .word 0x00000000
+# CHECK-NEXT: {{.*}} .word 0x{{[0]+}}[[#ADDR]]
----------------
rafaelauler wrote:

In a discussion, another thing Maksim pointed out is that this actually needs to be zero too, because this part is resolved by dynamic linker at runtime. I've checked and the pre-bolt binary is indeed zeroed here. Currently, BOLT makes this non-zero because we're processing dynamic relocs for aarch64, for the reasons I discussed above.

https://github.com/llvm/llvm-project/pull/69136