No relocation are emitted for pointer on weak function for arm

[Ralender]

Make file with the following named tmp.c

int __attribute__((weak)) foo() { return 9; }

typedef int (*func_ptr)();

func_ptr get() { return &foo; }

run:

clang -target arm-none-linux-android tmp.c -c -o out.o
llvm-objdump -r out.o

The function pointer in get may get overridden by the foo from an other TU.
So the compiler needs to generate a relocation. but in this case it doesn't.

Maybe the problem is simply that foo is emitted with dso_local.
Note that other backends(X86, aarch64) still generate relocations even with the dso_local.

[llvmbot]

@llvm/issue-subscribers-backend-arm

Author: None (Ralender)

Make file with the following named tmp.ll ```llvm define weak dso_local arm_aapcscc i32 @foo() { ret i32 9 }

define dso_local arm_aapcscc ptr @get() {
ret ptr @foo
}

run: 
```bash
clang++ -target arm-none-linux-android tmp.ll -c -o out.o
llvm-objdump -r out.o

the function pointer in get may get overridden by the foo from an other TU. so the compiler needs to generate a relocation. but in this case it doesn't.

[llvmbot]

@llvm/issue-subscribers-bug

Author: None (Ralender)

Make file with the following named tmp.ll ```llvm define weak dso_local arm_aapcscc i32 @foo() { ret i32 9 }

define dso_local arm_aapcscc ptr @get() {
ret ptr @foo
}

run: 
```bash
clang++ -target arm-none-linux-android tmp.ll -c -o out.o
llvm-objdump -r out.o

the function pointer in get may get overridden by the foo from an other TU. so the compiler needs to generate a relocation. but in this case it doesn't.

[pratlucas]

From an initial look into the reproducer, it appears that the issue only affects the android target env. A relocation is created as expected for other target triples, such as arm-none-eabi:

$ clang --target=arm-none-eabi test.c -c -o test.o
$ llvm-objdump -r test.o                          

test.o: file format elf32-littlearm

RELOCATION RECORDS FOR [.text]:
OFFSET   TYPE                     VALUE
00000028 R_ARM_ABS32              foo

RELOCATION RECORDS FOR [.ARM.exidx]:
OFFSET   TYPE                     VALUE
00000000 R_ARM_PREL31             .text
00000008 R_ARM_PREL31             .text

https://godbolt.org/z/Mv1Tscf7s