[cfe-dev] asm directive: symbolic label syntax

[Alexander von Below via cfe-dev]

Thanks a lot for your answer, and yes, I do: 

Working code (using numeric label): https://github.com/below/HelloSilicon/blob/main/Chapter%2009/uppertst4.c
Non-working (original) code: https://github.com/below/HelloSilicon/blob/4c4b2911c43644adfd3b78aee093857444f28472/Chapter%209/uppertst4.c

Compile using the makefile in the same folder, or using "clang -o uppertst4 uppertst4.c“

On godbolt, running the original code through  armv8-a-clang 11.0.1 or trunk, everything seems to work fine. There is an unrelated warning, but no errors. The output shows both the loop and the cont labels: https://godbolt.org/z/xY5afcYdW

Compiling the code with the symbolic cont label on an M1 using clang-1300.0.29.3 produces the errors:

uppertst4.c:22:4: error: conditional branch requires assembler-local label. 'cont' is external.
                "BGT    cont\n"
                 ^
<inline asm>:4:1: note: instantiated into assembly here
BGT     cont
^
uppertst4.c:24:4: error: conditional branch requires assembler-local label. 'cont' is external.
                "BLT    cont\n"
                 ^
<inline asm>:6:1: note: instantiated into assembly here
BLT     cont
^
uppertst4.c:28:4: error: conditional branch requires assembler-local label. 'loop' is external.
                "B.NE   loop\n"
                 ^
<inline asm>:10:1: note: instantiated into assembly here
B.NE    loop
^

Notably, now for both loop and cont, while it is sufficient to replace cont with a numeric label.

I would be glad to find out if I am doing it wrong, or if this is an issue in clang. And now my curiosity is raised why godbolt appears to differ from clang on macOS …

Thanks again

Alex


> Am 11.10.2021 um 00:26 schrieb Joerg Sonnenberger via cfe-dev <cfe-dev at lists.llvm.org>:
> 
> On Sun, Oct 10, 2021 at 12:27:28PM +0200, Alexander von Below via cfe-dev wrote:
>> I have tried to adapt gnu as code for Apple Silicon, and I have found
>> explanations for most differences. There is one issue I still have:
> 
> Do you actually have a complete self-contained example? Try godbolt.org.
> 
> Joerg
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