https://bugs.llvm.org/show_bug.cgi?id=51161
Bug ID: 51161
Summary: `-mattr` should be encoded in the IR for LTO's sake
Product: lld
Version: unspecified
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: All Bugs
Assignee: unassignedb...@nondot.org
Reporter: twd2...@gmail.com
CC: llvm-bugs@lists.llvm.org, smithp...@googlemail.com
Created attachment 25046
--> https://bugs.llvm.org/attachment.cgi?id=25046&action=edit
The diagnostic information.
When compiling the following code with LTO:
```
$ cat test.c
void _start()
{
asm volatile (
".balign 4\n\t"
"c.nop\n\t"
".balign 4\n\t"
"c.nop"
);
}
$ clang -march=rv64imac -O2 -flto -mno-relax -c test.c
$ ld.lld test.o
```
lld fails with `unable to write nop sequence of 2 bytes`.
The diagnostic information is attached.
It looks like to be due to the `HasStdExtC` check failure in
`RISCVAsmBackend::writeNopData`.
And, if I use `ld.lld -mllvm -mattr=+c test.o`, lld can generate proper machine
code.
According to Nick Desaulniers [1], `-mattr` should be encoded in the IR for
LTO's sake.
My LLVM version: commit 1b61d837b9d0 ("[Inline] Add test for PR50589 (NFC)")
[1]
https://lore.kernel.org/linux-riscv/cakwvodmnji0abyuiosfb5cld+g7ycpxk4odupa8gtfgzymx...@mail.gmail.com/
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