LLVM fails for inline asm with Link Time Optimization

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1

Hi ,
I am trying to enable link time optimization for my projects. Few of them has inline assembly which works perfectly with clang/llvm but on enabling LTO I get following error

LLVM ERROR: Error parsing inline asm

:103:2 : error 0: unknown use of instruction mnemonic without a size suffix

:104:16 : error 0: invalid operand for instruction

:106:17 : error 0: unexpected token in argument list

& so on

Is this a known issue ? Any workaround for this ?

Thanks
Ashish

2

My experience is that LTO doesn't break inline assembly.

3

Thanks for response Francois . Do you have any pointers on what can be the issue here or something I can try out. I saw similar active bug in llvm database

https://llvm.org/bugs/show_bug.cgi?id=5623

Thanks
Ashish

4

If you are getting a parse error it is very likely a different bug. In
that bug the issue is that we don't parse the function bodies to find
if some inline in them defines (or uses) a given symbol.

5

Ah , I thought that there is issue while parsing inline asm in function bodies , here are some of instruction where it cribs . Can you make out something of it ?

I am going to try out -no-integrated-as option . Not sure if it will help ?

LLVM ERROR: Error parsing inline asm

1>:1:17 : error 0: unexpected token in argument list

1> mov ebx, dword ptr 16(%esp)

1> ^

1>:2:17 : error 0: unexpected token in argument list

1> mov edi, dword ptr 24(%esp)

1> ^

1>:3:17 : error 0: unexpected token in argument list

1> mov esi, dword ptr 28(%esp)

1> ^

1>:4:21 : error 0: invalid token in expression

1> movq mm1, [edi+ebx-$8]

1> ^

1>:5:12 : error 0: invalid operand for instruction

1> pxor mm0, mm0

Thanks

Ashish

6

At which stage is this failing? Can you provide an example and commands?

Looks like the information about the use of intel syntax is being
dropped along the way.

7

It is failing at link time . Examples are what I have given above. There is an compiler option -mllvm --x86-asm-syntax=intel. Is there something similar for linker which I can provide via -plugin-opt ?

8

Even when I am passing -mllvm --x86-asm-syntax=intel to clang++.exe the assembly is generated in AT&T syntax. When can this happen ?