[clang-format] Add BreakBeforeInlineASMColon configuration

[anastasiia_lukianenko]

Summary

If `true`, colons in ASM parameters will be placed after line breaks.
true:
asm volatile("loooooooooooooooooooooooooooooooooooooooooooooong",

:
: val);

false:
asm volatile("loooooooooooooooooooooooooooooooooooooooooooooong",

: : val);

[MyDeveloperDay]

1. this needs a full context diff (diff -U 999999)
2. this needs unit tests

[anastasiia_lukianenko]

1. Diff was made by git diff with full context
2. Added description in documentation
3. Added unit test

[MyDeveloperDay]

Do you think we should show what it looks like with more complex asm examples in the tests?

what would the following look like?

asm volatile("rbit %[aVal], %[aVal]" : [aVal] "+r"(val) : "[aVal]"(val));
__asm__ __volatile__("str x0, %0" : "=m"(regs->regs[0]));
asm volatile ("get\t%0,rfsl" stringify(id) : "=d" (val))

asm ("mov %1, %0\n\t"
    "add $1, %0"
    : "=r" (dst) 
    : "r" (src));

For the "purpose of the tape" is there a reason or group of people who prefer this style? (gcc, linux kernel)

[anastasiia_lukianenko]

Nothing will happen with your examples, because the line length is less than column limit. But if I make parameters longer results will be:

BreakBeforeInlineASMColon = false;

asm volatile("rbffffit %[aVal], %[aVal]" : [aVal] "+r"(val)
             : "[aVaffffl]"(val));
__asm__ __volatile__("str fffffx0, %0"
                     : "=fffffffffffffffffffffm"(regs->regs[0]));
asm volatile("get\t%0,rffffffffsl" stringify(id)
             : "=dfffffffffffffffffffffff"(val))

BreakBeforeInlineASMColon = true;

asm volatile("rbffffit %[aVal], %[aVal]"
             : [aVal] "+r"(val)
             : "[aVaffffl]"(val));
__asm__ __volatile__("str fffffx0, %0"
                     : "=fffffffffffffffffffffm"(regs->regs[0]));
asm volatile("get\t%0,rffffffffsl" stringify(id)
             : "=dfffffffffffffffffffffff"(val))

And asking the question who will use this configuration:
We are trying to use the clang-format approach as a base for Xen [1] style formatting. During the state of testing clang-format with different configurations, we found that some points regarding the Xen coding style are not
configurable. Therefore, we decided to add them (this and other my patches [2], [3]) to be able to make a choice in different cases.

[1] - https://xenproject.org/
[2] - https://reviews.llvm.org/D92168
[3] - https://reviews.llvm.org/D91949

[MyDeveloperDay]

1. You need to default initialize BreakBeforeInlineASMColon in the LLVM style.

FormatStyle getLLVMStyle(FormatStyle::LanguageKind Language) {
       ...
       LLVMStyle.BreakBeforeInlineASMColon  = false;
       ...

2. You need a "CHECK_PARSE_BOOL" unit test

CHECK_PARSE_BOOL(BreakBeforeInlineASMColon  );

[MyDeveloperDay]

My understanding is that the following current behavour

asm("AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
    : "DEF"
    : "GHI");

asm volatile(
    "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
    : "DEF"
    : "GHI");

asm("AAAAAAAAAAAAAAAAAAA" : "DEF" : "GHI");

asm volatile("AAAAAAAAAAAAA" : "DEF" : "GHI");

asm volatile("AAAAAAAAAAAAA" : "DEF"(dst) : "GHI"(src));
asm volatile("AAAAAAAAAAAAA" : "DEF"(dst));

asm volatile("AAAAAAAAAAAAA" : [Foo] "DEF"(dst) : [Foo] "GHI"(src));
asm volatile("AAAAAAAAAAAAA" : % [Foo] "DEF"(dst) : % [Foo] "GHI"(src));

should generate as the following (with the option set to true) correct?

asm("AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
    : "DEF"
    : "GHI");

asm volatile(
    "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
    : "DEF"
    : "GHI");

asm("AAAAAAAAAAAAAAAAAAA"
    : "DEF"
    : "GHI");

asm volatile("AAAAAAAAAAAAA"
    : "DEF"
    : "GHI");

asm volatile("AAAAAAAAAAAAA"
    : "DEF"(dst)
    : "GHI"(src));

asm volatile("AAAAAAAAAAAAA"
    : "DEF"(dst));

asm volatile("AAAAAAAAAAAAA"
    : [Foo] "DEF"(dst) : [Foo] "GHI"(src));

asm volatile("AAAAAAAAAAAAA"
    : %[Foo] "DEF"(dst)
    : %[Foo] "GHI"(src));

is that correct? I highly recommend adding a few more examples in the test to show this behavior isn't just for "loooong" strings

NOTE: there is a bug in the way '%[Foo]' would get formatted to be '% [Foo]'

[anastasiia_lukianenko]

For now without my patch current behavior is the following:
Your examples listed below:

asm("AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
    : "DEF"
    : "GHI");

asm volatile(
    "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
    : "DEF"
    : "GHI");

asm("AAAAAAAAAAAAAAAAAAA" : "DEF" : "GHI");

asm volatile("AAAAAAAAAAAAA" : "DEF" : "GHI");

asm volatile("AAAAAAAAAAAAA" : "DEF"(dst) : "GHI"(src));
asm volatile("AAAAAAAAAAAAA" : "DEF"(dst));

asm volatile("AAAAAAAAAAAAA" : [Foo] "DEF"(dst) : [Foo] "GHI"(src));
asm volatile("AAAAAAAAAAAAA" : % [Foo] "DEF"(dst) : % [Foo] "GHI"(src));

Formatted with clang-format in this way:

asm("AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
    : "DEF"
    : "GHI");

asm volatile(
    "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
    : "DEF"
    : "GHI");

asm("AAAAAAAAAAAAAAAAAAA" : "DEF" : "GHI");

asm volatile("AAAAAAAAAAAAA" : "DEF" : "GHI");

asm volatile("AAAAAAAAAAAAA" : "DEF"(dst) : "GHI"(src));
asm volatile("AAAAAAAAAAAAA" : "DEF"(dst));

asm volatile("AAAAAAAAAAAAA" : [Foo] "DEF"(dst) : [Foo] "GHI"(src));
asm volatile("AAAAAAAAAAAAA" : % [Foo] "DEF"(dst) : % [Foo] "GHI"(src));

So that's why my patch is breaking only long strings. If this is a bug, I can try to fix it. Then I update my patch so the configuration will be as @MyDeveloperDay expected.

[MyDeveloperDay]

Maybe I'm confused, if you set this setting isn't it to break before ever ASM Colon is that not what is required?

[anastasiia_lukianenko]

BreakBeforeInlineASMColon configuration was created to have an option of removing this break, because without my patch it breaks before ASM colon in long lines. That's why I saved the behavior of BreakBeforeInlineASMColon=true as it was initially.
Therefore, I'm asking you is this a bug - breaking only long lines or this is normal clang-format behavior?

[MyDeveloperDay]

I think my expectation would be that if you are going to have an option BreakBeforeInlineASMColon then it should do it for all case long and short, otherwise its not going to be clear.