Assembler for arm64 ignores padding value of 0 for .balign directive

[llvmbot]

Bugzilla Link	30955
Version	3.8
OS	All
Reporter	LLVM Bugzilla Contributor

Extended Description

When a specific padding value of 0 is passed to a .balign directive in an executable area, the value is ignored and NOP instructions are inserted instead.

The value is respected for the .balignw .balignl variants. Further, if a non-zero value is specified, it's respected.

Shouldn't an explicit 0 padding value be respected for .balign?

Reproducer:

// Contents of foo.S
.section TestSection, "x"
  add x14, x14, 0x1
  .balign 0x10, 0
  add x14, x14, 0x1
.end

Command line:

clang -target arm64-unknown-linux -c -o foo.o foo.S

[llvmbot]

@llvm/issue-subscribers-backend-aarch64

Author: None (llvmbot)

| | | | --- | --- | | Bugzilla Link | [30955](https://llvm.org/bz30955) | | Version | 3.8 | | OS | All | | Reporter | LLVM Bugzilla Contributor |

Extended Description

When a specific padding value of 0 is passed to a .balign directive in an executable area, the value is ignored and NOP instructions are inserted instead.

The value is respected for the .balignw .balignl variants. Further, if a non-zero value is specified, it's respected.

Shouldn't an explicit 0 padding value be respected for .balign?

Reproducer:

// Contents of foo.S
.section TestSection, "x"
add x14, x14, 0x1
.balign 0x10, 0
add x14, x14, 0x1
.end

Command line:
clang -target arm64-unknown-linux -c -o foo.o foo.S

[lenary]

Godbolt link here: https://godbolt.org/z/q11q8G3jc

This still happens, I know why, I am working on a fix.