[PATCH] D94542: [X86] Default to -x86-pad-for-align=false to drop assembler difference with or w/o -g

[Fangrui Song via Phabricator via llvm-commits]

MaskRay added a comment.

In D94542#2494774 <https://reviews.llvm.org/D94542#2494774>, @reames wrote:

> Both the align and branch handling are "optimizations".  I object to one being enabled and the other disabled.  If you want them both on by default, fine.  If you want them both off by default, fine.  Having one off and one on is confusing.

I can disable the other one, too. Due to `if (!X86PadForAlign && !X86PadForBranchAlign)`, disabling one suffices.

> I also ask that a bit more background be given to justify this change.  I found the bug (https://bugs.llvm.org/show_bug.cgi?id=42138#c13), but that gives no information about the cause of the assembly difference.  Has anyone examined the cause of the labels being emitted in debug mode to see if they're necessary/useful?

I explained the cause in the description: "A -g build has more MCSymbol's and therefore may have different assembler output (e.g. a MCRelaxableFragment (jmp) may have 5 bytes with -O1 while 2 bytes with -O1 -g)."


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https://reviews.llvm.org/D94542