[Bug gas/27075] [MIPS] Gas adds useless delay-slot nops to r6 compact branches, which have no delay slots

[positron at gnu dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=27075

--- Comment #1 from Luca Saiu <positron at gnu dot org> ---
On 2020-12-15 at 18:03 +0100, Luca Saiu wrote:

> This, while not technically assembling incorrect code, does not make
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

One more remark: I was not able to reproduce this behaviour with compact
branches, but it is possible that in some cases Gas' rewrite machinery
might actually move a previous instruction past the branch instead of
inserting a nop.  That would in fact be incorrect code with compact
branches.

For example (using a traditional MIPS branch with delay slot) this:

        addu  $10, $11, $12
        beq   $13, $14, foo

may turn into:

   0:   11aeffff        beq     $13,$14,0x0
   4:   016c5021        addu    $10,$11,$12

If that happened with compact branches it would be a disaster.

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