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[Bug gas/6957] i386 NOPs must be derived from march not mtune


From: dsd at laptop dot org
Subject: [Bug gas/6957] i386 NOPs must be derived from march not mtune
Date: 8 Jun 2010 21:53:19 -0000

------- Additional Comments From dsd at laptop dot org  2010-06-08 21:53 -------
(In reply to comment #8)
> I agree. If it is true, assembler is broken. If you can show me
> a small testcase, I will fix it.

I can confirm the bug and I'd like to take you up on that offer, but I may have
fallen short of the *small* test case :)

I attached testcase.s which is some assembly caught from a gcc invokation inside
glibc's compile process. It's 1300 lines (sorry!) but does confirm the usage of
the nopl instruction when -mtune=i686 is passed :

$ as -Qy -o foo testcase.s
$ objdump -d foo | grep nopl
$ as -Qy -mtune=i686 -o foo testcase.s
$ objdump -d foo | grep nopl
  3d:   0f 1f 00                nopl   (%eax)

Reproduced on both:
GNU assembler version 2.19.51.0.14-37.fc12 20090722
GNU assembler version 2.20.51.0.2-17.fc14 20091009

Someone more savvy with assembly code could probably cut down my test case into
something more trivial with a small amount of effort - I'm a bit out of my
comfort zone.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
         Resolution|WORKSFORME                  |


http://sourceware.org/bugzilla/show_bug.cgi?id=6957

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