[llvm] r182991 - X86: change MOV64ri64i32 into MOV32ri64

[Douglas Gregor]

On May 31, 2013, at 5:14 AM, Tim Northover <t.p.northover at gmail.com> wrote:

>> X86: change MOV64ri64i32 into MOV32ri64
> 
> Hmm, it seems this broke the gdb 7.5 bot:
> http://lab.llvm.org:8011/builders/clang-x86_64-ubuntu-gdb-75/builds/5399.
> 
> It looks like the test itself is dodgy: it consists of a few inline
> asm blocks, marked to clobber %eax and so on. However, it expects the
> compiler won't use those registers in *between* either.

This seems like a really nice invariant.

> Previously
> this was true, but now on -O0 instead of:
>    movl $data, %r9d
> we produce:
>    movl $data, %eax
>    movl %eax, %r9d
> 
> The extra instruction goes away (as it should) at higher
> optimisations, and I think it's perfectly valid, but the test doesn't
> like it.
> 
> Can we XFAIL individual tests on this gdb7.5 bot, or do we usually do
> something else? I can't believe this hasn't come up before.


We probably can, is the invariant this change breaks something that we want to break?

	- Doug
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