[PATCH][FastISel] Let the target decide first if it wants to materialize a constant.

[Chad Rosier]

Juergen,
Also, I'm seeing a large number of spec2K and spec2K6 failures after this
flurry of commits.  I'm not exactly sure which one to blame, but we should
consider reverting to fix the nightlies as well as allow for proper
review.

 Chad

> So, this was in my list of things to look at but it seems like you
> went ahead and committed it without actually waiting for feedback?
>
> -eric
>
> On Tue, Aug 12, 2014 at 9:23 AM, Juergen Ributzka <juergen at apple.com>
> wrote:
>> ping :D
>>
>> On Aug 7, 2014, at 2:51 PM, Juergen Ributzka <juergen at apple.com> wrote:
>>
>>> Hi @ll,
>>>
>>> I want to change the order in which FastISel tries to materialize a
>>> constant.
>>>
>>> Originally it would try to use a simple target-independent approach,
>>> which can lead to the generation of inefficient code.
>>>
>>> On X86 this would result in the use of movabsq to materialize any 64bit
>>> integer constant - even for simple and small values such as 0 and 1.
>>> Also
>>> some very funny floating-point materialization could be observed too.
>>>
>>> On AArch64 it would materialize the constant 0 in a register even the
>>> architecture has an actual "zero" register.
>>>
>>> On ARM it would generate unnecessary mov instructions or not use mvn,
>>> etc
>>>
>>> I want to simply change the order and always asks the target first if
>>> it likes to materialize the constant. The patches a pretty simple and
>>> straight forward, but since it changes the way how FastISel works with
>>> respect to constants I wanted everyone affected by it to have at least
>>> a quick look first.
>>>
>>> Thanks
>>>
>>> Cheers,
>>> Juergen
>>>
>>> <0001-FastISel-AArch64-Cleanup-constant-materialization-co.patch><0002-FastISel-ARM-Fix-a-bug-in-the-integer-materializatio.patch><0003-FastISel-ARM-Use-MOVT-MOVW-if-the-subtarget-requests.patch><0004-FastISel-X86-Refactor-constant-materialization.-NFCI.patch><0005-FastISel-Let-the-target-decide-first-if-it-wants-to-.patch><0006-FastISel-AArch64-Make-use-of-the-zero-register-when-.patch><0007-FastISel-X86-Emit-more-efficient-instructions-for-in.patch><0008-FastISel-X86-Use-XOR-to-materialize-the-0-value.patch>
>>
>


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