[llvm] r176136 - Have a way for a target to opt-out of target-independent fast isel

[Michael Ilseman]

On Feb 27, 2013, at 11:24 AM, Eric Christopher <echristo at gmail.com> wrote:

> 
> 
> 
> On Tue, Feb 26, 2013 at 8:37 PM, Michael Ilseman <milseman at apple.com> wrote:
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> On Feb 26, 2013, at 3:30 PM, Eli Bendersky <eliben at google.com> wrote:
> 
> > Can you provide more background for this change? Is it being done for
> > the sake of debugging? What are the intended use cases?
> >
> 
> Sure! Debugging can definitely be improved by this, but this also gives targets more flexibility. Targets can fast-isel better code with more coverage in some situations. For example, SelectOperator(), even when it returns false, has side-effects and can schedule IR instructions to be fast-iselled that otherwise never would. This becomes particularly unfortunate when such instructions trigger the DAG slow-path.
> 
> 
> Is there anything that's going to be using this any time soon? Something that doesn't use the target independent fast isel path?
> 

There is an out-of-tree backend currently using it.

> -eric 

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