[PATCH] Add a shrink-wrapping pass to improve the placement of prologue and epilogue.

[Quentin Colombet]

Hi Krzysztof,

> On Apr 23, 2015, at 6:29 AM, Krzysztof Parzyszek <kparzysz at codeaurora.org> wrote:
> 
> I have a patch that does this for Hexagon.  It's implemented as a part of PEI, specifically in HexagonFrameLowering::insertPrologue.

How does the generic pass perform for you?

I would be curious to see how we can improve it.

> 
> The problem with multiple prologs is that this can increase code size, plus it's a lot harder to identify the set of registers that need to be saved in each prolog.  You don't want to be saving more registers than you need.

Indeed, and at least for now, I haven’t found cases where this is really useful. Therefore the current pass just look for one prologue and one epilogue.

Cheers,
-Quentin

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> http://reviews.llvm.org/D9210
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