[PATCH] [SimplifyCFG] Revise common code sinking

[Liao, Michael]

The existing common code sinking in SimplifyCFG maintains a mapping from BB1 value to BB2 value pairing the phi node. This prevents case where a single value has two or more derived values in both if and else branches as, once one derived is sunk, that single value is added into that map and prevent further sinking. The added test reveal that issue. With the existing implementation, only one function call could be sunk instead of both. After the fix, both function calls are sunk. The fix changes the BB1->BB2 pairing phi map with a (BB1,BB2) -> phi map, which is more accurate to track the common code.

Yours
- Michael

-----Original Message-----
From: Manman Ren [mailto:mren at apple.com] 
Sent: Thursday, December 18, 2014 4:25 PM
To: reviews+D6688+public+a29c903f391f6bb2 at reviews.llvm.org
Cc: Liao, Michael; nrotem at apple.com; llvm-commits at cs.uiuc.edu
Subject: Re: [PATCH] [SimplifyCFG] Revise common code sinking

Hi Michael,

Can you explain what is fixed here? For the given testing case in the patch, what do we generate before and after the patch.

Thanks,
Manman

> On Dec 16, 2014, at 12:04 PM, Michael Liao <michael.liao at intel.com> wrote:
> 
> Hi Nadav & Manman
> 
> Could you help me reviewing the fix of common code sinking in SimplifyCFG?
> 
> Yours
> 
> - Michael
> 
> 
> REPOSITORY
>  rL LLVM
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> http://reviews.llvm.org/D6688
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