[PATCH] Enhance loop rotation with existence of profile data in MachineBlockPlacement pass.

[Cong Hou]

When the outer loop is rotated, the inner loop is already linked to other
CFG nodes in the outer loop. So I think we won't have to adjust the current
algorithm as we have already considered all costs the rotation may bring or
reduce.


thanks,
Cong

On Mon, Jul 6, 2015 at 9:57 AM, Xinliang David Li <xinliangli at gmail.com>
wrote:

> Does the cost analysis work well for loop nest? After the inner loop chain
> is formed and rotated, it will be later be merged into the parent loop
> chain. The cost analysis for the parent loop may need to be adjusted to
> consider the inner loops that are already rotated.
>
> David
>
> On Tue, Jun 30, 2015 at 2:29 PM, Cong Hou <congh at google.com> wrote:
>
>> Update the patch by adding two opt parameters that define the cost of
>> misfetch and jump instruction, and use them when rotating loops.
>>
>>
>> http://reviews.llvm.org/D10717
>>
>> Files:
>>   lib/CodeGen/MachineBlockPlacement.cpp
>>   test/CodeGen/X86/code_placement_loop_rotation.ll
>>
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