[PATCH] VirtRegRewriter compile time reduction.

[Matthias Braun]

Hi Puyan,

LGTM with the following nitpicks fixed:

+  /// addLiveIn - Add the specified register as a live in. Note that it is

+  /// sortUniqueLiveIns - Sorts and uniques the LiveIns vector. It can be

Don't repeat the method name in the documentation comment.

+  for (auto MBBI = MF->begin(), MBBE = MF->end(); MBBI != MBBE; ++MBBI)
A range based for loop and the actual type instead of "auto" is better for readers of the code.

- Matthias


> On May 21, 2015, at 9:59 AM, Mehdi Amini <mehdi.amini at apple.com> wrote:
> 
> Hi,
> 
> Your patch does not pass clang-format (80 columns limit for example).
> It also seems to me that the loop you are adding could be a C++11 for-range loop.
> 
> — 
> Mehdi
> 
>> On May 21, 2015, at 12:54 AM, Puyan Lotfi <plotfi at apple.com> wrote:
>> 
>> Hi
>> 
>> I have a patch (attached) for reducing compile time in VirtRegRewriter
>> (especially for targets with a very high number of registers).
>> 
>> The patch changes how VirtRegRewriter::addMBBLiveIns adds registers to
>> each MachineBasicBlock's LiveIns vector by adding registers to
>> MachineBasicBlock::LiveIns without a isLiveIn check (the vector should
>> be sorted and not have duplicates), and after all registers are added
>> the LiveIns vector for each MachineBasicBlock for the current
>> MachineFunction is sorted and uniqued (a call to sortUniqueLiveIns).
>> This improves compile time by avoiding the O(LiveIns.size()) checks at
>> every addLiveIn attempt which can get expensive if MRI->getNumVirtRegs()
>> is high as this is number of iterations of the outer loop.
>> 
>> I'd like any feedback.
>> 
>> Thanks
>> 
>> PL
>> 
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