[llvm] r200219 - [vectorize] Initial version of respecting PGO in the vectorizer: treat

[Chandler Carruth]

On Mon, Jan 27, 2014 at 1:41 PM, Chandler Carruth <chandlerc at gmail.com>wrote:

> ---- Block Freqs ----
>>  entry = 1.0
>>   entry -> if.else = 0.375
>>   entry -> if.then = 0.625
>>  if.then = 0.625
>>   if.then -> if.end22 = 0.625
>>  if.else = 0.375
>>   if.else -> for.cond.preheader = 0.1406
>>   if.else -> if.end22 = 0.23437
>>  for.cond.preheader = 0.1406
>>   for.cond.preheader -> for.body.lr.ph = 0.08789
>>   for.cond.preheader -> for.end = 0.05273
>>  for.body.lr.ph = 0.08789                   ### Preheader in question
>>   for.body.lr.ph -> for.body = 0.08789
>>  for.body = 2.8125                          ### Loop in question
>>
>
> Oh goodness. These static frequencies don't really make any sense at all.
> But they're also not wrong at all. ARRRRG!
>

Oh my, its worse than that. I've not thought about the block frequencies
this way before, but it appears that with the current model, inlining a
function call guarded by a branch has the perplexing property of making any
blocks within the function colder relative to their function's entry block.
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