[PATCH] Loop Vectorizer doesn't use %zmm registers on targets supporting AVX512.

[zinovy.nis at gmail.com]

I have no real avx512 architecture at hands.
But I believe that using wider vectors is better than using shorter ones in 
this case.
BTW, the KNL cost model in LLVM was taken from the Haswell cost model (see 
TODOs in x86.td), so it can't be very accurate for KNL.

-----Исходное сообщение----- 
From: Arnold Schwaighofer
Sent: Friday, March 14, 2014 8:08 PM
To: elena.demikhovsky at intel.com ; rob.khasanov at gmail.com ; 
avolkov.intel at gmail.com ; nrotem at apple.com ; zinovy.nis at gmail.com
Cc: llvm-commits at cs.uiuc.edu ; Andrea_DiBiagio at sn.scee.net ; 
aschwaighofer at apple.com
Subject: Re: [PATCH] Loop Vectorizer doesn't use %zmm registers on targets 
supporting AVX512.


  Curious, did you test whether the cost model works reasonably well across 
the test-suite with this turned on? Are there any/many major regressions 
with this patch applied vs without on an avx512 architecture?


  Thanks,
  Arnold


================
Comment at: test/CodeGen/X86/avx512-vectorizer.ll:8
@@ +7,3 @@
+
+define void @foo(float* noalias nocapture readonly %a, float* noalias 
nocapture readonly %b, float* noalias nocapture %c, i32 %n) #0 {
+entry:
----------------
You could remove the no capture and readonly attributes. They are not needed 
for this test case.

I am also surprised that llvm accepts dangling function attributes ("#0”) 
but it does :).


http://llvm-reviews.chandlerc.com/D3078