[PATCH] D11725: [DependenceAnalysis] Ensure All Recurrences are Affine

[Sanjoy Das via llvm-commits]

sanjoy added a comment.

I have two general questions, only tangentially related to this review (because I'm not familiar with this piece of code):

- What is the difference between `DependenceAnalysis::tryDelinearize` and `ScalarEvolution::delinearize`?
- It looks like `SCEVDivision` bails out on things other than non-affine add recs (e.g. on `SCEVUnknown`s).  Why are those okay?  IOW, is the failing assert too strong?  This is assuming that the only problem with a nested non-affine add rec is that the `SCEVDivision` aborts, are there other problems too?


================
Comment at: include/llvm/Analysis/ScalarEvolutionExpressions.h:320
@@ -319,1 +319,3 @@
 
+    /// isAffineRecursive - Return true if all SCEVAddRexExprs contained in
+    /// this expression are affine.
----------------
Nit: `SCEVAddRecExprs`

================
Comment at: lib/Analysis/DependenceAnalysis.cpp:3281
@@ -3280,2 +3280,3 @@
   const SCEVAddRecExpr *DstAR = dyn_cast<SCEVAddRecExpr>(DstSCEV);
-  if (!SrcAR || !DstAR || !SrcAR->isAffine() || !DstAR->isAffine())
+  if (!SrcAR || !DstAR || !SrcAR->isAffineRecursive() ||
+      !DstAR->isAffineRecursive())
----------------
Why not move this check to `ScalarEvolution::computeAccessFunctions`?


http://reviews.llvm.org/D11725