[PATCH] D43498: [SCEV] Extends the SCEVInitRewriter

[Serguei Katkov via Phabricator via llvm-commits]

skatkov updated this revision to Diff 135011.
skatkov added a comment.

please take a look.


https://reviews.llvm.org/D43498

Files:
  lib/Analysis/ScalarEvolution.cpp


Index: lib/Analysis/ScalarEvolution.cpp
===================================================================
--- lib/Analysis/ScalarEvolution.cpp
+++ lib/Analysis/ScalarEvolution.cpp
@@ -4086,13 +4086,22 @@
 
 namespace {
 
+/// Takes SCEV S and Loop L. For each AddRec sub-expression, use its start
+/// expression in case its Loop is L. If it is not L then
+/// if IgnoreOtherLoops is true then use AddRec itself
+/// otherwise rewrite cannot be done.
+/// If SCEV contains non-invariant unknown SCEV rewrite cannot be done.
 class SCEVInitRewriter : public SCEVRewriteVisitor<SCEVInitRewriter> {
 public:
-  static const SCEV *rewrite(const SCEV *S, const Loop *L,
-                             ScalarEvolution &SE) {
+  static const SCEV *rewrite(const SCEV *S, const Loop *L, ScalarEvolution &SE,
+                             bool IgnoreOtherLoops = false) {
     SCEVInitRewriter Rewriter(L, SE);
     const SCEV *Result = Rewriter.visit(S);
-    return Rewriter.isValid() ? Result : SE.getCouldNotCompute();
+    if (!Rewriter.isValid())
+      return SE.getCouldNotCompute();
+    return Rewriter.isSeenOtherLoops() && !IgnoreOtherLoops
+               ? SE.getCouldNotCompute()
+               : Result;
   }
 
   const SCEV *visitUnknown(const SCEVUnknown *Expr) {
@@ -4102,21 +4111,24 @@
   }
 
   const SCEV *visitAddRecExpr(const SCEVAddRecExpr *Expr) {
-    // Only allow AddRecExprs for this loop.
+    // Only re-write AddRecExprs for this loop.
     if (Expr->getLoop() == L)
       return Expr->getStart();
-    Valid = false;
+    SeenOtherLoops = true;
     return Expr;
   }
 
   bool isValid() { return Valid; }
 
+  bool isSeenOtherLoops() { return SeenOtherLoops; }
+
 private:
   explicit SCEVInitRewriter(const Loop *L, ScalarEvolution &SE)
       : SCEVRewriteVisitor(SE), L(L) {}
 
   const Loop *L;
   bool Valid = true;
+  bool SeenOtherLoops = false;
 };
 
 /// This class evaluates the compare condition by matching it against the


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