[PATCH] D47087: [ScopHelper] Cache ScopExpander results.

[Eli Friedman via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rL335783: [ScopHelper] Cache ScopExpander results. (authored by efriedma, committed by ).
Herald added a reviewer: bollu.

Changed prior to commit:
  https://reviews.llvm.org/D47087?vs=147585&id=153167#toc

Repository:
  rL LLVM

https://reviews.llvm.org/D47087

Files:
  polly/trunk/lib/Support/ScopHelper.cpp


Index: polly/trunk/lib/Support/ScopHelper.cpp
===================================================================
--- polly/trunk/lib/Support/ScopHelper.cpp
+++ polly/trunk/lib/Support/ScopHelper.cpp
@@ -249,13 +249,25 @@
     return Expander.expandCodeFor(E, Ty, I);
   }
 
+  const SCEV *visit(const SCEV *E) {
+    // Cache the expansion results for intermediate SCEV expressions. A SCEV
+    // expression can refer to an operand multiple times (e.g. "x*x), so
+    // a naive visitor takes exponential time.
+    if (SCEVCache.count(E))
+      return SCEVCache[E];
+    const SCEV *Result = SCEVVisitor::visit(E);
+    SCEVCache[E] = Result;
+    return Result;
+  }
+
 private:
   SCEVExpander Expander;
   ScalarEvolution &SE;
   const char *Name;
   const Region &R;
   ValueMapT *VMap;
   BasicBlock *RTCBB;
+  DenseMap<const SCEV *, const SCEV *> SCEVCache;
 
   const SCEV *visitGenericInst(const SCEVUnknown *E, Instruction *Inst,
                                Instruction *IP) {


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