From d9cc749318cc9ab4f36efe8a44201a72adbda2b2 Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Fri, 8 Aug 2008 18:33:12 +0000
Subject: [PATCH] Canonicalize nested AddRecs in by nesting them in order of
 loop depth.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@54545 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Analysis/ScalarEvolution.cpp | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp
index 84e02e47a0c..00a4475e28e 100644
--- a/lib/Analysis/ScalarEvolution.cpp
+++ b/lib/Analysis/ScalarEvolution.cpp
@@ -1158,6 +1158,19 @@ SCEVHandle ScalarEvolution::getAddRecExpr(std::vector<SCEVHandle> &Operands,
     return getAddRecExpr(Operands, L);             // { X,+,0 }  -->  X
   }
 
+  // Canonicalize nested AddRecs in by nesting them in order of loop depth.
+  if (SCEVAddRecExpr *NestedAR = dyn_cast<SCEVAddRecExpr>(Operands[0])) {
+    const Loop* NestedLoop = NestedAR->getLoop();
+    if (L->getLoopDepth() < NestedLoop->getLoopDepth()) {
+      std::vector<SCEVHandle> NestedOperands(NestedAR->op_begin(),
+                                             NestedAR->op_end());
+      SCEVHandle NestedARHandle(NestedAR);
+      Operands[0] = NestedAR->getStart();
+      NestedOperands[0] = getAddRecExpr(Operands, L);
+      return getAddRecExpr(NestedOperands, NestedLoop);
+    }
+  }
+
   SCEVAddRecExpr *&Result =
     (*SCEVAddRecExprs)[std::make_pair(L, std::vector<SCEV*>(Operands.begin(),
                                                             Operands.end()))];