From 958e292c7a71e9105df2d46ac15dcd1f3cfa0ee2 Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Fri, 19 Jun 2009 17:33:15 +0000
Subject: [PATCH] Don't (unconditionally) use getSCEVAtScope to simplify the
 step expression in IVUsers, because in the case of a use of a non-linear
 addrec outside of a loop, this causes the addrec to be evaluated as a linear
 addrec.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@73774 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Analysis/IVUsers.cpp                       |  1 -
 .../LoopStrengthReduce/quadradic-exit-value.ll | 18 ++++++++++++++++++
 2 files changed, 18 insertions(+), 1 deletion(-)
 create mode 100644 test/Transforms/LoopStrengthReduce/quadradic-exit-value.ll

diff --git a/lib/Analysis/IVUsers.cpp b/lib/Analysis/IVUsers.cpp
index 0bacc394436..6a53a83665c 100644
--- a/lib/Analysis/IVUsers.cpp
+++ b/lib/Analysis/IVUsers.cpp
@@ -112,7 +112,6 @@ static bool getSCEVStartAndStride(const SCEVHandle &SH, Loop *L, Loop *UseLoop,
   SCEVHandle AddRecStart = AddRec->getStart();
   AddRecStart = SE->getSCEVAtScope(AddRecStart, UseLoop);
   SCEVHandle AddRecStride = AddRec->getStepRecurrence(*SE);
-  AddRecStride = SE->getSCEVAtScope(AddRecStride, UseLoop);
 
   // FIXME: If Start contains an SCEVAddRecExpr from a different loop, other
   // than an outer loop of the current loop, reject it.  LSR has no concept of
diff --git a/test/Transforms/LoopStrengthReduce/quadradic-exit-value.ll b/test/Transforms/LoopStrengthReduce/quadradic-exit-value.ll
new file mode 100644
index 00000000000..d15c2dc3135
--- /dev/null
+++ b/test/Transforms/LoopStrengthReduce/quadradic-exit-value.ll
@@ -0,0 +1,18 @@
+; RUN: llvm-as < %s | opt -analyze -iv-users -disable-output | grep {Stride i64 {1,+,2}<loop>:}
+
+; The value of %r is dependent on a polynomial iteration expression.
+
+define i64 @foo(i64 %n) {
+entry:
+  br label %loop
+
+loop:
+  %indvar = phi i64 [ 0, %entry ], [ %indvar.next, %loop ]
+  %indvar.next = add i64 %indvar, 1
+  %c = icmp eq i64 %indvar.next, %n
+  br i1 %c, label %exit, label %loop
+
+exit:
+  %r = mul i64 %indvar, %indvar
+  ret i64 %r
+}