From 16254567862f4d9292df48c691f86bfa57a231ed Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Tue, 2 Mar 2010 01:59:21 +0000
Subject: [PATCH] Non-affine post-inc SCEV expansions have more code which must
 be emitted after the increment. Make sure the insert position reflects this.
 This fixes PR6453.

llvm-svn: 97537
---
 lib/Analysis/ScalarEvolutionExpander.cpp      |  2 +-
 lib/Transforms/Scalar/LoopStrengthReduce.cpp  |  8 +++-
 .../LoopStrengthReduce/nonlinear-postinc.ll   | 44 +++++++++++++++++++
 3 files changed, 51 insertions(+), 3 deletions(-)
 create mode 100644 test/Transforms/LoopStrengthReduce/nonlinear-postinc.ll

diff --git a/lib/Analysis/ScalarEvolutionExpander.cpp b/lib/Analysis/ScalarEvolutionExpander.cpp
index 9aa8bfbdb17..b6c7ce64481 100644
--- a/lib/Analysis/ScalarEvolutionExpander.cpp
+++ b/lib/Analysis/ScalarEvolutionExpander.cpp
@@ -1087,7 +1087,7 @@ Value *SCEVExpander::expand(const SCEV *S) {
       // If the SCEV is computable at this level, insert it into the header
       // after the PHIs (and after any other instructions that we've inserted
       // there) so that it is guaranteed to dominate any user inside the loop.
-      if (L && S->hasComputableLoopEvolution(L))
+      if (L && S->hasComputableLoopEvolution(L) && L != PostIncLoop)
         InsertPt = L->getHeader()->getFirstNonPHI();
       while (isInsertedInstruction(InsertPt))
         InsertPt = llvm::next(BasicBlock::iterator(InsertPt));
diff --git a/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
index 8bbf19345ab..14274296de7 100644
--- a/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -2793,8 +2793,12 @@ Value *LSRInstance::Expand(const LSRFixup &LF,
     if (Instruction *I =
           dyn_cast<Instruction>(cast<ICmpInst>(LF.UserInst)->getOperand(1)))
       Inputs.push_back(I);
-  if (LF.PostIncLoop && !L->contains(LF.UserInst))
-    Inputs.push_back(L->getLoopLatch()->getTerminator());
+  if (LF.PostIncLoop) {
+    if (!L->contains(LF.UserInst))
+      Inputs.push_back(L->getLoopLatch()->getTerminator());
+    else
+      Inputs.push_back(IVIncInsertPos);
+  }
 
   // Then, climb up the immediate dominator tree as far as we can go while
   // still being dominated by the input positions.
diff --git a/test/Transforms/LoopStrengthReduce/nonlinear-postinc.ll b/test/Transforms/LoopStrengthReduce/nonlinear-postinc.ll
new file mode 100644
index 00000000000..1e63770553d
--- /dev/null
+++ b/test/Transforms/LoopStrengthReduce/nonlinear-postinc.ll
@@ -0,0 +1,44 @@
+; RUN: opt < %s -loop-reduce
+; PR6453
+
+target datalayout = "e-p:64:64:64"
+
+define void @_ZNK15PolynomialSpaceILi3EE13compute_indexEjRA3_j() nounwind {
+entry:
+  br label %bb6
+
+bb6:
+  %t4 = phi i32 [ 0, %entry ], [ %t3, %bb5 ]
+  %t16 = sub i32 undef, %t4
+  %t25 = sub i32 undef, %t4
+  %t26 = add i32 undef, %t25
+  br label %bb4
+
+bb4:
+  %t2 = phi i32 [ %t1, %bb3 ], [ 0, %bb6 ]
+  %t17 = mul i32 %t2, %t16
+  %t18 = zext i32 %t2 to i33
+  %t19 = add i32 %t2, -1
+  %t20 = zext i32 %t19 to i33
+  %t21 = mul i33 %t18, %t20
+  %t22 = lshr i33 %t21, 1
+  %t23 = trunc i33 %t22 to i32
+  %t24 = sub i32 %t17, %t23
+  %t27 = add i32 %t24, %t26
+  br i1 false, label %bb1, label %bb5
+
+bb1:
+  %t = icmp ugt i32 %t27, undef
+  br i1 %t, label %bb2, label %bb3
+
+bb3:
+  %t1 = add i32 %t2, 1
+  br label %bb4
+
+bb5:
+  %t3 = add i32 %t4, 1
+  br label %bb6
+
+bb2:
+  ret void
+}