From 081379e8b44c7e092517c11e23dc9fcc60542c32 Mon Sep 17 00:00:00 2001
From: Jatin Bhateja <jatin.bhateja@gmail.com>
Date: Sun, 26 Nov 2017 15:08:41 +0000
Subject: [PATCH] [SCEV] Adding a check on outgoing branches of a terminator
 instr for SCEVBackedgeConditionFolder, NFC.

Summary:
For a given loop, getLoopLatch returns a non-null value
when a loop has only one latch block. In the modified
context adding an assertion to check that both the outgoing branches of
a terminator instruction (of latch) does not target same header.
+
few minor code reorganization.

Reviewers: jbhateja

Reviewed By: jbhateja

Subscribers: sanjoy

Differential Revision: https://reviews.llvm.org/D40460

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@318997 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Analysis/ScalarEvolution.cpp | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp
index 53e216a5dc5..faf99c0a3c9 100644
--- a/lib/Analysis/ScalarEvolution.cpp
+++ b/lib/Analysis/ScalarEvolution.cpp
@@ -4049,9 +4049,6 @@ namespace {
 
 class SCEVInitRewriter : public SCEVRewriteVisitor<SCEVInitRewriter> {
 public:
-  SCEVInitRewriter(const Loop *L, ScalarEvolution &SE)
-      : SCEVRewriteVisitor(SE), L(L) {}
-
   static const SCEV *rewrite(const SCEV *S, const Loop *L,
                              ScalarEvolution &SE) {
     SCEVInitRewriter Rewriter(L, SE);
@@ -4076,6 +4073,9 @@ public:
   bool isValid() { return Valid; }
 
 private:
+  explicit SCEVInitRewriter(const Loop *L, ScalarEvolution &SE)
+      : SCEVRewriteVisitor(SE), L(L) {}
+
   const Loop *L;
   bool Valid = true;
 };
@@ -4093,6 +4093,8 @@ public:
     if (BasicBlock *Latch = L->getLoopLatch()) {
       BranchInst *BI = dyn_cast<BranchInst>(Latch->getTerminator());
       if (BI && BI->isConditional()) {
+        assert(BI->getSuccessor(0) != BI->getSuccessor(1) &&
+               "Both outgoing branches should not target same header!");
         BECond = BI->getCondition();
         IsPosBECond = BI->getSuccessor(0) == L->getHeader();
       } else {
@@ -4160,9 +4162,6 @@ SCEVBackedgeConditionFolder::compareWithBackedgeCondition(Value *IC) {
 
 class SCEVShiftRewriter : public SCEVRewriteVisitor<SCEVShiftRewriter> {
 public:
-  SCEVShiftRewriter(const Loop *L, ScalarEvolution &SE)
-      : SCEVRewriteVisitor(SE), L(L) {}
-
   static const SCEV *rewrite(const SCEV *S, const Loop *L,
                              ScalarEvolution &SE) {
     SCEVShiftRewriter Rewriter(L, SE);
@@ -4187,6 +4186,9 @@ public:
   bool isValid() { return Valid; }
 
 private:
+  explicit SCEVShiftRewriter(const Loop *L, ScalarEvolution &SE)
+      : SCEVRewriteVisitor(SE), L(L) {}
+
   const Loop *L;
   bool Valid = true;
 };
@@ -11342,10 +11344,6 @@ namespace {
 
 class SCEVPredicateRewriter : public SCEVRewriteVisitor<SCEVPredicateRewriter> {
 public:
-  SCEVPredicateRewriter(const Loop *L, ScalarEvolution &SE,
-                        SmallPtrSetImpl<const SCEVPredicate *> *NewPreds,
-                        SCEVUnionPredicate *Pred)
-      : SCEVRewriteVisitor(SE), NewPreds(NewPreds), Pred(Pred), L(L) {}
 
   /// Rewrites \p S in the context of a loop L and the SCEV predication
   /// infrastructure.
@@ -11406,6 +11404,11 @@ public:
   }
 
 private:
+  explicit SCEVPredicateRewriter(const Loop *L, ScalarEvolution &SE,
+                        SmallPtrSetImpl<const SCEVPredicate *> *NewPreds,
+                        SCEVUnionPredicate *Pred)
+      : SCEVRewriteVisitor(SE), NewPreds(NewPreds), Pred(Pred), L(L) {}
+
   bool addOverflowAssumption(const SCEVPredicate *P) {
     if (!NewPreds) {
       // Check if we've already made this assumption.
-- 
2.11.0