From e004317c66651a7bf8cdea7c15060c1f357c0e3e Mon Sep 17 00:00:00 2001
From: Evan Cheng <evan.cheng@apple.com>
Date: Tue, 5 Jun 2007 20:38:42 +0000
Subject: [PATCH] Do not ifcvt if either true / false path is a backedge. Not
 profitable in almost all cases.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37440 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/IfConversion.cpp | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/lib/CodeGen/IfConversion.cpp b/lib/CodeGen/IfConversion.cpp
index c0c6b383e6c..9a35d1d11e9 100644
--- a/lib/CodeGen/IfConversion.cpp
+++ b/lib/CodeGen/IfConversion.cpp
@@ -237,6 +237,9 @@ void IfConverter::StructuralAnalysis(MachineBasicBlock *BB) {
     !TII->AnalyzeBranch(*BB, BBI.TrueBB, BBI.FalseBB, BBI.BrCond);
   if (!BBI.IsAnalyzable || BBI.BrCond.size() == 0)
     return;
+  // Do not ifcvt if either path is a back edge to the entry block.
+  if (BBI.TrueBB == BB || BBI.FalseBB == BB)
+    return;
 
   StructuralAnalysis(BBI.TrueBB);
   BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()];