From 0c56a548edd6f1270040b71ec366a1b328f13df5 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Thu, 17 Feb 2005 19:40:32 +0000
Subject: Don't sink argument loads into loops or other bad places.  This
 disables folding of argument loads with instructions that are not in the
 entry block.

llvm-svn: 20228
---
 llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

(limited to 'llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp')

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index e5266c294f8..285f810bfbe 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -852,7 +852,14 @@ static BasicBlock *IsOnlyUsedInOneBasicBlock(Argument *A) {
        ++UI)
     if (isa<PHINode>(*UI) || cast<Instruction>(*UI)->getParent() != BB)
       return 0;  // Disagreement among the users?
-  return BB;
+
+  // Okay, there is a single BB user.  Only permit this optimization if this is
+  // the entry block, otherwise, we might sink argument loads into loops and
+  // stuff.  Later, when we have global instruction selection, this won't be an
+  // issue clearly.
+  if (BB == BB->getParent()->begin())
+    return BB;
+  return 0;
 }
 
 void SelectionDAGISel::
-- 
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