Don't sink argument loads into loops or other bad places. This disables folding...

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@20228 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index e5266c294f86ea0d1ceeb01811cc26a1a09e16c9..285f810bfbeb64fb3614552848583a0cb2d3420a 100644 (file)
--- a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/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::