Do not hoist instruction above branch condition. The instruction may use branch condi...

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@56286 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp
index efd17650f2da3f6c676ccba6a23b181f408cd3be..39163e40504eec1cc14b4a129116bcdee9390c59 100644 (file)
--- a/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1046,15 +1046,8 @@ static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *BB1) {
       return false;
   }
 
-  // If we get here, we can hoist the instruction. Try to place it before the
-  // icmp instruction preceeding the conditional branch.
-  BasicBlock::iterator InsertPos = BI;
-  if (InsertPos != BIParent->begin())
-    --InsertPos;
-  if (InsertPos == BrCond && !isa<PHINode>(BrCond))
-    BIParent->getInstList().splice(InsertPos, BB1->getInstList(), I);
-  else
-    BIParent->getInstList().splice(BI, BB1->getInstList(), I);
+  // If we get here, we can hoist the instruction. 
+  BIParent->getInstList().splice(BI, BB1->getInstList(), I);
 
   // Create a select whose true value is the speculatively executed value and
   // false value is the previously determined FalseV.

diff --git a/test/Transforms/SimplifyCFG/2008-09-17-SpeculativeHoist.ll b/test/Transforms/SimplifyCFG/2008-09-17-SpeculativeHoist.ll
new file mode 100644 (file)
index 0000000..b2d671d
--- /dev/null
+++ b/test/Transforms/SimplifyCFG/2008-09-17-SpeculativeHoist.ll
@@ -0,0 +1,18 @@
+; RUN: llvm-as < %s | opt -simplifycfg -disable-output
+; PR 2800
+
+define void @foo() {
+start:
+       %tmp = call i1 @bar( )          ; <i1> [#uses=4]
+       br i1 %tmp, label %brtrue, label %brfalse
+
+brtrue:                ; preds = %start
+       %tmpnew = and i1 %tmp, %tmp             ; <i1> [#uses=1]
+       br label %brfalse
+
+brfalse:               ; preds = %brtrue, %start
+       %andandtmp.0 = phi i1 [ %tmp, %start ], [ %tmpnew, %brtrue ]            ; <i1> [#uses=0]
+       ret void
+}
+
+declare i1 @bar()