[llvm-commits] [llvm] r60210 - in /llvm/trunk: lib/Transforms/Scalar/CodeGenPrepare.cpp lib/Transforms/Scalar/JumpThreading.cpp test/Transforms/JumpThreading/2008-11-28-InfLoop.ll

[Chris Lattner]

Author: lattner
Date: Fri Nov 28 13:54:49 2008
New Revision: 60210

URL: http://llvm.org/viewvc/llvm-project?rev=60210&view=rev
Log:
don't call MergeBasicBlockIntoOnlyPred on a block whose only
predecessor is itself.  This doesn't make sense, and this is
a dead infinite loop anyway.


Added:
    llvm/trunk/test/Transforms/JumpThreading/2008-11-28-InfLoop.ll
Modified:
    llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp
    llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp

Modified: llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp?rev=60210&r1=60209&r2=60210&view=diff

==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp Fri Nov 28 13:54:49 2008
@@ -205,16 +205,18 @@
   // If the destination block has a single pred, then this is a trivial edge,
   // just collapse it.
   if (BasicBlock *SinglePred = DestBB->getSinglePredecessor()) {
-    // Remember if SinglePred was the entry block of the function.  If so, we
-    // will need to move BB back to the entry position.
-    bool isEntry = SinglePred == &SinglePred->getParent()->getEntryBlock();
-    MergeBasicBlockIntoOnlyPred(DestBB);
+    if (SinglePred != DestBB) {
+      // Remember if SinglePred was the entry block of the function.  If so, we
+      // will need to move BB back to the entry position.
+      bool isEntry = SinglePred == &SinglePred->getParent()->getEntryBlock();
+      MergeBasicBlockIntoOnlyPred(DestBB);
 
-    if (isEntry && BB != &BB->getParent()->getEntryBlock())
-      BB->moveBefore(&BB->getParent()->getEntryBlock());
-    
-    DOUT << "AFTER:\n" << *DestBB << "\n\n\n";
-    return;
+      if (isEntry && BB != &BB->getParent()->getEntryBlock())
+        BB->moveBefore(&BB->getParent()->getEntryBlock());
+      
+      DOUT << "AFTER:\n" << *DestBB << "\n\n\n";
+      return;
+    }
   }
 
   // Otherwise, we have multiple predecessors of BB.  Update the PHIs in DestBB

Modified: llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp?rev=60210&r1=60209&r2=60210&view=diff

==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp Fri Nov 28 13:54:49 2008
@@ -164,7 +164,8 @@
   // because now the condition in this block can be threaded through
   // predecessors of our predecessor block.
   if (BasicBlock *SinglePred = BB->getSinglePredecessor())
-    if (SinglePred->getTerminator()->getNumSuccessors() == 1) {
+    if (SinglePred->getTerminator()->getNumSuccessors() == 1 &&
+        SinglePred != BB) {
       // Remember if SinglePred was the entry block of the function.  If so, we
       // will need to move BB back to the entry position.
       bool isEntry = SinglePred == &SinglePred->getParent()->getEntryBlock();

Added: llvm/trunk/test/Transforms/JumpThreading/2008-11-28-InfLoop.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/JumpThreading/2008-11-28-InfLoop.ll?rev=60210&view=auto

==============================================================================
--- llvm/trunk/test/Transforms/JumpThreading/2008-11-28-InfLoop.ll (added)
+++ llvm/trunk/test/Transforms/JumpThreading/2008-11-28-InfLoop.ll Fri Nov 28 13:54:49 2008
@@ -0,0 +1,17 @@
+; RUN: llvm-as < %s | opt -jump-threading | llvm-dis
+
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
+target triple = "i386-apple-darwin9.5"
+	%struct.decContext = type { i32 }
+	%struct.decNumber = type { i32, i32 }
+
+define i32 @decNumberPower(%struct.decNumber* %res, %struct.decNumber* %lhs, %struct.decNumber* %rhs, %struct.decContext* %set) nounwind {
+entry:
+	br i1 true, label %decDivideOp.exit, label %bb7.i
+
+bb7.i:		; preds = %bb7.i, %entry
+	br label %bb7.i
+
+decDivideOp.exit:		; preds = %entry
+	ret i32 undef
+}