[llvm-commits] CVS: llvm/lib/Transforms/Scalar/TailDuplication.cpp

[Chris Lattner]

Changes in directory llvm/lib/Transforms/Scalar:

TailDuplication.cpp updated: 1.31 -> 1.32
---
Log message:

Allow tail duplication in more cases, relaxing the previous restriction a
bit.  This fixes Regression/Transforms/TailDup/MergeTest.ll


---
Diffs of the changes:  (+12 -1)

 TailDuplication.cpp |   13 ++++++++++++-
 1 files changed, 12 insertions(+), 1 deletion(-)


Index: llvm/lib/Transforms/Scalar/TailDuplication.cpp
diff -u llvm/lib/Transforms/Scalar/TailDuplication.cpp:1.31 llvm/lib/Transforms/Scalar/TailDuplication.cpp:1.32
--- llvm/lib/Transforms/Scalar/TailDuplication.cpp:1.31	Thu Sep  7 16:30:15 2006
+++ llvm/lib/Transforms/Scalar/TailDuplication.cpp	Sun Sep 10 13:17:58 2006
@@ -144,7 +144,18 @@
     // if (b)
     //   foo();
     // Cloning the 'if b' block into the end of the first foo block is messy.
-    return false;
+    
+    // The messy case is when the fall-through block falls through to other
+    // blocks.  This is what we would be preventing if we cloned the block.
+    DestI = Dest;
+    if (++DestI != Dest->getParent()->end()) {
+      BasicBlock *DestSucc = DestI;
+      // If any of Dest's successors are fall-throughs, don't do this xform.
+      for (succ_iterator SI = succ_begin(Dest), SE = succ_end(Dest);
+           SI != SE; ++SI)
+        if (*SI == DestSucc)
+          return false;
+    }
   }
 
   return true;