Disable tail duplication of call instructions. The cost

metric is way off for these in general, and this works around
buggy code like that in PR1764.  we'll see if there is a big
performance impact of this.  If so, I'll revert it tomorrow.

llvm-svn: 43668

1 files changed, 5 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Scalar/TailDuplication.cpp b/llvm/lib/Transforms/Scalar/TailDuplication.cpp
index 22d8157fc08..1473caa2ea8 100644
--- a/llvm/lib/Transforms/Scalar/TailDuplication.cpp
+++ b/llvm/lib/Transforms/Scalar/TailDuplication.cpp
@@ -115,6 +115,11 @@ bool TailDup::shouldEliminateUnconditionalBranch(TerminatorInst *TI) {
 
   for (unsigned Size = 0; I != Dest->end(); ++I) {
     if (Size == Threshold) return false;  // The block is too large.
+    
+    // Don't tail duplicate call instructions.  They are very large compared to
+    // other instructions.
+    if (isa<CallInst>(I) || isa<InvokeInst>(I)) return false;
+    
     // Only count instructions that are not debugger intrinsics.
     if (!isa<DbgInfoIntrinsic>(I)) ++Size;
   }