[llvm-commits] [llvm] r173331 - /llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp

[Chandler Carruth]

Author: chandlerc
Date: Thu Jan 24 02:22:40 2013
New Revision: 173331

URL: http://llvm.org/viewvc/llvm-project?rev=173331&view=rev
Log:
Lift a cheap early exit test above loops and other complex early exit
tests. No need to pay the high cost when we're never going to do
anything.

No functionality changed.

Modified:
    llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp

Modified: llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp?rev=173331&r1=173330&r2=173331&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp Thu Jan 24 02:22:40 2013
@@ -1370,6 +1370,11 @@
 ///
 /// \returns true if the conditional block is removed.
 static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *BB1) {
+  // Be conservative for now. FP select instruction can often be expensive.
+  Value *BrCond = BI->getCondition();
+  if (isa<FCmpInst>(BrCond))
+    return false;
+
   // Only speculatively execution a single instruction (not counting the
   // terminator) for now.
   Instruction *HInst = NULL;
@@ -1409,11 +1414,6 @@
     }
   }
 
-  // Be conservative for now. FP select instruction can often be expensive.
-  Value *BrCond = BI->getCondition();
-  if (isa<FCmpInst>(BrCond))
-    return false;
-
   // If BB1 is actually on the false edge of the conditional branch, remember
   // to swap the select operands later.
   bool Invert = false;