Sort the incoming values in PHI nodes to match the predecessor order.
This helps expose duplicate PHIs, which will make it easier for them
to be eliminated.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@85623 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 0ca3114..e1741a0 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -10980,6 +10980,25 @@
}
}
}
+
+ // Sort the PHI node operands to match the pred iterator order. This will
+ // help identical PHIs be eliminated by other passes. Other passes shouldn't
+ // depend on this for correctness however.
+ unsigned i = 0;
+ for (pred_iterator PI = pred_begin(PN.getParent()),
+ PE = pred_end(PN.getParent()); PI != PE; ++PI, ++i)
+ if (PN.getIncomingBlock(i) != *PI) {
+ unsigned j = PN.getBasicBlockIndex(*PI);
+ Value *VA = PN.getIncomingValue(i);
+ BasicBlock *BBA = PN.getIncomingBlock(i);
+ Value *VB = PN.getIncomingValue(j);
+ BasicBlock *BBB = PN.getIncomingBlock(j);
+ PN.setIncomingBlock(i, BBB);
+ PN.setIncomingValue(i, VB);
+ PN.setIncomingBlock(j, BBA);
+ PN.setIncomingValue(j, VA);
+ }
+
return 0;
}