Ensure the first predecessor of a loop is the pre header.
Note that the check in ssa_phi_elimination.cc was very defensive:
it does not affect the outcome of the algorithm whether the
loop phi takes itself as the first input.
It makes things consistent to always have the pre header as first
input.
Change-Id: Ic86248c1f38af67f7432782f6deefae1f4bf1ab6
diff --git a/compiler/optimizing/nodes.cc b/compiler/optimizing/nodes.cc
index 207c605..1d7e678 100644
--- a/compiler/optimizing/nodes.cc
+++ b/compiler/optimizing/nodes.cc
@@ -194,6 +194,11 @@
}
pre_header->AddSuccessor(header);
}
+
+ // Make sure the second predecessor of a loop header is the back edge.
+ if (header->GetPredecessors().Get(1) != info->GetBackEdges().Get(0)) {
+ header->SwapPredecessors();
+ }
}
void HGraph::SimplifyCFG() {