vendor/llvm/llvm-trunk-r306956

1 files changed, 9 insertions, 2 deletions

diff --git a/lib/CodeGen/TwoAddressInstructionPass.cpp b/lib/CodeGen/TwoAddressInstructionPass.cpp
index 552a89f76ca2..83c00e24d14f 100644
--- a/lib/CodeGen/TwoAddressInstructionPass.cpp
+++ b/lib/CodeGen/TwoAddressInstructionPass.cpp
@@ -68,6 +68,13 @@ EnableRescheduling("twoaddr-reschedule",
                    cl::desc("Coalesce copies by rescheduling (default=true)"),
                    cl::init(true), cl::Hidden);
 
+// Limit the number of dataflow edges to traverse when evaluating the benefit
+// of commuting operands.
+static cl::opt<unsigned> MaxDataFlowEdge(
+    "dataflow-edge-limit", cl::Hidden, cl::init(3),
+    cl::desc("Maximum number of dataflow edges to traverse when evaluating "
+             "the benefit of commuting operands"));
+
 namespace {
 class TwoAddressInstructionPass : public MachineFunctionPass {
   MachineFunction *MF;
@@ -637,10 +644,10 @@ isProfitableToCommute(unsigned regA, unsigned regB, unsigned regC,
   // To more generally minimize register copies, ideally the logic of two addr
   // instruction pass should be integrated with register allocation pass where
   // interference graph is available.
-  if (isRevCopyChain(regC, regA, 3))
+  if (isRevCopyChain(regC, regA, MaxDataFlowEdge))
     return true;
 
-  if (isRevCopyChain(regB, regA, 3))
+  if (isRevCopyChain(regB, regA, MaxDataFlowEdge))
     return false;
 
   // Since there are no intervening uses for both registers, then commute