Remove the optimizations that convert BRCOND and BR_CC into
unconditional branches or fallthroghes. Instcombine/SimplifyCFG
should be simplifying branches with known conditions.
This fixes some problems caused by these transformations not
updating the MachineBasicBlock CFG.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@89017 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 00136f4..06ffdd6 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -4442,14 +4442,13 @@
SDValue Chain = N->getOperand(0);
SDValue N1 = N->getOperand(1);
SDValue N2 = N->getOperand(2);
- ConstantSDNode *N1C = dyn_cast<ConstantSDNode>(N1);
- // never taken branch, fold to chain
- if (N1C && N1C->isNullValue())
- return Chain;
- // unconditional branch
- if (N1C && N1C->getAPIntValue() == 1)
- return DAG.getNode(ISD::BR, N->getDebugLoc(), MVT::Other, Chain, N2);
+ // If N is a constant we could fold this into a fallthrough or unconditional
+ // branch. However that doesn't happen very often in normal code, because
+ // Instcombine/SimplifyCFG should have handled the available opportunities.
+ // If we did this folding here, it would be necessary to update the
+ // MachineBasicBlock CFG, which is awkward.
+
// fold a brcond with a setcc condition into a BR_CC node if BR_CC is legal
// on the target.
if (N1.getOpcode() == ISD::SETCC &&
@@ -4516,22 +4515,18 @@
CondCodeSDNode *CC = cast<CondCodeSDNode>(N->getOperand(1));
SDValue CondLHS = N->getOperand(2), CondRHS = N->getOperand(3);
+ // If N is a constant we could fold this into a fallthrough or unconditional
+ // branch. However that doesn't happen very often in normal code, because
+ // Instcombine/SimplifyCFG should have handled the available opportunities.
+ // If we did this folding here, it would be necessary to update the
+ // MachineBasicBlock CFG, which is awkward.
+
// Use SimplifySetCC to simplify SETCC's.
SDValue Simp = SimplifySetCC(TLI.getSetCCResultType(CondLHS.getValueType()),
CondLHS, CondRHS, CC->get(), N->getDebugLoc(),
false);
if (Simp.getNode()) AddToWorkList(Simp.getNode());
- ConstantSDNode *SCCC = dyn_cast_or_null<ConstantSDNode>(Simp.getNode());
-
- // fold br_cc true, dest -> br dest (unconditional branch)
- if (SCCC && !SCCC->isNullValue())
- return DAG.getNode(ISD::BR, N->getDebugLoc(), MVT::Other,
- N->getOperand(0), N->getOperand(4));
- // fold br_cc false, dest -> unconditional fall through
- if (SCCC && SCCC->isNullValue())
- return N->getOperand(0);
-
// fold to a simpler setcc
if (Simp.getNode() && Simp.getOpcode() == ISD::SETCC)
return DAG.getNode(ISD::BR_CC, N->getDebugLoc(), MVT::Other,