canonicalize constants to the RHS of addc/adde. If nothing uses the carry out of
addc, turn it into add.
This allows us to compile:
long long test(long long A, unsigned B) {
return (A + ((long long)B << 32)) & 123;
}
into:
_test:
movl $123, %eax
andl 4(%esp), %eax
xorl %edx, %edx
ret
instead of:
_test:
xorl %edx, %edx
movl %edx, %eax
addl 4(%esp), %eax ;; add of zero
andl $123, %eax
ret
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@34909 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 79d9e79..d48f419 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -205,6 +205,8 @@
SDOperand visitTokenFactor(SDNode *N);
SDOperand visitADD(SDNode *N);
SDOperand visitSUB(SDNode *N);
+ SDOperand visitADDC(SDNode *N);
+ SDOperand visitADDE(SDNode *N);
SDOperand visitMUL(SDNode *N);
SDOperand visitSDIV(SDNode *N);
SDOperand visitUDIV(SDNode *N);
@@ -502,6 +504,8 @@
case ISD::TokenFactor: return visitTokenFactor(N);
case ISD::ADD: return visitADD(N);
case ISD::SUB: return visitSUB(N);
+ case ISD::ADDC: return visitADDC(N);
+ case ISD::ADDE: return visitADDE(N);
case ISD::MUL: return visitMUL(N);
case ISD::SDIV: return visitSDIV(N);
case ISD::UDIV: return visitUDIV(N);
@@ -740,6 +744,49 @@
return SDOperand();
}
+SDOperand DAGCombiner::visitADDC(SDNode *N) {
+ SDOperand N0 = N->getOperand(0);
+ SDOperand N1 = N->getOperand(1);
+ ConstantSDNode *N0C = dyn_cast<ConstantSDNode>(N0);
+ ConstantSDNode *N1C = dyn_cast<ConstantSDNode>(N1);
+ MVT::ValueType VT = N0.getValueType();
+
+ // If the flag result is dead, turn this into an ADD.
+ if (N->hasNUsesOfValue(0, 1))
+ return CombineTo(N, DAG.getNode(ISD::ADD, VT, N1, N0),
+ SDOperand(N, 1));
+
+ // canonicalize constant to RHS.
+ if (N0C && !N1C)
+ return DAG.getNode(ISD::ADDC, VT, N1, N0);
+
+ // fold (add x, 0) -> x + no carry out
+ //if (N1C && N1C->isNullValue())
+ // return N0;
+
+ return SDOperand();
+}
+
+SDOperand DAGCombiner::visitADDE(SDNode *N) {
+ SDOperand N0 = N->getOperand(0);
+ SDOperand N1 = N->getOperand(1);
+ ConstantSDNode *N0C = dyn_cast<ConstantSDNode>(N0);
+ ConstantSDNode *N1C = dyn_cast<ConstantSDNode>(N1);
+ MVT::ValueType VT = N0.getValueType();
+
+ // canonicalize constant to RHS
+ if (N0C && !N1C)
+ return DAG.getNode(ISD::ADDE, VT, N1, N0, N->getOperand(2));
+
+ // fold (add x, 0) -> x
+ //if (N1C && N1C->isNullValue())
+ // return N0;
+
+ return SDOperand();
+}
+
+
+
SDOperand DAGCombiner::visitSUB(SDNode *N) {
SDOperand N0 = N->getOperand(0);
SDOperand N1 = N->getOperand(1);