[SystemZ] Extend integer absolute selection
This patch makes more use of LPGFR and LNGFR. It builds on top of
the LTGFR selection from r197234. Most of the tests are motivated
by what InstCombine would produce.
llvm-svn: 197236
diff --git a/llvm/lib/Target/SystemZ/SystemZISelLowering.cpp b/llvm/lib/Target/SystemZ/SystemZISelLowering.cpp
index e7399fe..49547d3 100644
--- a/llvm/lib/Target/SystemZ/SystemZISelLowering.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZISelLowering.cpp
@@ -1622,6 +1622,28 @@
DAG.getConstant(C.CCMask, MVT::i32), Dest, Glue);
}
+// Return true if Pos is CmpOp and Neg is the negative of CmpOp,
+// allowing Pos and Neg to be wider than CmpOp.
+static bool isAbsolute(SDValue CmpOp, SDValue Pos, SDValue Neg) {
+ return (Neg.getOpcode() == ISD::SUB &&
+ Neg.getOperand(0).getOpcode() == ISD::Constant &&
+ cast<ConstantSDNode>(Neg.getOperand(0))->getZExtValue() == 0 &&
+ Neg.getOperand(1) == Pos &&
+ (Pos == CmpOp ||
+ (Pos.getOpcode() == ISD::SIGN_EXTEND &&
+ Pos.getOperand(0) == CmpOp)));
+}
+
+// Return the absolute or negative absolute of Op; IsNegative decides which.
+static SDValue getAbsolute(SelectionDAG &DAG, SDLoc DL, SDValue Op,
+ bool IsNegative) {
+ Op = DAG.getNode(SystemZISD::IABS, DL, Op.getValueType(), Op);
+ if (IsNegative)
+ Op = DAG.getNode(ISD::SUB, DL, Op.getValueType(),
+ DAG.getConstant(0, Op.getValueType()), Op);
+ return Op;
+}
+
SDValue SystemZTargetLowering::lowerSELECT_CC(SDValue Op,
SelectionDAG &DAG) const {
SDValue CmpOp0 = Op.getOperand(0);
@@ -1632,6 +1654,21 @@
SDLoc DL(Op);
Comparison C(getCmp(DAG, CmpOp0, CmpOp1, CC));
+
+ // Check for absolute and negative-absolute selections, including those
+ // where the comparison value is sign-extended (for LPGFR and LNGFR).
+ // This check supplements the one in DAGCombiner.
+ if (C.Opcode == SystemZISD::ICMP &&
+ C.CCMask != SystemZ::CCMASK_CMP_EQ &&
+ C.CCMask != SystemZ::CCMASK_CMP_NE &&
+ C.Op1.getOpcode() == ISD::Constant &&
+ cast<ConstantSDNode>(C.Op1)->getZExtValue() == 0) {
+ if (isAbsolute(C.Op0, TrueOp, FalseOp))
+ return getAbsolute(DAG, DL, TrueOp, C.CCMask & SystemZ::CCMASK_CMP_LT);
+ if (isAbsolute(C.Op0, FalseOp, TrueOp))
+ return getAbsolute(DAG, DL, FalseOp, C.CCMask & SystemZ::CCMASK_CMP_GT);
+ }
+
SDValue Glue = emitCmp(DAG, DL, C);
// Special case for handling -1/0 results. The shifts we use here
@@ -2324,6 +2361,7 @@
OPCODE(SIBCALL);
OPCODE(PCREL_WRAPPER);
OPCODE(PCREL_OFFSET);
+ OPCODE(IABS);
OPCODE(ICMP);
OPCODE(FCMP);
OPCODE(TM);