[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.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@197236 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 55 insertions, 4 deletions

diff --git a/lib/Target/SystemZ/SystemZISelLowering.cpp b/lib/Target/SystemZ/SystemZISelLowering.cpp
index e7399fe6f0..49547d319e 100644
--- a/lib/Target/SystemZ/SystemZISelLowering.cpp
+++ b/lib/Target/SystemZ/SystemZISelLowering.cpp
@@ -1622,6 +1622,28 @@ SDValue SystemZTargetLowering::lowerBR_CC(SDValue Op, SelectionDAG &DAG) const {
                      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 @@ SDValue SystemZTargetLowering::lowerSELECT_CC(SDValue Op,
   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 @@ const char *SystemZTargetLowering::getTargetNodeName(unsigned Opcode) const {
     OPCODE(SIBCALL);
     OPCODE(PCREL_WRAPPER);
     OPCODE(PCREL_OFFSET);
+    OPCODE(IABS);
     OPCODE(ICMP);
     OPCODE(FCMP);
     OPCODE(TM);
diff --git a/lib/Target/SystemZ/SystemZISelLowering.h b/lib/Target/SystemZ/SystemZISelLowering.h
index 4cbb30da8b..01f09c3737 100644
--- a/lib/Target/SystemZ/SystemZISelLowering.h
+++ b/lib/Target/SystemZ/SystemZISelLowering.h
@@ -45,6 +45,9 @@ namespace SystemZISD {
     // as a register base.
     PCREL_OFFSET,
 
+    // Integer absolute.
+    IABS,
+
     // Integer comparisons.  There are three operands: the two values
     // to compare, and an integer of type SystemZICMP.
     ICMP,
diff --git a/lib/Target/SystemZ/SystemZInstrInfo.td b/lib/Target/SystemZ/SystemZInstrInfo.td
index 00cb7d2c36..587b170b5a 100644
--- a/lib/Target/SystemZ/SystemZInstrInfo.td
+++ b/lib/Target/SystemZ/SystemZInstrInfo.td
@@ -595,22 +595,28 @@ let neverHasSideEffects = 1, isAsCheapAsAMove = 1, isMoveImm = 1,
 
 let Defs = [CC] in {
   let CCValues = 0xF, CompareZeroCCMask = 0x8 in {
-    def LPR  : UnaryRR <"lp",  0x10,   z_iabs32, GR32, GR32>;
-    def LPGR : UnaryRRE<"lpg", 0xB900, z_iabs64, GR64, GR64>;
+    def LPR  : UnaryRR <"lp",  0x10,   z_iabs, GR32, GR32>;
+    def LPGR : UnaryRRE<"lpg", 0xB900, z_iabs, GR64, GR64>;
   }
   let CCValues = 0xE, CompareZeroCCMask = 0xE in
     def LPGFR : UnaryRRE<"lpgf", 0xB910, null_frag, GR64, GR32>;
 }
+def : Pat<(z_iabs32 GR32:$src), (LPR  GR32:$src)>;
+def : Pat<(z_iabs64 GR64:$src), (LPGR GR64:$src)>;
+defm : SXU<z_iabs,   LPGFR>;
 defm : SXU<z_iabs64, LPGFR>;
 
 let Defs = [CC] in {
   let CCValues = 0xF, CompareZeroCCMask = 0x8 in {
-    def LNR  : UnaryRR <"ln",  0x11,   z_inegabs32, GR32, GR32>;
-    def LNGR : UnaryRRE<"lng", 0xB901, z_inegabs64, GR64, GR64>;
+    def LNR  : UnaryRR <"ln",  0x11,   z_inegabs, GR32, GR32>;
+    def LNGR : UnaryRRE<"lng", 0xB901, z_inegabs, GR64, GR64>;
   }
   let CCValues = 0xE, CompareZeroCCMask = 0xE in
     def LNGFR : UnaryRRE<"lngf", 0xB911, null_frag, GR64, GR32>;
 }
+def : Pat<(z_inegabs32 GR32:$src), (LNR  GR32:$src)>;
+def : Pat<(z_inegabs64 GR64:$src), (LNGR GR64:$src)>;
+defm : SXU<z_inegabs,   LNGFR>;
 defm : SXU<z_inegabs64, LNGFR>;
 
 let Defs = [CC] in {
diff --git a/lib/Target/SystemZ/SystemZOperators.td b/lib/Target/SystemZ/SystemZOperators.td
index 771fbc32f3..bffe1a5618 100644
--- a/lib/Target/SystemZ/SystemZOperators.td
+++ b/lib/Target/SystemZ/SystemZOperators.td
@@ -103,6 +103,7 @@ def z_sibcall           : SDNode<"SystemZISD::SIBCALL", SDT_ZCall,
 def z_pcrel_wrapper     : SDNode<"SystemZISD::PCREL_WRAPPER", SDT_ZWrapPtr, []>;
 def z_pcrel_offset      : SDNode<"SystemZISD::PCREL_OFFSET",
                                  SDT_ZWrapOffset, []>;
+def z_iabs              : SDNode<"SystemZISD::IABS", SDTIntUnaryOp, []>;
 def z_icmp              : SDNode<"SystemZISD::ICMP", SDT_ZICmp, [SDNPOutGlue]>;
 def z_fcmp              : SDNode<"SystemZISD::FCMP", SDT_ZCmp, [SDNPOutGlue]>;
 def z_tm                : SDNode<"SystemZISD::TM", SDT_ZICmp, [SDNPOutGlue]>;
@@ -349,6 +350,9 @@ def or_as_revinserti8 : PatFrag<(ops node:$src1, node:$src2),
                                    APInt::getLowBitsSet(BitWidth, 8));
 }]>;
 
+// Negative integer absolute.
+def z_inegabs : PatFrag<(ops node:$src), (ineg (z_iabs node:$src))>;
+
 // Integer absolute, matching the canonical form generated by DAGCombiner.
 def z_iabs32 : PatFrag<(ops node:$src),
                        (xor (add node:$src, (sra node:$src, (i32 31))),