[PowerPC] Add the SUBFUS instruction to Future CPU.

[stefanp]

Summary

Add a new instruction called SUBUFS that does saturating subtract.
This instruction is only for Future CPU.

[amyk]

LGTM.

llvm/lib/Target/PowerPC/PPCInstrFuture.td

 //===-- PPCInstrFuture.td - Future Instruction Set --------*- tablegen -*-===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file describes the instructions introduced for the Future CPU.
 //
 //===----------------------------------------------------------------------===//
 
+class XOForm_RTAB5_L1<bits<6> opcode, bits<9> xo, dag OOL, dag IOL,
+                      string asmstr, list<dag> pattern>
+         : I<opcode, OOL, IOL, asmstr, NoItinerary> {
+  bits<5> RT;
+  bits<5> RA;
+  bits<5> RB;
+  bit L;
+
+  let Pattern = pattern;
+
+  bit RC = 0;    // set by isRecordForm
+
+  let Inst{6-10}  = RT;
+  let Inst{11-15} = RA;
+  let Inst{16-20} = RB;
+  let Inst{21}    = L;
+  let Inst{22-30} = xo;
+  let Inst{31}    = RC;
+}
+
+multiclass XOForm_RTAB5_L1r<bits<6> opcode, bits<9> xo, dag OOL, dag IOL,
+                            string asmbase, string asmstr,
+                            list<dag> pattern> {
+  let BaseName = asmbase in {
+    def NAME : XOForm_RTAB5_L1<opcode, xo, OOL, IOL,
+                               !strconcat(asmbase, !strconcat(" ", asmstr)),
+                               pattern>, RecFormRel;
+    let Defs = [CR0] in
+    def _rec : XOForm_RTAB5_L1<opcode, xo, OOL, IOL,
+                               !strconcat(asmbase, !strconcat(". ", asmstr)),
+                               []>, isRecordForm, RecFormRel;
+  }
+}
+
+let Predicates = [IsISAFuture] in {
+defm SUBFUS : XOForm_RTAB5_L1r<31, 72, (outs g8rc:$RT),
+                               (ins g8rc:$RA, g8rc:$RB, u1imm:$L),
+                               "subfus",  "$RT, $L, $RA, $RB", []>;
+}
 

llvm/test/MC/Disassembler/PowerPC/ppc-encoding-ISAFuture.txt

 #CHECK: dmsetdmrz 3
 0x7d 0x82 0x01 0x62
 
 #CHECK: dmmr 4, 5
 0x7e 0x06 0xa1 0x62
 
 #CHECK: dmxor 6, 7
 0x7f 0x07 0xe1 0x62
+
+#CHECK: subfus 3, 0, 4, 5
+0x7c 0x64 0x28 0x90
+
+#CHECK: subfus 3, 1, 4, 5
+0x7c 0x64 0x2c 0x90
+
+#CHECK: subfus. 3, 0, 4, 5
+0x7c 0x64 0x28 0x91
+
+#CHECK: subfus. 3, 1, 4, 5
+0x7c 0x64 0x2c 0x91

llvm/test/MC/Disassembler/PowerPC/ppc64le-encoding-ISAFuture.txt

 #CHECK: dmsetdmrz 3
 0x62 0x01 0x82 0x7d
 
 #CHECK: dmmr 4, 5
 0x62 0xa1 0x06 0x7e
 
 #CHECK: dmxor 6, 7
 0x62 0xe1 0x07 0x7f
+
+#CHECK: subfus 3, 0, 4, 5
+0x90 0x28 0x64 0x7c
+
+#CHECK: subfus 3, 1, 4, 5
+0x90 0x2c 0x64 0x7c
+
+#CHECK: subfus. 3, 0, 4, 5
+0x91 0x28 0x64 0x7c
+
+#CHECK: subfus. 3, 1, 4, 5
+0x91 0x2c 0x64 0x7c

llvm/test/MC/PowerPC/ppc-encoding-ISAFuture.s

 
 # CHECK-BE: dmmr 4, 5                     # encoding: [0x7e,0x06,0xa1,0x62]
 # CHECK-LE: dmmr 4, 5                     # encoding: [0x62,0xa1,0x06,0x7e]
             dmmr 4, 5
 
 # CHECK-BE: dmxor 6, 7                    # encoding: [0x7f,0x07,0xe1,0x62]
 # CHECK-LE: dmxor 6, 7                    # encoding: [0x62,0xe1,0x07,0x7f]
             dmxor 6, 7
+
+# CHECK-BE: subfus 3, 0, 4, 5          # encoding: [0x7c,0x64,0x28,0x90]
+# CHECK-LE: subfus 3, 0, 4, 5          # encoding: [0x90,0x28,0x64,0x7c]
+            subfus 3, 0, 4, 5
+
+# CHECK-BE: subfus 3, 1, 4, 5          # encoding: [0x7c,0x64,0x2c,0x90]
+# CHECK-LE: subfus 3, 1, 4, 5          # encoding: [0x90,0x2c,0x64,0x7c]
+            subfus 3, 1, 4, 5
+
+# CHECK-BE: subfus. 3, 0, 4, 5         # encoding: [0x7c,0x64,0x28,0x91]
+# CHECK-LE: subfus. 3, 0, 4, 5         # encoding: [0x91,0x28,0x64,0x7c]
+            subfus. 3, 0, 4, 5
+
+# CHECK-BE: subfus. 3, 1, 4, 5         # encoding: [0x7c,0x64,0x2c,0x91]
+# CHECK-LE: subfus. 3, 1, 4, 5         # encoding: [0x91,0x2c,0x64,0x7c]
+            subfus. 3, 1, 4, 5