[AVR] Add 16-bit STS instruction

Author: Dylan McKay

lib/Target/AVR/AVRInstrInfo.td

@@ -87,6 +87,7 @@ def imm0_63_neg : PatLeaf<(imm),
 }], imm16_neg_XFORM>;
 
 def uimm6 : PatLeaf<(imm), [{ return isUInt<6>(N->getZExtValue()); }]>;
+def uimm7 : PatLeaf<(imm), [{ return isUInt<7>(N->getZExtValue()); }]>;
 
 def ioaddr_XFORM : SDNodeXForm<imm,
 [{
@@ -1275,6 +1276,17 @@ def STSKRr : F32DM<0b1,
                    [(store i8:$rd, imm:$k)]>,
              Requires<[HasSRAM]>;
 
+// Indirect store from register to data space.
+// FIXME:
+// - make this a physical instruction (not a pseudo)
+// - map r0..r15 onto r16..r31 so that the numbers match up.
+// - do weird MSB inversion as specified in datsheet
+def STS16KRr : Pseudo<(outs),
+                      (ins uimm7:$k, GPR8hi:$rd),
+                      "sts\t$k, $rd",
+                      [store i8:$rd, imm:$k]>,
+               Requires<[HasTinyEncoding]>;
+
 // STSW K+1:K, Rr+1:Rr
 //
 // Expands to:

lib/Target/AVR/AVRRegisterInfo.td

@@ -130,6 +130,13 @@ def GPR8lo : RegisterClass<"AVR", [i8], 8,
     add R15, R14, R13, R12, R11, R10, R9, R8, R7, R6, R5, R4, R3, R2, R0, R1
   )>;
 
+// Upper registers r0..r15
+def GPR8hi : RegisterClass<"AVR", [i8], 8,
+  (
+    add R16, R17, R18, R19, R20, R21, R22, R23,
+        R24, R25, R26, R27, R28, R29, R30, R31
+  )>;
+
 // 8-bit register class for instructions which take immediates.
 def LD8 : RegisterClass<"AVR", [i8], 8,
   (