[Sparc] Replace CMP instructions with InstAlias (NFCI)

llvm/lib/Target/Sparc/SparcISelLowering.cpp

@@ -3642,3 +3642,11 @@ void SparcTargetLowering::insertSSPDeclarations(Module &M) const {
   if (!Subtarget->isTargetLinux())
     return TargetLowering::insertSSPDeclarations(M);
 }
+
+void SparcTargetLowering::AdjustInstrPostInstrSelection(MachineInstr &MI,
+                                                        SDNode *Node) const {
+  assert(MI.getOpcode() == SP::SUBCCrr || MI.getOpcode() == SP::SUBCCri);
+  // If the result is dead, replace it with %g0.
+  if (!Node->hasAnyUseOfValue(0))
+    MI.getOperand(0).setReg(SP::G0);
+}

llvm/lib/Target/Sparc/SparcISelLowering.h

@@ -222,7 +222,10 @@ namespace llvm {
 
     MachineBasicBlock *expandSelectCC(MachineInstr &MI, MachineBasicBlock *BB,
                                       unsigned BROpcode) const;
+
+    void AdjustInstrPostInstrSelection(MachineInstr &MI,
+                                       SDNode *Node) const override;
   };
 } // end namespace llvm
 
-#endif    // SPARC_ISELLOWERING_H
+#endif // LLVM_LIB_TARGET_SPARC_SPARCISELLOWERING_H

llvm/lib/Target/Sparc/SparcInstr64Bit.td

@@ -65,6 +65,7 @@ def : Pat<(i64 0), (COPY (i64 G0))>,
   Requires<[Is64Bit]>;
 
 // The ALU instructions want their simm13 operands as i32 immediates.
+// FIXME: This is no longer true, they are now pointer-sized.
 def as_i32imm : SDNodeXForm<imm, [{
   return CurDAG->getTargetConstant(N->getSExtValue(), SDLoc(N), MVT::i32);
 }]>;
@@ -173,8 +174,8 @@ def TLS_ADDXrr : F3_1<2, 0b000000, (outs I64Regs:$rd),
                        (tlsadd i64:$rs1, i64:$rs2, tglobaltlsaddr:$sym))]>;
 }
 
-def : Pat<(SPcmpicc i64:$a, i64:$b), (CMPrr $a, $b)>;
-def : Pat<(SPcmpicc i64:$a, (i64 simm13:$b)), (CMPri $a, (as_i32imm $b))>;
+def : Pat<(SPcmpicc i64:$lhs, i64:$rhs), (SUBCCrr $lhs, $rhs)>;
+def : Pat<(SPcmpicc i64:$lhs, (i64 simm13:$rhs)), (SUBCCri $lhs, imm:$rhs)>;
 def : Pat<(i64 (ctpop i64:$src)), (POPCrr $src)>;
 
 } // Predicates = [Is64Bit]

llvm/lib/Target/Sparc/SparcInstrAliases.td

@@ -413,10 +413,13 @@ defm : reg_cond_alias<"gez",  0b111>;
 // non-alias form, except for the most obvious and clarifying aliases: cmp, jmp,
 // call, tst, ret, retl.
 
-// Note: cmp is handled in SparcInstrInfo.
-//       jmp/call/ret/retl have special case handling for output in
+// Note: jmp/call/ret/retl have special case handling for output in
 //       SparcInstPrinter.cpp
 
+// cmp rs1, reg_or_imm -> subcc rs1, reg_or_imm, %g0
+def : InstAlias<"cmp $rs1, $rs2", (SUBCCrr G0, IntRegs:$rs1, IntRegs:$rs2)>;
+def : InstAlias<"cmp $rs1, $imm", (SUBCCri G0, IntRegs:$rs1, simm13Op:$imm)>;
+
 // jmp addr -> jmpl addr, %g0
 def : InstAlias<"jmp $addr", (JMPLrr G0, MEMrr:$addr), 0>;
 def : InstAlias<"jmp $addr", (JMPLri G0, MEMri:$addr), 0>;

llvm/lib/Target/Sparc/SparcInstrInfo.td

@@ -222,6 +222,7 @@ def calltarget : Operand<i32> {
 }
 
 def simm13Op : Operand<iPTR> {
+  let OperandType = "OPERAND_IMMEDIATE";
   let DecoderMethod = "DecodeSIMM13";
   let EncoderMethod = "getSImm13OpValue";
 }
@@ -829,23 +830,14 @@ defm SUB    : F3_12  <"sub"  , 0b000100, sub, IntRegs, i32, simm13Op>;
 let Uses = [ICC], Defs = [ICC] in
   defm SUBE   : F3_12  <"subxcc" , 0b011100, sube, IntRegs, i32, simm13Op>;
 
-let Defs = [ICC] in
+let Defs = [ICC], hasPostISelHook = true in
   defm SUBCC  : F3_12  <"subcc", 0b010100, subc, IntRegs, i32, simm13Op>;
 
 let Uses = [ICC] in
   defm SUBC   : F3_12np <"subx", 0b001100>;
 
-// cmp (from Section A.3) is a specialized alias for subcc
-let Defs = [ICC], rd = 0 in {
-  def CMPrr   : F3_1<2, 0b010100,
-                     (outs), (ins IntRegs:$rs1, IntRegs:$rs2),
-                     "cmp $rs1, $rs2",
-                     [(SPcmpicc i32:$rs1, i32:$rs2)]>;
-  def CMPri   : F3_2<2, 0b010100,
-                     (outs), (ins IntRegs:$rs1, simm13Op:$simm13),
-                     "cmp $rs1, $simm13",
-                     [(SPcmpicc i32:$rs1, (i32 simm13:$simm13))]>;
-}
+def : Pat<(SPcmpicc i32:$lhs, i32:$rhs), (SUBCCrr $lhs, $rhs)>;
+def : Pat<(SPcmpicc i32:$lhs, (i32 simm13:$rhs)), (SUBCCri $lhs, imm:$rhs)>;
 
 // Section B.18 - Multiply Instructions, p. 113
 let Defs = [Y] in {