[AArch64][AsmParser] Cleanup isSImm7s4, isSImm7s8, (etc) functions.

[samparker]

Nice, LGTM. cheers!

[fhahn]

LGTM, looks like a useful NFC.

lib/Target/AArch64/AArch64InstrFormats.td

 // aaaaaaaa bbbbbbbb cccccccc dddddddd eeeeeeee ffffffff gggggggg hhhhhhhh
 // are encoded as the eight bit value 'abcdefgh'.
 def SIMDImmType10Operand : AsmOperandClass { let Name = "SIMDImmType10"; }
 
 // Authenticated loads for v8.3 can have scaled 10-bit immediate offsets.
 def SImm10s8Operand : AsmOperandClass {
   let Name = "SImm10s8";
   let DiagnosticType = "InvalidMemoryIndexedSImm10";
+  let PredicateMethod = "isSImmScaled<10, 8>";
 }
 
 //===----------------------------------------------------------------------===//
 // Operand Definitions.
 //
 
 // ADR[P] instruction labels.
 def AdrpOperand : AsmOperandClass {
def AdrOperand : AsmOperandClass {
   let ParserMethod = "tryParseAdrLabel";
   let DiagnosticType = "InvalidLabel";
 }
 def adrlabel : Operand<i64> {
   let EncoderMethod = "getAdrLabelOpValue";
   let ParserMatchClass = AdrOperand;
 }
 
+class SImmOperand<int width> : AsmOperandClass {
+  let Name = "SImm" # width;
+  let DiagnosticType = "InvalidMemoryIndexedSImm" # width;
+  let RenderMethod = "addImmOperands";
+  let PredicateMethod = "isSImm<" # width # ">";
+}
+
 def simm10Scaled : Operand<i64> {
   let ParserMatchClass = SImm10s8Operand;
   let DecoderMethod = "DecodeSImm<10>";
   let PrintMethod = "printImmScale<8>";
 }
 
-// simm9 predicate - True if the immediate is in the range [-256, 255].
-def SImm9Operand : AsmOperandClass {
-  let Name = "SImm9";
-  let DiagnosticType = "InvalidMemoryIndexedSImm9";
-}
+def SImm9Operand : SImmOperand<9>;
 def simm9 : Operand<i64>, ImmLeaf<i64, [{ return Imm >= -256 && Imm < 256; }]> {
   let ParserMatchClass = SImm9Operand;
+  let DecoderMethod = "DecodeSImm<9>";
 }
 
 // simm7sN predicate - True if the immediate is a multiple of N in the range
 // [-64 * N, 63 * N].
 class SImm7Scaled<int Scale> : AsmOperandClass {
   let Name = "SImm7s" # Scale;
   let DiagnosticType = "InvalidMemoryIndexed" # Scale # "SImm7";
+  let PredicateMethod = "isSImmScaled<7, " # Scale # ">";
 }
 
 def SImm7s4Operand : SImm7Scaled<4>;
 def SImm7s8Operand : SImm7Scaled<8>;
 def SImm7s16Operand : SImm7Scaled<16>;
 
 def simm7s4 : Operand<i32> {
   let ParserMatchClass = SImm7s4Operand;

lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp

public:
 
   bool hasShiftExtendAmount() const {
     assert(Kind == k_ShiftExtend && "Invalid access!");
     return ShiftExtend.HasExplicitAmount;
   }
 
   bool isImm() const override { return Kind == k_Immediate; }
   bool isMem() const override { return false; }
-  bool isSImm9() const {
-    if (!isImm())
-      return false;
-    const MCConstantExpr *MCE = dyn_cast<MCConstantExpr>(getImm());
-    if (!MCE)
-      return false;
-    int64_t Val = MCE->getValue();
-    return (Val >= -256 && Val < 256);
-  }
-  bool isSImm10s8() const {
-    if (!isImm())
-      return false;
-    const MCConstantExpr *MCE = dyn_cast<MCConstantExpr>(getImm());
-    if (!MCE)
-      return false;
-    int64_t Val = MCE->getValue();
-    return (Val >= -4096 && Val < 4089 && (Val & 7) == 0);
-  }
-  bool isSImm7s4() const {
-    if (!isImm())
-      return false;
-    const MCConstantExpr *MCE = dyn_cast<MCConstantExpr>(getImm());
-    if (!MCE)
-      return false;
-    int64_t Val = MCE->getValue();
-    return (Val >= -256 && Val <= 252 && (Val & 3) == 0);
-  }
-  bool isSImm7s8() const {
-    if (!isImm())
-      return false;
-    const MCConstantExpr *MCE = dyn_cast<MCConstantExpr>(getImm());
-    if (!MCE)
-      return false;
-    int64_t Val = MCE->getValue();
-    return (Val >= -512 && Val <= 504 && (Val & 7) == 0);
-  }
-  bool isSImm7s16() const {
+
+  template <int Width> bool isSImm() const { return isSImmScaled<Width, 1>(); }
+
+  template <int Bits, int Scale> bool isSImmScaled() const {
     if (!isImm())
       return false;
     const MCConstantExpr *MCE = dyn_cast<MCConstantExpr>(getImm());
     if (!MCE)
       return false;
+
+    int64_t Shift = Bits - 1;
+    int64_t MinVal = (int64_t(1) << Shift) * -Scale;
+    int64_t MaxVal = ((int64_t(1) << Shift) - 1) * Scale;
+
     int64_t Val = MCE->getValue();
-    return (Val >= -1024 && Val <= 1008 && (Val & 15) == 0);
+    return Val >= MinVal && Val <= MaxVal && (Val % Scale) == 0;
   }
 
   bool isSymbolicUImm12Offset(const MCExpr *Expr, unsigned Scale) const {
     AArch64MCExpr::VariantKind ELFRefKind;
     MCSymbolRefExpr::VariantKind DarwinRefKind;
     int64_t Addend;
     if (!AArch64AsmParser::classifySymbolRef(Expr, ELFRefKind, DarwinRefKind,
                                            Addend)) {
public:
 
   // Fallback unscaled operands are for aliases of LDR/STR that fall back
   // to LDUR/STUR when the offset is not legal for the former but is for
   // the latter. As such, in addition to checking for being a legal unscaled
   // address, also check that it is not a legal scaled address. This avoids
   // ambiguity in the matcher.
   template<int Width>
   bool isSImm9OffsetFB() const {
-    return isSImm9() && !isUImm12Offset<Width / 8>();
+    return isSImm<9>() && !isUImm12Offset<Width / 8>();
   }
 
   bool isAdrpLabel() const {
     // Validation was handled during parsing, so we just sanity check that
     // something didn't go haywire.
     if (!isImm())
         return false;