[AArch64] Add BRB IALL and BRB INJ instructions

BRB IALL: Invalidate the Branch Record Buffer
BRB INJ: Branch Record Injection into the Branch Record Buffer

Parser changes based on work by Simon Tatham.

These are two-word mnemonics. The assembly parser works by special-casing
the mnemonic in order to parse the second word as a plain identifier token.

Reviewed by: MarkMurrayARM

Differential Revision: https://reviews.llvm.org/D93899

Author: tmatheson-arm

llvm/lib/Target/AArch64/AArch64InstrInfo.td

@@ -813,7 +813,21 @@ def WFET : RegInputSystemI<0b0000, 0b000, "wfet">;
 def WFIT : RegInputSystemI<0b0000, 0b001, "wfit">;
 }
 
+// Branch Record Buffer two-word mnemonic instructions
+class BRBEI<bits<3> op2, string keyword>
+    : SimpleSystemI<0, (ins), "brb", keyword>, Sched<[WriteSys]> {
+  let Inst{31-8} = 0b110101010000100101110010;
+  let Inst{7-5} = op2;
+  let Predicates = [HasBRBE];
 }
+def BRB_IALL: BRBEI<0b100, "\tiall">;
+def BRB_INJ:  BRBEI<0b101, "\tinj">;
+
+}
+
+// Allow uppercase and lowercase keyword arguments for BRB IALL and BRB INJ
+def : TokenAlias<"INJ", "inj">;
+def : TokenAlias<"IALL", "iall">;
 
 // ARMv8.2-A Dot Product
 let Predicates = [HasDotProd] in {

llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp

@@ -159,6 +159,7 @@ class AArch64AsmParser : public MCTargetAsmParser {
   bool parseSymbolicImmVal(const MCExpr *&ImmVal);
   bool parseNeonVectorList(OperandVector &Operands);
   bool parseOptionalMulOperand(OperandVector &Operands);
+  bool parseKeywordOperand(OperandVector &Operands);
   bool parseOperand(OperandVector &Operands, bool isCondCode,
                     bool invertCondCode);
   bool parseImmExpr(int64_t &Out);
@@ -3701,6 +3702,17 @@ bool AArch64AsmParser::parseOptionalMulOperand(OperandVector &Operands) {
   return Error(getLoc(), "expected 'vl' or '#<imm>'");
 }
 
+bool AArch64AsmParser::parseKeywordOperand(OperandVector &Operands) {
+  MCAsmParser &Parser = getParser();
+  auto Tok = Parser.getTok();
+  if (Tok.isNot(AsmToken::Identifier))
+    return true;
+  Operands.push_back(AArch64Operand::CreateToken(Tok.getString(), false,
+                                                 Tok.getLoc(), getContext()));
+  Parser.Lex();
+  return false;
+}
+
 /// parseOperand - Parse a arm instruction operand.  For now this parses the
 /// operand regardless of the mnemonic.
 bool AArch64AsmParser::parseOperand(OperandVector &Operands, bool isCondCode,
@@ -3765,6 +3777,11 @@ bool AArch64AsmParser::parseOperand(OperandVector &Operands, bool isCondCode,
     if (GotShift != MatchOperand_NoMatch)
       return GotShift;
 
+    // If this is a two-word mnemonic, parse its special keyword
+    // operand as an identifier.
+    if (Mnemonic == "brb")
+      return parseKeywordOperand(Operands);
+
     // This was not a register so parse other operands that start with an
     // identifier (like labels) as expressions and create them as immediates.
     const MCExpr *IdVal;

llvm/test/MC/AArch64/brbe.s

@@ -133,3 +133,17 @@ mrs x5, BRBTGT31_EL1
 // CHECK: mrs     x5, BRBTGT31_EL1        // encoding: [0xc5,0x8f,0x31,0xd5]
 // ERROR-NO-BRBE: [[@LINE-4]]:5: error: expected writable system register
 // ERROR-NO-BRBE: [[@LINE-4]]:9: error: expected readable system register
+
+brb iall
+brb inj
+// CHECK: brb iall  // encoding: [0x9f,0x72,0x09,0xd5]
+// CHECK: brb inj   // encoding: [0xbf,0x72,0x09,0xd5]
+// ERROR-NO-BRBE: [[@LINE-4]]:1: error: instruction requires: brbe
+// ERROR-NO-BRBE: [[@LINE-4]]:1: error: instruction requires: brbe
+
+brb IALL
+brb INJ
+// CHECK: brb iall  // encoding: [0x9f,0x72,0x09,0xd5]
+// CHECK: brb inj   // encoding: [0xbf,0x72,0x09,0xd5]
+// ERROR-NO-BRBE: [[@LINE-4]]:1: error: instruction requires: brbe
+// ERROR-NO-BRBE: [[@LINE-4]]:1: error: instruction requires: brbe