[AArch64] Suggest b.nfrst if the user tries b.nfirst.

Differential Revision: https://reviews.llvm.org/D119453

Co-authored-by: George Steed <george.steed@arm.com>

Author: MDevereau

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

@@ -157,7 +157,8 @@ class AArch64AsmParser : public MCTargetAsmParser {
 
   bool parseSysAlias(StringRef Name, SMLoc NameLoc, OperandVector &Operands);
   void createSysAlias(uint16_t Encoding, OperandVector &Operands, SMLoc S);
-  AArch64CC::CondCode parseCondCodeString(StringRef Cond);
+  AArch64CC::CondCode parseCondCodeString(StringRef Cond,
+                                          std::string &Suggestion);
   bool parseCondCode(OperandVector &Operands, bool invertCondCode);
   unsigned matchRegisterNameAlias(StringRef Name, RegKind Kind);
   bool parseRegister(OperandVector &Operands);
@@ -3029,8 +3030,10 @@ AArch64AsmParser::tryParseImmWithOptionalShift(OperandVector &Operands) {
   return MatchOperand_Success;
 }
 
-/// parseCondCodeString - Parse a Condition Code string.
-AArch64CC::CondCode AArch64AsmParser::parseCondCodeString(StringRef Cond) {
+/// parseCondCodeString - Parse a Condition Code string, optionally returning a
+/// suggestion to help common typos.
+AArch64CC::CondCode
+AArch64AsmParser::parseCondCodeString(StringRef Cond, std::string &Suggestion) {
   AArch64CC::CondCode CC = StringSwitch<AArch64CC::CondCode>(Cond.lower())
                     .Case("eq", AArch64CC::EQ)
                     .Case("ne", AArch64CC::NE)
@@ -3053,7 +3056,7 @@ AArch64CC::CondCode AArch64AsmParser::parseCondCodeString(StringRef Cond) {
                     .Default(AArch64CC::Invalid);
 
   if (CC == AArch64CC::Invalid &&
-      getSTI().getFeatureBits()[AArch64::FeatureSVE])
+      getSTI().getFeatureBits()[AArch64::FeatureSVE]) {
     CC = StringSwitch<AArch64CC::CondCode>(Cond.lower())
                     .Case("none",  AArch64CC::EQ)
                     .Case("any",   AArch64CC::NE)
@@ -3067,6 +3070,9 @@ AArch64CC::CondCode AArch64AsmParser::parseCondCodeString(StringRef Cond) {
                     .Case("tstop", AArch64CC::LT)
                     .Default(AArch64CC::Invalid);
 
+    if (CC == AArch64CC::Invalid && Cond.lower() == "nfirst")
+      Suggestion = "nfrst";
+  }
   return CC;
 }
 
@@ -3078,9 +3084,14 @@ bool AArch64AsmParser::parseCondCode(OperandVector &Operands,
   assert(Tok.is(AsmToken::Identifier) && "Token is not an Identifier");
 
   StringRef Cond = Tok.getString();
-  AArch64CC::CondCode CC = parseCondCodeString(Cond);
-  if (CC == AArch64CC::Invalid)
-    return TokError("invalid condition code");
+  std::string Suggestion;
+  AArch64CC::CondCode CC = parseCondCodeString(Cond, Suggestion);
+  if (CC == AArch64CC::Invalid) {
+    std::string Msg = "invalid condition code";
+    if (!Suggestion.empty())
+      Msg += ", did you mean " + Suggestion + "?";
+    return TokError(Msg);
+  }
   Lex(); // Eat identifier token.
 
   if (invertCondCode) {
@@ -4545,9 +4556,14 @@ bool AArch64AsmParser::ParseInstruction(ParseInstructionInfo &Info,
 
     SMLoc SuffixLoc = SMLoc::getFromPointer(NameLoc.getPointer() +
                                             (Head.data() - Name.data()));
-    AArch64CC::CondCode CC = parseCondCodeString(Head);
-    if (CC == AArch64CC::Invalid)
-      return Error(SuffixLoc, "invalid condition code");
+    std::string Suggestion;
+    AArch64CC::CondCode CC = parseCondCodeString(Head, Suggestion);
+    if (CC == AArch64CC::Invalid) {
+      std::string Msg = "invalid condition code";
+      if (!Suggestion.empty())
+        Msg += ", did you mean " + Suggestion + "?";
+      return Error(SuffixLoc, Msg);
+    }
     Operands.push_back(AArch64Operand::CreateToken(".", SuffixLoc, getContext(),
                                                    /*IsSuffix=*/true));
     Operands.push_back(

llvm/test/MC/AArch64/SVE/condtion-code-diagnostics.s

@@ -0,0 +1,9 @@
+// RUN: not llvm-mc -triple aarch64 -show-encoding -mattr=+sve < %s 2>&1 | FileCheck %s
+
+//------------------------------------------------------------------------------
+// Condition code diagnostics for SVE
+//------------------------------------------------------------------------------
+
+        b.nfirst lbl
+// CHECK: [[@LINE-1]]:{{[0-9]+}}: error: invalid condition code, did you mean nfrst?
+// CHECK-NEXT:  b.nfirst lbl