--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/llvm/test/TableGen/MixedCasedMnemonic.td	Tue Jun 08 06:07:14 2021 +0900
@@ -0,0 +1,76 @@
+// RUN: llvm-tblgen -gen-asm-matcher -I %p/../../include %s | FileCheck %s --check-prefix=MATCHER
+// RUN: llvm-tblgen -gen-asm-writer -I %p/../../include %s | FileCheck %s --check-prefix=WRITER
+// RUN: llvm-tblgen -gen-asm-matcher -I %p/../../include %s | FileCheck %s --check-prefix=ALIAS
+
+// Check that an instruction that uses mixed upper/lower case in its mnemonic
+// is printed as-is, and is parsed in its "canonicalized" lowercase form.
+
+include "llvm/Target/Target.td"
+
+def ArchInstrInfo : InstrInfo { }
+
+def Arch : Target {
+  let InstructionSet = ArchInstrInfo;
+}
+
+def Reg : Register<"reg">;
+def RegClass : RegisterClass<"foo", [i32], 0, (add Reg)>;
+
+// Define instructions that demonstrate case-insensitivity.
+// In case-sensitive ASCII order, "BInst" < "aInst".
+// In case-insensitive order, "aInst" < "BInst".
+// If the matcher really treats the mnemonics in a case-insensitive way,
+// then we should see "aInst" appearing before "BInst", despite the
+// fact that "BInst" would appear before "aInst" in ASCIIbetical order.
+def AlphabeticallySecondInst : Instruction {
+  let Size = 2;
+  let OutOperandList = (outs);
+  let InOperandList = (ins);
+  let AsmString = "BInst";
+}
+
+def AlphabeticallyFirstInst : Instruction {
+  let Size = 2;
+  let OutOperandList = (outs);
+  let InOperandList = (ins);
+  let AsmString = "aInst";
+}
+
+def :MnemonicAlias<"Insta", "aInst">;
+def :MnemonicAlias<"InstB", "BInst">;
+
+// Check that the matcher lower()s the mnemonics it matches.
+// MATCHER: static const char *const MnemonicTable =
+// MATCHER-NEXT: "\005ainst\005binst";
+
+// Check that aInst appears before BInst in the match table.
+// This shows that the mnemonics are sorted in a case-insensitive way,
+// since otherwise "B" would be less than "a" by ASCII order.
+// MATCHER:      static const MatchEntry MatchTable0[] = {
+// MATCHER-NEXT:     /* aInst */, ::AlphabeticallyFirstInst
+// MATCHER-NEXT:     /* BInst */, ::AlphabeticallySecondInst
+// MATCHER-NEXT: };
+
+// Check that the writer preserves the case of the mnemonics.
+// WRITER:      static const char AsmStrs[] = {
+// WRITER:        "BInst\0"
+// WRITER-NEXT:   "aInst\0"
+// WRITER-NEXT: };
+
+// ALIAS: static void applyMnemonicAliases(StringRef &Mnemonic, const FeatureBitset &Features, unsigned VariantID) {
+// ALIAS-NEXT  switch (VariantID) {
+// ALIAS-NEXT  case 0:
+// ALIAS-NEXT      switch (Mnemonic.size()) {
+// ALIAS-NEXT      default: break;
+// ALIAS-NEXT      case 5:	 // 2 strings to match.
+// ALIAS-NEXT        if (memcmp(Mnemonic.data()+0, "inst", 4) != 0)
+// ALIAS-NEXT          break;
+// ALIAS-NEXT        switch (Mnemonic[4]) {
+// ALIAS-NEXT        default: break;
+// ALIAS-NEXT        case 'a':	 // 1 string to match.
+// ALIAS-NEXT          Mnemonic = "ainst";	 // "insta"
+// ALIAS-NEXT          return;
+// ALIAS-NEXT        case 'b':	 // 1 string to match.
+// ALIAS-NEXT          Mnemonic = "binst";	 // "instb"
+// ALIAS-NEXT          return;
+