[mlir] Sanitize identifiers with leading symbol. (llvm#94795)

Presently, if name starts with a symbol it's converted to hex which may
cause the result to be invalid by starting with a digit.

Address this and add a small test.

Co-authored-by: Will Dietz <w@wdtz.org>

mlir/lib/IR/AsmPrinter.cpp

@@ -999,9 +999,13 @@ static StringRef sanitizeIdentifier(StringRef name, SmallString<16> &buffer,
                                     bool allowTrailingDigit = true) {
   assert(!name.empty() && "Shouldn't have an empty name here");
 
+  auto validChar = [&](char ch) {
+    return llvm::isAlnum(ch) || allowedPunctChars.contains(ch);
+  };
+
   auto copyNameToBuffer = [&] {
     for (char ch : name) {
-      if (llvm::isAlnum(ch) || allowedPunctChars.contains(ch))
+      if (validChar(ch))
         buffer.push_back(ch);
       else if (ch == ' ')
         buffer.push_back('_');
@@ -1013,7 +1017,7 @@ static StringRef sanitizeIdentifier(StringRef name, SmallString<16> &buffer,
   // Check to see if this name is valid. If it starts with a digit, then it
   // could conflict with the autogenerated numeric ID's, so add an underscore
   // prefix to avoid problems.
-  if (isdigit(name[0])) {
+  if (isdigit(name[0]) || (!validChar(name[0]) && name[0] != ' ')) {
     buffer.push_back('_');
     copyNameToBuffer();
     return buffer;
@@ -1029,7 +1033,7 @@ static StringRef sanitizeIdentifier(StringRef name, SmallString<16> &buffer,
 
   // Check to see that the name consists of only valid identifier characters.
   for (char ch : name) {
-    if (!llvm::isAlnum(ch) && !allowedPunctChars.contains(ch)) {
+    if (!validChar(ch)) {
       copyNameToBuffer();
       return buffer;
     }

mlir/test/IR/print-attr-type-aliases.mlir

@@ -11,6 +11,9 @@
 // CHECK-DAG: #_0_test_alias = "alias_test:prefixed_digit"
 "test.op"() {alias_test = "alias_test:prefixed_digit"} : () -> ()
 
+// CHECK-DAG: #_25test = "alias_test:prefixed_symbol"
+"test.op"() {alias_test = "alias_test:prefixed_symbol"} : () -> ()
+
 // CHECK-DAG: #test_alias_conflict0_ = "alias_test:sanitize_conflict_a"
 // CHECK-DAG: #test_alias_conflict0_1 = "alias_test:sanitize_conflict_b"
 "test.op"() {alias_test = ["alias_test:sanitize_conflict_a", "alias_test:sanitize_conflict_b"]} : () -> ()

mlir/test/lib/Dialect/Test/TestDialectInterfaces.cpp

@@ -188,6 +188,7 @@ struct TestOpAsmInterface : public OpAsmDialectInterface {
             .Case("alias_test:dot_in_name", StringRef("test.alias"))
             .Case("alias_test:trailing_digit", StringRef("test_alias0"))
             .Case("alias_test:prefixed_digit", StringRef("0_test_alias"))
+            .Case("alias_test:prefixed_symbol", StringRef("%test"))
             .Case("alias_test:sanitize_conflict_a",
                   StringRef("test_alias_conflict0"))
             .Case("alias_test:sanitize_conflict_b",