[llvm] [LLVM][Option] Refactor option name comparison (PR #108219)

[Jan Svoboda via llvm-commits]

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@@ -0,0 +1,51 @@
+//===- OptStrCmp.h - Option String Comparison -------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_OPTION_OPTSTRCMP_H
+#define LLVM_OPTION_OPTSTRCMP_H
+
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/StringRef.h"
+
+namespace llvm::opt {
+
+// Comparison function for Option strings (option names & prefixes).
+// The ordering is *almost* case-insensitive lexicographic, with an exception.
+// '\0' comes at the end of the alphabet instead of the beginning (thus options
+// precede any other options which prefix them). Additionally, if two options
+// are identical ignoring case, they are ordered according to case sensitive
+// ordering if `FallbackCaseSensitive` is true.
+static int StrCmpOptionName(StringRef A, StringRef B,
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jansvoboda11 wrote:

Ah, I didn't notice this aspect of the patch. The simplest thing might be to put this header (and new `.cpp` file) into `Support`, which both `Option` and `TableGen` already depend on. Anything else besides introducing new library smells of a layering violation.

`Support` already contains another command-line parsing library in `CommandLine.{h,cpp}`, so adding these files there is not entirely without precedent.

https://github.com/llvm/llvm-project/pull/108219