[llvm] cmake: Derive CMake system name from a triple via new mechanism (PR #208773)

[Alexis Engelke via llvm-commits]

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@@ -0,0 +1,155 @@
+#!/usr/bin/env python3
+"""Derive a CMake system name from a target triple.
+
+The recognized OS and environment names are defined in
+llvm/include/llvm/TargetParser/TripleName.def. This script parses that
+file so the CMake runtimes build can map a (possibly unnormalized)
+triple to a CMake system name without running a compiled tool. CMake
+invokes it once per target with --triple and reads the printed name.
+
+Modes:
+  --triple TRIPLE   Print the CMake system name for TRIPLE (empty if unknown or
+                    the triple has too few components; the caller then falls back
+                    to the host system name).
+
+Options:
+  --def-file PATH   Path to TripleName.def to parse instead of the copy located
+                    relative to this script (in llvm/include/llvm/TargetParser).
+
+"""
+
+import argparse
+import os
+import re
+import sys
+
+_OS_RE = re.compile(r'^\s*TRIPLE_OS\(\s*(\w+)\s*,\s*"([^"]*)"\s*,\s*"([^"]*)"\s*\)')
+_OS_ALIAS_RE = re.compile(r'^\s*TRIPLE_OS_ALIAS\(\s*(\w+)\s*,\s*"([^"]*)"\s*\)')
+_ENV_RE = re.compile(r'^\s*TRIPLE_ENV\(\s*(\w+)\s*,\s*"([^"]*)"\s*,\s*"([^"]*)"\s*\)')
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aengelke wrote:

I don't have a good feeling about this ad-hoc C preprocessor parsing...

https://github.com/llvm/llvm-project/pull/208773