[clang] [clang][utils] Add auto mode to reduction script (PR #163282)

[Paul Kirth via cfe-commits]

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@@ -424,11 +490,76 @@ def run_creduce(self):
             print("\n\nctrl-c detected, killed reduction tool")
             p.kill()
 
+    def run_llvm_reduce(self):
+        full_llvm_reduce_cmd = [
+            llvm_reduce_cmd,
+            f"--test={self.testfile}",
+            self.ir_file,
+        ]
+        print("\nRunning llvm-reduce tool...")
+        verbose_print(quote_cmd(full_llvm_reduce_cmd))
+        try:
+            p = subprocess.Popen(full_llvm_reduce_cmd)
+            p.communicate()
+        except KeyboardInterrupt:
+            # Hack to kill C-Reduce because it jumps into its own pgid
+            print("\n\nctrl-c detected, killed reduction tool")
+            p.kill()
+
+    def classify_crash(self) -> FailureType:
+        print("classifying crash ...")
+        if self.check_expected_output(args=self.clang_args + ["-fsyntax-only"]):
+            print("Found Frontend Crash")
+            return FailureType.FrontEnd
+
+        print("Found Middle/Backend failure")
+        args = self.clang_args + [
+            "-mllvm",
+            "--print-on-crash",
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ilovepi wrote:

I factored this logic into some methods, that way if we want to switch the mechanism it should be slightly easier.

https://github.com/llvm/llvm-project/pull/163282