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

[Arthur Eubanks via cfe-commits]

================
@@ -424,11 +490,129 @@ 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:
+            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")
+
+        self.opt_level = extract_opt_level(self.clang_args) or "-O2"
+        backend_result = self.check_backend()
+        if backend_result == FailureType.BackEnd:
+            return backend_result
+
+        # Try running w/ -emit-llvm to generate an IR file,
+        # if it succeeds we have a backend failure, and can use llc.
+        if not self.check_expected_output(
+            args=self.clang_args + ["-emit-llvm", "-o", self.ir_file]
+        ):
+            print("Checking llc for failure")
+            if self.check_expected_output(
+                cmd=self.llc,
+                args=[self.opt_level, "-filetype=obj"],
+                filename=self.ir_file,
+            ):
+                print("Found BackEnd Crash")
+                return FailureType.BackEnd
+            elif os.path.exists(self.ir_file):
+                # clean up the IR file if we generated it, but won't use it.
+                print(f"clean up {self.ir_file}, since we can't repro w/ llc")
+                os.remove(self.ir_file)
+
+        # The IR file will be in 'self.ir_file'
+        self.extract_crashing_ir()
+        return self.check_middle_end()
+
+    def check_llc_failure(self) -> bool:
+        return self.check_expected_output(
+            cmd=self.llc, args=[self.opt_level, "-filetype=obj"], filename=self.ir_file
+        )
+
+    def extract_backend_ir(self) -> bool:
+        return not self.check_expected_output(
+            args=self.clang_args + ["-emit-llvm", "-o", self.ir_file]
+        )
+
+    def check_backend(self) -> Optional[FailureType]:
+        # Try running w/ -emit-llvm to generate an IR file,
+        # if it succeeds we have a backend failure, and can use llc.
+        if self.extract_backend_ir():
+            print("Checking llc for failure")
+            if self.check_llc_failure():
+                print("Found BackEnd Crash")
+                return FailureType.BackEnd
+            elif os.path.exists(self.ir_file):
+                # clean up the IR file if we generated it, but won't use it.
+                print(f"clean up {self.ir_file}, since we can't repro w/ llc")
+                os.remove(self.ir_file)
+
+    def extract_crashing_ir(self):
+        """
+        Extract IR just before the crash using --print-on-crash
+        """
+        args = self.clang_args + [
+            "-mllvm",
+            "--print-on-crash",
+            "-mllvm",
+            f"--print-on-crash-path={self.ir_file}",
+            "-mllvm",
+            "--print-module-scope",
+        ]
+
+        if not self.check_expected_output(args=args):
+            sys.exit("The interestingness test does not pass with '--print-on-crash'.")
+
+        # The output from --print-on-crash has an invalid first line (pass name).
+        remove_first_line(self.ir_file)
----------------
aeubanks wrote:

we should change the extra line to start with `;` to avoid having to do this (I've also been annoyed with this in the past). lemme have someone make this change to get into the LLVM development workflow

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