Merge pull request #308 from nathanchance/apple-silicon-conservative-instrumentation

Author: msfjarvis

tc_build/llvm.py

@@ -78,6 +78,13 @@ def bolt_clang(self):
                 clang_inst,
                 clang,
             ]
+            # When running an instrumented binary on certain platforms (namely
+            # Apple Silicon), there may be hangs due to instrumentation in
+            # between exclusive load and store instructions:
+            # https://github.com/llvm/llvm-project/issues/153492
+            # Enable conservative instrumentation to avoid this.
+            if tc_build.utils.cpu_is_apple_silicon():
+                clang_inst_cmd.append('--conservative-instrumentation')
             self.run_cmd(clang_inst_cmd)
 
             self.bolt_builder.bolt_instrumentation = True

tc_build/utils.py

@@ -1,10 +1,21 @@
 #!/usr/bin/env python3
 
+from pathlib import Path
 import subprocess
 import sys
+import re
 import time
 
 
+def cpu_is_apple_silicon():
+    cpuinfo = Path('/proc/cpuinfo').read_text(encoding='utf-8')
+    if match := re.search(r"implementer\s+:\s+(\w+)", cpuinfo):
+        # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/include/asm/cputype.h?h=v6.17-rc4#n62
+        return match.groups()[0] == '0x61'
+    # If we cannot prove that it is Apple Silicon, we assume it is not
+    return False
+
+
 def create_gitignore(folder):
     folder.joinpath('.gitignore').write_text('*\n', encoding='utf-8')