Sanity check to detect LLVM bug 96267

Author: luke-jr

src/kernel/checks.cpp

@@ -13,12 +13,30 @@
 
 namespace kernel {
 
+bool Clang_IndVarSimplify_Bug_SanityCheck() {
+    // See https://github.com/llvm/llvm-project/issues/96267
+    const char s[] = {0, 0x75};
+    signed int last = 0xff;
+    for (const char *it = s; it < &s[2]; ++it) {
+        if (*it <= 0x4e) {
+        } else if (*it == 0x75 && last <= 0x4e) {
+            return true;
+        }
+        last = *it;
+    }
+    return false;
+}
+
 util::Result<void> SanityChecks(const Context&)
 {
     if (auto result{dbwrapper_SanityCheck()}; !result) {
         return util::Error{util::ErrorString(result) + Untranslated("\nDatabase sanity check failure. Aborting.")};
     }
 
+    if (!Clang_IndVarSimplify_Bug_SanityCheck()) {
+        return util::Error{Untranslated("Compiler optimization sanity check failure. Aborting.")};
+    }
+
     if (!Random_SanityCheck()) {
         return util::Error{Untranslated("OS cryptographic RNG sanity check failure. Aborting.")};
     }

src/kernel/checks.h

@@ -11,6 +11,8 @@ namespace kernel {
 
 struct Context;
 
+[[nodiscard]] bool Clang_IndVarSimplify_Bug_SanityCheck();
+
 /**
  *  Ensure a usable environment with all necessary library support.
  */

src/test/sanity_tests.cpp

@@ -3,6 +3,7 @@
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <dbwrapper.h>
+#include <kernel/checks.h>
 #include <key.h>
 #include <test/util/setup_common.h>
 
@@ -13,6 +14,7 @@ BOOST_FIXTURE_TEST_SUITE(sanity_tests, BasicTestingSetup)
 BOOST_AUTO_TEST_CASE(basic_sanity)
 {
   BOOST_CHECK_MESSAGE(dbwrapper_SanityCheck(), "dbwrapper sanity test");
+  BOOST_CHECK_MESSAGE(kernel::Clang_IndVarSimplify_Bug_SanityCheck() == true, "Clang IndVarSimplify bug sanity test");
   BOOST_CHECK_MESSAGE(ECC_InitSanityCheck() == true, "secp256k1 sanity test");
 }