Add a codegen switch for LLVM IR verification (#3107)

This is useful for diagnosing failures "in the field".

Author: SingleAccretion

src/coreclr/jit/jitconfigvalues.h

@@ -845,6 +845,7 @@ CONFIG_INTEGER(JitDispIns, "JitDispIns", 0)
 #endif // defined(TARGET_LOONGARCH64)
 
 #ifdef TARGET_WASM
+RELEASE_CONFIG_INTEGER(JitVerifyLlvmIR, "JitVerifyLlvmIR", 0)
 RELEASE_CONFIG_INTEGER(JitCheckLlvmIR, "JitCheckLlvmIR", 0)
 RELEASE_CONFIG_INTEGER(JitRunLssaTests, "JitRunLssaTests", 0)
 RELEASE_CONFIG_INTEGER(JitGcStress, "JitGcStress", 0)

src/coreclr/jit/llvm.cpp

@@ -856,6 +856,15 @@ static void FinishSingleThreadedCompilation(SingleThreadedCompilationContext* co
         module.addModuleFlag(llvm::Module::Warning, "Debug Info Version", 3);
     }
 
+    if (JitConfig.JitVerifyLlvmIR())
+    {
+        // Serialize verification so that the results are more legible.
+        static CritSecObject s_verifyLock;
+        CritSecHolder verifyLock(s_verifyLock);
+        llvm::errs() << "Verifying: '" << module.getName() << "'\n";
+        llvm::verifyModule(module, &llvm::errs());
+    }
+
     std::error_code code;
     StringRef outputFilePath = module.getName();
     if (JitConfig.JitCheckLlvmIR())