Fix segfault related to __builtin_unreachable with inline asm

Author: antoyo

src/context.rs

@@ -220,7 +220,7 @@ impl<'gcc, 'tcx> CodegenCx<'gcc, 'tcx> {
         let bool_type = context.new_type::<bool>();
 
         let mut functions = FxHashMap::default();
-        let builtins = ["abort"];
+        let builtins = ["abort", "__builtin_unreachable"];
 
         for builtin in builtins.iter() {
             functions.insert(builtin.to_string(), context.get_builtin_function(builtin));

tests/run/unreachable-function.rs

@@ -0,0 +1,23 @@
+// Compiler:
+//
+// Run-time:
+//   status: 0
+
+use std::arch::asm;
+
+fn exit_syscall(status: i32) -> ! {
+    unsafe {
+        asm!(
+            "syscall",
+            in("rax") 60,  // assuming x86_64 Linux
+            in("rdi") status,
+            options(noreturn)
+        );
+    }
+}
+
+fn main() {
+    // Used to crash with rustc_codegen_gcc.
+    exit_syscall(0);
+    std::process::exit(1);
+}