Fix segfault related to __builtin_unreachable with inline asm

Author: antoyo

src/asm.rs

@@ -575,9 +575,7 @@ impl<'a, 'gcc, 'tcx> AsmBuilderMethods<'tcx> for Builder<'a, 'gcc, 'tcx> {
         }
         if dest.is_none() && options.contains(InlineAsmOptions::NORETURN) {
             let builtin_unreachable = self.context.get_builtin_function("__builtin_unreachable");
-            let builtin_unreachable: RValue<'gcc> =
-                unsafe { std::mem::transmute(builtin_unreachable) };
-            self.call(self.type_void(), None, None, builtin_unreachable, &[], None, None);
+            let _ = self.context.new_call(None, builtin_unreachable, &[]);
         }
 
         // Write results to outputs.

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);
+}