various fixes for naked_asm! implementation

- fix for divergence
- fix error message
- fix another cranelift test
- fix some cranelift things
- don't set the NORETURN option for naked asm
- fix use of naked_asm! in doc comment
- fix use of naked_asm! in run-make test
- use `span_bug` in unreachable branch

compiler/rustc_codegen_ssa/src/mir/block.rs

@@ -3,7 +3,9 @@ use std::cmp;
 use rustc_ast as ast;
 use rustc_ast::{InlineAsmOptions, InlineAsmTemplatePiece};
 use rustc_hir::lang_items::LangItem;
-use rustc_middle::mir::{self, AssertKind, BasicBlock, SwitchTargets, UnwindTerminateReason};
+use rustc_middle::mir::{
+    self, AssertKind, BasicBlock, InlineAsmMacro, SwitchTargets, UnwindTerminateReason,
+};
 use rustc_middle::ty::layout::{HasTyCtxt, LayoutOf, ValidityRequirement};
 use rustc_middle::ty::print::{with_no_trimmed_paths, with_no_visible_paths};
 use rustc_middle::ty::{self, Instance, Ty};
@@ -1133,6 +1135,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         &mut self,
         helper: TerminatorCodegenHelper<'tcx>,
         bx: &mut Bx,
+        asm_macro: InlineAsmMacro,
         terminator: &mir::Terminator<'tcx>,
         template: &[ast::InlineAsmTemplatePiece],
         operands: &[mir::InlineAsmOperand<'tcx>],
@@ -1203,11 +1206,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             &operands,
             options,
             line_spans,
-            if options.contains(InlineAsmOptions::NORETURN) {
-                None
-            } else {
-                targets.get(0).copied()
-            },
+            if asm_macro.diverges(options) { None } else { targets.get(0).copied() },
             unwind,
             instance,
             mergeable_succ,
@@ -1381,6 +1380,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             }
 
             mir::TerminatorKind::InlineAsm {
+                asm_macro,
                 template,
                 ref operands,
                 options,
@@ -1390,6 +1390,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             } => self.codegen_asm_terminator(
                 helper,
                 bx,
+                asm_macro,
                 terminator,
                 template,
                 operands,