user0/rust
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

Rename -Zno-jump-tables to -Zjump-tables=<bool>

Browse source 
Both gcc and llvm accept -fjump-tables as well as -fno-jump-tables. For
consistency, allow rustc to accept -Zjump-tables=yes too.
This commit is contained in:
Paul Murphy 2025-08-28 14:44:34 -05:00
parent 35ebdf9ba1
commit 4959d18a97
7 changed files with 31 additions and 29 deletions
Download patch file Download diff file Expand all files Collapse all files

2
compiler/rustc_codegen_llvm/src/attributes.rs
View file

@ -229,7 +229,7 @@ fn instrument_function_attr<'ll>(
}
fn nojumptables_attr<'ll>(cx: &SimpleCx<'ll>, sess: &Session) -> Option<&'ll Attribute> {
if !sess.opts.unstable_opts.no_jump_tables {
if sess.opts.unstable_opts.jump_tables {
return None;
}

2
compiler/rustc_interface/src/tests.rs
View file

@ -814,6 +814,7 @@ fn test_unstable_options_tracking_hash() {
tracked!(inline_mir_threshold, Some(123));
tracked!(instrument_mcount, true);
tracked!(instrument_xray, Some(InstrumentXRay::default()));
tracked!(jump_tables, false);
tracked!(link_directives, false);
tracked!(link_only, true);
tracked!(lint_llvm_ir, true);
@ -831,7 +832,6 @@ fn test_unstable_options_tracking_hash() {
tracked!(mutable_noalias, false);
tracked!(next_solver, NextSolverConfig { coherence: true, globally: true });
tracked!(no_generate_arange_section, true);
tracked!(no_jump_tables, true);
tracked!(no_link, true);
tracked!(no_profiler_runtime, true);
tracked!(no_trait_vptr, true);

4
compiler/rustc_session/src/options.rs
View file

@ -2395,6 +2395,8 @@ options! {
`=skip-entry`
`=skip-exit`
Multiple options can be combined with commas."),
jump_tables: bool = (true, parse_bool, [TRACKED],
"allow jump table and lookup table generation from switch case lowering (default: yes)"),
layout_seed: Option<u64> = (None, parse_opt_number, [TRACKED],
"seed layout randomization"),
link_directives: bool = (true, parse_bool, [TRACKED],
@ -2475,8 +2477,6 @@ options! {
"omit DWARF address ranges that give faster lookups"),
no_implied_bounds_compat: bool = (false, parse_bool, [TRACKED],
"disable the compatibility version of the `implied_bounds_ty` query"),
no_jump_tables: bool = (false, parse_no_value, [TRACKED],
"disable the jump tables and lookup tables that can be generated from a switch case lowering"),
no_leak_check: bool = (false, parse_no_value, [UNTRACKED],
"disable the 'leak check' for subtyping; unsound, but useful for tests"),
no_link: bool = (false, parse_no_value, [TRACKED],

19
src/doc/unstable-book/src/compiler-flags/jump-tables.md Normal file
View file

@ -0,0 +1,19 @@
# `jump-tables`
The tracking issue for this feature is [#116592](https://github.com/rust-lang/rust/issues/116592)
---
When set to no, this option enables the `-fno-jump-tables` flag for LLVM, which makes the
codegen backend avoid generating jump tables when lowering switches.
When set to no, this option adds the LLVM `no-jump-tables=true` attribute to every function.
Disabling jump tables can be used to help provide protection against
jump-oriented-programming (JOP) attacks, such as with the linux kernel's [IBT].
```sh
RUSTFLAGS="-Zjump-tables=no" cargo +nightly build -Z build-std
```
[IBT]: https://www.phoronix.com/news/Linux-IBT-By-Default-Tip

19
src/doc/unstable-book/src/compiler-flags/no-jump-tables.md
View file

@ -1,19 +0,0 @@
# `no-jump-tables`
The tracking issue for this feature is [#116592](https://github.com/rust-lang/rust/issues/116592)
---
This option enables the `-fno-jump-tables` flag for LLVM, which makes the
codegen backend avoid generating jump tables when lowering switches.
This option adds the LLVM `no-jump-tables=true` attribute to every function.
The option can be used to help provide protection against
jump-oriented-programming (JOP) attacks, such as with the linux kernel's [IBT].
```sh
RUSTFLAGS="-Zno-jump-tables" cargo +nightly build -Z build-std
```
[IBT]: https://www.phoronix.com/news/Linux-IBT-By-Default-Tip

4
tests/assembly-llvm/x86_64-no-jump-tables.rs
View file

@ -1,10 +1,10 @@
// Test that jump tables are (not) emitted when the `-Zno-jump-tables`
// Test that jump tables are (not) emitted when the `-Zjump-tables=no`
// flag is (not) set.
//@ revisions: unset set
//@ assembly-output: emit-asm
//@ compile-flags: -Copt-level=3
//@ [set] compile-flags: -Zno-jump-tables
//@ [set] compile-flags: -Zjump-tables=no
//@ only-x86_64
//@ ignore-sgx

10
tests/codegen-llvm/no-jump-tables.rs
View file

@ -1,11 +1,12 @@
// Test that the `no-jump-tables` function attribute are (not) emitted when
// the `-Zno-jump-tables` flag is (not) set.
// the `-Zjump-tables=no` flag is (not) set.
//@ add-minicore
//@ revisions: unset set
//@ revisions: unset set_no set_yes
//@ needs-llvm-components: x86
//@ compile-flags: --target x86_64-unknown-linux-gnu
//@ [set] compile-flags: -Zno-jump-tables
//@ [set_no] compile-flags: -Zjump-tables=no
//@ [set_yes] compile-flags: -Zjump-tables=yes
#![crate_type = "lib"]
#![feature(no_core, lang_items)]
@ -19,5 +20,6 @@ pub fn foo() {
// CHECK: @foo() unnamed_addr #0
// unset-NOT: attributes #0 = { {{.*}}"no-jump-tables"="true"{{.*}} }
// set: attributes #0 = { {{.*}}"no-jump-tables"="true"{{.*}} }
// set_yes-NOT: attributes #0 = { {{.*}}"no-jump-tables"="true"{{.*}} }
// set_no: attributes #0 = { {{.*}}"no-jump-tables"="true"{{.*}} }
}