From a65ec44779ab2c01ba937b40496ca648626d0308 Mon Sep 17 00:00:00 2001 From: Miguel Ojeda Date: Sat, 17 Dec 2022 02:50:08 +0100 Subject: Add `-Zno-jump-tables` This flag mimics GCC/Clang's `-fno-jump-tables` [1][2], which makes the codegen backend avoid generating jump tables when lowering switches. In the case of LLVM, the `"no-jump-tables"="true"` function attribute is added to every function. The kernel currently needs it for x86 when enabling IBT [3], as well as for Alpha (plus VDSO objects in MIPS/LoongArch). [1] https://gcc.gnu.org/onlinedocs/gcc/Code-Gen-Options.html#index-fno-jump-tables [2] https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-fjump-tables [3] https://github.com/torvalds/linux/blob/v6.1/arch/x86/Makefile#L75-L83 Signed-off-by: Miguel Ojeda --- src/test/codegen/no-jump-tables.rs | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) create mode 100644 src/test/codegen/no-jump-tables.rs (limited to 'src/test/codegen') diff --git a/src/test/codegen/no-jump-tables.rs b/src/test/codegen/no-jump-tables.rs new file mode 100644 index 00000000000..8e2cb47566e --- /dev/null +++ b/src/test/codegen/no-jump-tables.rs @@ -0,0 +1,22 @@ +// Test that the `no-jump-tables` function attribute are (not) emitted when +// the `-Zno-jump-tables` flag is (not) set. + +// revisions: unset set +// needs-llvm-components: x86 +// compile-flags: --target x86_64-unknown-linux-gnu +// [set] compile-flags: -Zno-jump-tables + +#![crate_type = "lib"] +#![feature(no_core, lang_items)] +#![no_core] + +#[lang = "sized"] +trait Sized {} + +#[no_mangle] +pub fn foo() { + // CHECK: @foo() unnamed_addr #0 + + // unset-NOT: attributes #0 = { {{.*}}"no-jump-tables"="true"{{.*}} } + // set: attributes #0 = { {{.*}}"no-jump-tables"="true"{{.*}} } +} -- cgit 1.4.1-3-g733a5