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Forbid CHECK: br and CHECK-NOT: br in codegen tests (suggest br {{.*}} instead) #149190

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Forbid CHECK: br and CHECK-NOT: br in codegen tests (suggest br {{.*}} instead) #149190

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9a8dc7e
Replace uses of 'CHECK: br' and 'CHECK-NOT: br' with 'br {{.*}}'.
zachs18 Nov 21, 2025
238ef54
Add tidy check to forbid 'CHECK: br' and 'CHECK-NOT: br' in new codeg…
zachs18 Nov 21, 2025
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6 changes: 6 additions & 0 deletions src/tools/tidy/src/style.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -445,6 +445,7 @@ pub fn check(path: &Path, tidy_ctx: TidyCtx) {
let mut comment_block: Option<(usize, usize)> = None;
let is_test = file.components().any(|c| c.as_os_str() == "tests")
|| file.file_stem().unwrap() == "tests";
let is_codegen_test = is_test && file.components().any(|c| c.as_os_str() == "codegen-llvm");
let is_this_file = file.ends_with(this_file) || this_file.ends_with(file);
let is_test_for_this_file =
is_test && file.parent().unwrap().ends_with(this_file.with_extension(""));
Expand Down Expand Up @@ -488,6 +489,11 @@ pub fn check(path: &Path, tidy_ctx: TidyCtx) {
)
}

if is_codegen_test && trimmed.contains("CHECK") && trimmed.ends_with(": br") {
err("`CHECK: br` and `CHECK-NOT: br` in codegen tests are fragile to false \
positives in mangled symbols. Try using `br {{.*}}` instead.")
}

if !under_rustfmt
&& line.chars().count() > max_columns
&& !long_line_is_ok(&extension, is_error_code, max_columns, line)
Expand Down
12 changes: 6 additions & 6 deletions tests/codegen-llvm/char-ascii-branchless.rs
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Expand Up @@ -7,41 +7,41 @@
// CHECK-LABEL: @is_ascii_alphanumeric_char
#[no_mangle]
pub fn is_ascii_alphanumeric_char(x: char) -> bool {
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
x.is_ascii_alphanumeric()
}

// CHECK-LABEL: @is_ascii_alphanumeric_u8
#[no_mangle]
pub fn is_ascii_alphanumeric_u8(x: u8) -> bool {
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
x.is_ascii_alphanumeric()
}

// CHECK-LABEL: @is_ascii_hexdigit_char
#[no_mangle]
pub fn is_ascii_hexdigit_char(x: char) -> bool {
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
x.is_ascii_hexdigit()
}

// CHECK-LABEL: @is_ascii_hexdigit_u8
#[no_mangle]
pub fn is_ascii_hexdigit_u8(x: u8) -> bool {
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
x.is_ascii_hexdigit()
}

// CHECK-LABEL: @is_ascii_punctuation_char
#[no_mangle]
pub fn is_ascii_punctuation_char(x: char) -> bool {
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
x.is_ascii_punctuation()
}

// CHECK-LABEL: @is_ascii_punctuation_u8
#[no_mangle]
pub fn is_ascii_punctuation_u8(x: u8) -> bool {
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
x.is_ascii_punctuation()
}
2 changes: 1 addition & 1 deletion tests/codegen-llvm/enum/enum-early-otherwise-branch.rs
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Expand Up @@ -12,7 +12,7 @@ pub enum Enum {
pub fn foo(lhs: &Enum, rhs: &Enum) -> bool {
// CHECK-LABEL: define{{.*}}i1 @foo(
// CHECK-NOT: switch
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
// CHECK: [[SELECT:%.*]] = select
// CHECK-NEXT: ret i1 [[SELECT]]
// CHECK-NEXT: }
Expand Down
2 changes: 1 addition & 1 deletion tests/codegen-llvm/issues/cows-dont-have-branches-117763.rs
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Expand Up @@ -9,7 +9,7 @@
// CHECK-LABEL: @branchless_cow_slices
#[no_mangle]
pub fn branchless_cow_slices<'a>(cow: &'a std::borrow::Cow<'a, [u8]>) -> &'a [u8] {
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
// CHECK-NOT: select
// CHECK-NOT: icmp
// CHECK: ret { ptr, {{i32|i64}} }
Expand Down
2 changes: 1 addition & 1 deletion tests/codegen-llvm/issues/issue-107681-unwrap_unchecked.rs
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Expand Up @@ -11,7 +11,7 @@ use std::slice::Iter;
#[no_mangle]
pub unsafe fn foo(x: &mut Copied<Iter<'_, u32>>) -> u32 {
// CHECK-LABEL: @foo(
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
// CHECK-NOT: select
// CHECK: [[RET:%.*]] = load i32, ptr
// CHECK-NEXT: ret i32 [[RET]]
Expand Down
4 changes: 2 additions & 2 deletions tests/codegen-llvm/issues/issue-108395-branchy-bool-match.rs
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Expand Up @@ -6,7 +6,7 @@
// CHECK-LABEL: @wildcard(
#[no_mangle]
pub fn wildcard(a: u16, b: u16, v: u16) -> u16 {
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
match (a == v, b == v) {
(true, false) => 0,
(false, true) => u16::MAX,
Expand All @@ -17,7 +17,7 @@ pub fn wildcard(a: u16, b: u16, v: u16) -> u16 {
// CHECK-LABEL: @exhaustive(
#[no_mangle]
pub fn exhaustive(a: u16, b: u16, v: u16) -> u16 {
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
match (a == v, b == v) {
(true, false) => 0,
(false, true) => u16::MAX,
Expand Down
28 changes: 14 additions & 14 deletions tests/codegen-llvm/issues/issue-119422.rs
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Expand Up @@ -19,65 +19,65 @@ pub fn check_non_null(x: NonNull<u8>) -> bool {
// CHECK-LABEL: @equals_zero_is_false_u8
#[no_mangle]
pub fn equals_zero_is_false_u8(x: NonZero<u8>) -> bool {
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
// CHECK: ret i1 false
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
x.get() == 0
}

// CHECK-LABEL: @not_equals_zero_is_true_u8
#[no_mangle]
pub fn not_equals_zero_is_true_u8(x: NonZero<u8>) -> bool {
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
// CHECK: ret i1 true
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
x.get() != 0
}

// CHECK-LABEL: @equals_zero_is_false_i8
#[no_mangle]
pub fn equals_zero_is_false_i8(x: NonZero<i8>) -> bool {
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
// CHECK: ret i1 false
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
x.get() == 0
}

// CHECK-LABEL: @not_equals_zero_is_true_i8
#[no_mangle]
pub fn not_equals_zero_is_true_i8(x: NonZero<i8>) -> bool {
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
// CHECK: ret i1 true
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
x.get() != 0
}

// CHECK-LABEL: @usize_try_from_u32
#[no_mangle]
pub fn usize_try_from_u32(x: NonZero<u32>) -> NonZero<usize> {
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
// CHECK: zext i32 %{{.*}} to i64
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
// CHECK: ret i64
x.try_into().unwrap()
}

// CHECK-LABEL: @isize_try_from_i32
#[no_mangle]
pub fn isize_try_from_i32(x: NonZero<i32>) -> NonZero<isize> {
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
// CHECK: sext i32 %{{.*}} to i64
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
// CHECK: ret i64
x.try_into().unwrap()
}

// CHECK-LABEL: @u64_from_nonzero_is_not_zero
#[no_mangle]
pub fn u64_from_nonzero_is_not_zero(x: NonZero<u64>) -> bool {
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
// CHECK: ret i1 false
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
let v: u64 = x.into();
v == 0
}
6 changes: 3 additions & 3 deletions tests/codegen-llvm/issues/issue-73258.rs
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Expand Up @@ -18,22 +18,22 @@ pub enum Foo {
pub unsafe fn issue_73258(ptr: *const Foo) -> Foo {
// CHECK-NOT: icmp
// CHECK-NOT: call
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
// CHECK-NOT: select

// CHECK: %[[R:.+]] = load i8
// CHECK-SAME: !range !

// CHECK-NOT: icmp
// CHECK-NOT: call
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
// CHECK-NOT: select

// CHECK: ret i8 %[[R]]

// CHECK-NOT: icmp
// CHECK-NOT: call
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
// CHECK-NOT: select
let k: Option<Foo> = Some(ptr.read());
return k.unwrap();
Expand Down
2 changes: 1 addition & 1 deletion tests/codegen-llvm/issues/num-is-digit-to-digit-59352.rs
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Expand Up @@ -8,7 +8,7 @@
// CHECK-LABEL: @num_to_digit_slow
#[no_mangle]
pub fn num_to_digit_slow(num: char) -> u32 {
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
// CHECK-NOT: panic
if num.is_digit(8) { num.to_digit(8).unwrap() } else { 0 }
}
8 changes: 4 additions & 4 deletions tests/codegen-llvm/iter-repeat-n-trivial-drop.rs
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Expand Up @@ -19,23 +19,23 @@ impl Drop for NotCopy {
// CHECK-LABEL: @iter_repeat_n_next
pub fn iter_repeat_n_next(it: &mut std::iter::RepeatN<NotCopy>) -> Option<NotCopy> {
// CHECK-NEXT: start:
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
// CHECK: %[[COUNT:.+]] = load i64
// CHECK-NEXT: %[[COUNT_ZERO:.+]] = icmp eq i64 %[[COUNT]], 0
// CHECK-NEXT: br i1 %[[COUNT_ZERO]], label %[[EMPTY:.+]], label %[[NOT_EMPTY:.+]]

// CHECK: [[NOT_EMPTY]]:
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
// CHECK: %[[DEC:.+]] = add i64 %[[COUNT]], -1
// CHECK-NEXT: %[[VAL:.+]] = load i16
// CHECK-NEXT: store i64 %[[DEC]]
// CHECK-NEXT: br label %[[EMPTY]]

// CHECK: [[EMPTY]]:
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
// CHECK: phi i16
// CHECK-SAME: [ %[[VAL]], %[[NOT_EMPTY]] ]
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
// CHECK: ret

it.next()
Expand Down
12 changes: 6 additions & 6 deletions tests/codegen-llvm/option-as-slice.rs
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Expand Up @@ -11,14 +11,14 @@ use core::option::Option;
#[no_mangle]
pub fn u64_opt_as_slice(o: &Option<u64>) -> &[u64] {
// CHECK-NOT: select
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
// CHECK-NOT: switch
// CHECK-NOT: icmp
// CHECK: %[[LEN:.+]] = load i64
// CHECK-SAME: !range ![[META_U64:[0-9]+]],
// CHECK-SAME: !noundef
// CHECK-NOT: select
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
// CHECK-NOT: switch
// CHECK-NOT: icmp
// CHECK: %[[T0:.+]] = insertvalue { ptr, i64 } poison, ptr %{{.+}}, 0
Expand All @@ -31,13 +31,13 @@ pub fn u64_opt_as_slice(o: &Option<u64>) -> &[u64] {
#[no_mangle]
pub fn nonzero_u64_opt_as_slice(o: &Option<NonZero<u64>>) -> &[NonZero<u64>] {
// CHECK-NOT: select
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
// CHECK-NOT: switch
// CHECK-NOT: icmp
// CHECK: %[[NZ:.+]] = icmp ne i64 %{{.+}}, 0
// CHECK-NEXT: %[[LEN:.+]] = zext i1 %[[NZ]] to i64
// CHECK-NOT: select
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
// CHECK-NOT: switch
// CHECK-NOT: icmp
// CHECK: %[[T0:.+]] = insertvalue { ptr, i64 } poison, ptr %o, 0
Expand All @@ -50,15 +50,15 @@ pub fn nonzero_u64_opt_as_slice(o: &Option<NonZero<u64>>) -> &[NonZero<u64>] {
#[no_mangle]
pub fn u8_opt_as_slice(o: &Option<u8>) -> &[u8] {
// CHECK-NOT: select
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
// CHECK-NOT: switch
// CHECK-NOT: icmp
// CHECK: %[[TAG:.+]] = load i8
// CHECK-SAME: !range ![[META_U8:[0-9]+]],
// CHECK-SAME: !noundef
// CHECK: %[[LEN:.+]] = zext{{.*}} i8 %[[TAG]] to i64
// CHECK-NOT: select
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
// CHECK-NOT: switch
// CHECK-NOT: icmp
// CHECK: %[[T0:.+]] = insertvalue { ptr, i64 } poison, ptr %{{.+}}, 0
Expand Down
2 changes: 1 addition & 1 deletion tests/codegen-llvm/slice-init.rs
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Expand Up @@ -69,7 +69,7 @@ const N: usize = 100;
#[no_mangle]
pub fn u16_init_one_bytes() -> [u16; N] {
// CHECK-NOT: select
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
// CHECK-NOT: switch
// CHECK-NOT: icmp
// CHECK: call void @llvm.memset.p0
Expand Down
2 changes: 1 addition & 1 deletion tests/codegen-llvm/slice-iter-fold.rs
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Expand Up @@ -5,7 +5,7 @@
#[no_mangle]
pub fn slice_fold_to_last(slice: &[i32]) -> Option<&i32> {
// CHECK-NOT: loop
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
// CHECK-NOT: call
// CHECK: ret
slice.iter().fold(None, |_, i| Some(i))
Expand Down
24 changes: 12 additions & 12 deletions tests/codegen-llvm/vecdeque-drain.rs
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Expand Up @@ -10,7 +10,7 @@ use std::collections::VecDeque;

// CHECK-LABEL: @clear
// CHECK-NOT: call
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
// CHECK: getelementptr inbounds
// CHECK-NEXT: {{call void @llvm.memset|store}}
// CHECK-NEXT: ret void
Expand All @@ -21,15 +21,15 @@ pub fn clear(v: &mut VecDeque<i32>) {

// CHECK-LABEL: @truncate
// CHECK-NOT: call
// CHECK: br
// CHECK: br {{.*}}
// CHECK-NOT: call
// CHECK: br
// CHECK: br {{.*}}
// CHECK-NOT: call
// CHECK: br
// CHECK: br {{.*}}
// CHECK-NOT: call
// CHECK: br
// CHECK: br {{.*}}
// CHECK-NOT: call
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
// CHECK: ret void
#[no_mangle]
pub fn truncate(v: &mut VecDeque<i32>, n: usize) {
Expand All @@ -40,17 +40,17 @@ pub fn truncate(v: &mut VecDeque<i32>, n: usize) {

// CHECK-LABEL: @advance
// CHECK-NOT: call
// CHECK: br
// CHECK: br {{.*}}
// CHECK-NOT: call
// CHECK: br
// CHECK: br {{.*}}
// CHECK-NOT: call
// CHECK: br
// CHECK: br {{.*}}
// CHECK-NOT: call
// CHECK: br
// CHECK: br {{.*}}
// CHECK-NOT: call
// CHECK: br
// CHECK: br {{.*}}
// CHECK-NOT: call
// CHECK-NOT: br
// CHECK-NOT: br {{.*}}
// CHECK: ret void
#[no_mangle]
pub fn advance(v: &mut VecDeque<i32>, n: usize) {
Expand Down
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