Auto merge of #135760 - scottmcm:disjoint-bitor, r=WaffleLapkin

Add `unchecked_disjoint_bitor` per ACP373

Following the names from libs-api in https://github.com/rust-lang/libs-team/issues/373#issuecomment-2085686057

Includes a fallback implementation so this doesn't have to update cg_clif or cg_gcc, and overrides it in cg_llvm to use `or disjoint`, which [is available in LLVM 18](https://releases.llvm.org/18.1.0/docs/LangRef.html#or-instruction) so hopefully we don't need any version checks.

2 files changed, 43 insertions, 0 deletions

diff --git a/tests/codegen/bigint-helpers.rs b/tests/codegen/bigint-helpers.rs
new file mode 100644
index 00000000000..355cccb8150
--- /dev/null
+++ b/tests/codegen/bigint-helpers.rs
@@ -0,0 +1,13 @@
+//@ compile-flags: -C opt-level=3
+
+#![crate_type = "lib"]
+#![feature(bigint_helper_methods)]
+
+// CHECK-LABEL: @u32_carrying_add
+#[no_mangle]
+pub fn u32_carrying_add(a: u32, b: u32, c: bool) -> (u32, bool) {
+    // CHECK: @llvm.uadd.with.overflow.i32
+    // CHECK: @llvm.uadd.with.overflow.i32
+    // CHECK: or disjoint i1
+    u32::carrying_add(a, b, c)
+}
diff --git a/tests/codegen/intrinsics/disjoint_bitor.rs b/tests/codegen/intrinsics/disjoint_bitor.rs
new file mode 100644
index 00000000000..fc45439ee0b
--- /dev/null
+++ b/tests/codegen/intrinsics/disjoint_bitor.rs
@@ -0,0 +1,30 @@
+//@ compile-flags: -C no-prepopulate-passes -Z mir-opt-level=0
+
+#![crate_type = "lib"]
+#![feature(core_intrinsics)]
+
+use std::intrinsics::disjoint_bitor;
+
+// CHECK-LABEL: @disjoint_bitor_signed
+#[no_mangle]
+pub unsafe fn disjoint_bitor_signed(x: i32, y: i32) -> i32 {
+    // CHECK: or disjoint i32 %x, %y
+    disjoint_bitor(x, y)
+}
+
+// CHECK-LABEL: @disjoint_bitor_unsigned
+#[no_mangle]
+pub unsafe fn disjoint_bitor_unsigned(x: u64, y: u64) -> u64 {
+    // CHECK: or disjoint i64 %x, %y
+    disjoint_bitor(x, y)
+}
+
+// CHECK-LABEL: @disjoint_bitor_literal
+#[no_mangle]
+pub unsafe fn disjoint_bitor_literal() -> u8 {
+    // This is a separate check because even without any passes,
+    // LLVM will fold so it's not an instruction, which can assert in LLVM.
+
+    // CHECK: store i8 3
+    disjoint_bitor(1, 2)
+}