Auto merge of #101395 - saethlin:strict-provenance-codegen, r=nikic

Add a codegen test for #96152

This is a regression test for #96152, it is intended to check that our codegen for a particular strict provenance pattern is always as good as the ptr2int2ptr/provenance-ignoring style.

r? `@nikic`

src/test/assembly/strict_provenance.rs

@@ -0,0 +1,37 @@
+// assembly-output: emit-asm
+// compile-flags: -Copt-level=1
+// only-x86_64
+// min-llvm-version: 15.0
+#![crate_type = "rlib"]
+
+// CHECK-LABEL: old_style
+// CHECK: movq %{{.*}}, %rax
+// CHECK: orq $1, %rax
+// CHECK: retq
+#[no_mangle]
+pub fn old_style(a: *mut u8) -> *mut u8 {
+    (a as usize | 1) as *mut u8
+}
+
+// CHECK-LABEL: cheri_compat
+// CHECK: movq %{{.*}}, %rax
+// CHECK: orq $1, %rax
+// CHECK: retq
+#[no_mangle]
+pub fn cheri_compat(a: *mut u8) -> *mut u8 {
+    let old = a as usize;
+    let new = old | 1;
+    let diff = new.wrapping_sub(old);
+    a.wrapping_add(diff)
+}
+
+// CHECK-LABEL: definitely_not_a_null_pointer
+// CHECK: movq %{{.*}}, %rax
+// CHECK: orq $1, %rax
+// CHECK: retq
+#[no_mangle]
+pub fn definitely_not_a_null_pointer(a: *mut u8) -> *mut u8 {
+    let old = a as usize;
+    let new = old | 1;
+    a.wrapping_sub(old).wrapping_add(new)
+}