Don't use usub.with.overflow intrinsic

compiler/rustc_codegen_llvm/src/builder.rs

@@ -365,11 +365,14 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
                 Int(I64) => "llvm.ssub.with.overflow.i64",
                 Int(I128) => "llvm.ssub.with.overflow.i128",
 
-                Uint(U8) => "llvm.usub.with.overflow.i8",
-                Uint(U16) => "llvm.usub.with.overflow.i16",
-                Uint(U32) => "llvm.usub.with.overflow.i32",
-                Uint(U64) => "llvm.usub.with.overflow.i64",
-                Uint(U128) => "llvm.usub.with.overflow.i128",
+                Uint(_) => {
+                    // Emit sub and icmp instead of llvm.usub.with.overflow. LLVM considers these
+                    // to be the canonical form. It will attempt to reform llvm.usub.with.overflow
+                    // in the backend if profitable.
+                    let sub = self.sub(lhs, rhs);
+                    let cmp = self.icmp(IntPredicate::IntULT, lhs, rhs);
+                    return (sub, cmp);
+                }
 
                 _ => unreachable!(),
             },

src/test/codegen/issue-103285-ptr-addr-overflow-check.rs

@@ -0,0 +1,16 @@
+// compile-flags: -O -C debug-assertions=yes
+
+#![crate_type = "lib"]
+#![feature(strict_provenance)]
+
+#[no_mangle]
+pub fn test(src: *const u8, dst: *const u8) -> usize {
+    // CHECK-LABEL: @test(
+    // CHECK-NOT: panic
+    let src_usize = src.addr();
+    let dst_usize = dst.addr();
+    if src_usize > dst_usize {
+        return src_usize - dst_usize;
+    }
+    return 0;
+}