Add invariant to Vec::pop that len < cap if pop successful

Fixes: https://github.com/rust-lang/rust/issues/114334

1 files changed, 24 insertions, 0 deletions

diff --git a/tests/codegen/vec_pop_push_noop.rs b/tests/codegen/vec_pop_push_noop.rs
new file mode 100644
index 00000000000..8bc7b68a816
--- /dev/null
+++ b/tests/codegen/vec_pop_push_noop.rs
@@ -0,0 +1,24 @@
+// compile-flags: -O
+
+#![crate_type = "lib"]
+
+#[no_mangle]
+// CHECK-LABEL: @noop(
+pub fn noop(v: &mut Vec<u8>) {
+    // CHECK-NOT: reserve_for_push
+    // CHECK-NOT: call
+    // CHECK: tail call void @llvm.assume
+    // CHECK-NOT: reserve_for_push
+    // CHECK-NOT: call
+    // CHECK: ret
+    if let Some(x) = v.pop() {
+        v.push(x)
+    }
+}
+
+#[no_mangle]
+// CHECK-LABEL: @push_byte(
+pub fn push_byte(v: &mut Vec<u8>) {
+    // CHECK: call {{.*}}reserve_for_push
+    v.push(3);
+}