1 files changed, 161 insertions, 0 deletions
diff --git a/tests/codegen-llvm/vec-in-place.rs b/tests/codegen-llvm/vec-in-place.rs
new file mode 100644
index 00000000000..a5ef8653b99
--- /dev/null
+++ b/tests/codegen-llvm/vec-in-place.rs
@@ -0,0 +1,161 @@
+//@ ignore-std-debug-assertions (FIXME: checks for call detect scoped noalias metadata)
+//@ compile-flags: -Copt-level=3 -Z merge-functions=disabled
+#![crate_type = "lib"]
+
+// Ensure that trivial casts of vec elements are O(1)
+
+pub struct Wrapper<T>(T);
+
+// previously repr(C) caused the optimization to fail
+#[repr(C)]
+pub struct Foo {
+    a: u64,
+    b: u64,
+    c: u64,
+    d: u64,
+}
+
+// implementing Copy exercises the TrustedRandomAccess specialization inside the in-place
+// specialization
+#[derive(Copy, Clone)]
+pub struct Bar {
+    a: u64,
+    b: u64,
+    c: u64,
+    d: u64,
+}
+
+// this exercises the try-fold codepath
+pub struct Baz {
+    a: u64,
+    b: u64,
+    c: u64,
+    d: u64,
+}
+
+// CHECK-LABEL: @vec_iterator_cast_primitive
+#[no_mangle]
+pub fn vec_iterator_cast_primitive(vec: Vec<i8>) -> Vec<u8> {
+    // CHECK-NOT: loop
+    // CHECK-NOT: call
+    // CHECK: call{{.+}}void @llvm.assume(i1 %{{.+}})
+    // CHECK-NOT: loop
+    // CHECK-NOT: call
+    vec.into_iter().map(|e| e as u8).collect()
+}
+
+// CHECK-LABEL: @vec_iterator_cast_wrapper
+#[no_mangle]
+pub fn vec_iterator_cast_wrapper(vec: Vec<u8>) -> Vec<Wrapper<u8>> {
+    // CHECK-NOT: loop
+    // CHECK-NOT: call
+    // CHECK: call{{.+}}void @llvm.assume(i1 %{{.+}})
+    // CHECK-NOT: loop
+    // CHECK-NOT: call
+    vec.into_iter().map(|e| Wrapper(e)).collect()
+}
+
+// CHECK-LABEL: @vec_iterator_cast_signed
+#[no_mangle]
+pub fn vec_iterator_cast_signed(vec: Vec<i32>) -> Vec<u32> {
+    // CHECK-NOT: and i{{[0-9]+}} %{{.*}}, {{[0-9]+}}
+    vec.into_iter().map(|e| u32::from_ne_bytes(e.to_ne_bytes())).collect()
+}
+
+// CHECK-LABEL: @vec_iterator_cast_signed_nested
+#[no_mangle]
+pub fn vec_iterator_cast_signed_nested(vec: Vec<Vec<i32>>) -> Vec<Vec<u32>> {
+    // CHECK-NOT: br i1 %{{.*}}, label %{{.*}}, label %{{.*}}
+    // CHECK-NOT: %{{.*}} = udiv
+    vec.into_iter()
+        .map(|e| e.into_iter().map(|e| u32::from_ne_bytes(e.to_ne_bytes())).collect())
+        .collect()
+}
+
+// CHECK-LABEL: @vec_iterator_cast_unwrap
+#[no_mangle]
+pub fn vec_iterator_cast_unwrap(vec: Vec<Wrapper<u8>>) -> Vec<u8> {
+    // CHECK-NOT: loop
+    // CHECK-NOT: call
+    // CHECK: call{{.+}}void @llvm.assume(i1 %{{.+}})
+    // CHECK-NOT: loop
+    // CHECK-NOT: call
+    vec.into_iter().map(|e| e.0).collect()
+}
+
+// CHECK-LABEL: @vec_iterator_cast_aggregate
+#[no_mangle]
+pub fn vec_iterator_cast_aggregate(vec: Vec<[u64; 4]>) -> Vec<Foo> {
+    // CHECK-NOT: loop
+    // CHECK-NOT: call
+    // CHECK: call{{.+}}void @llvm.assume(i1 %{{.+}})
+    // CHECK-NOT: loop
+    // CHECK-NOT: call
+    vec.into_iter().map(|e| unsafe { std::mem::transmute(e) }).collect()
+}
+
+// CHECK-LABEL: @vec_iterator_cast_deaggregate_tra
+#[no_mangle]
+pub fn vec_iterator_cast_deaggregate_tra(vec: Vec<Bar>) -> Vec<[u64; 4]> {
+    // CHECK-NOT: loop
+    // CHECK-NOT: call
+    // CHECK: call{{.+}}void @llvm.assume(i1 %{{.+}})
+    // CHECK-NOT: loop
+    // CHECK-NOT: call
+
+    // Safety: For the purpose of this test we assume that Bar layout matches [u64; 4].
+    // This currently is not guaranteed for repr(Rust) types, but it happens to work here and
+    // the UCG may add additional guarantees for homogenous types in the future that would make this
+    // correct.
+    vec.into_iter().map(|e| unsafe { std::mem::transmute(e) }).collect()
+}
+
+// CHECK-LABEL: @vec_iterator_cast_deaggregate_fold
+#[no_mangle]
+pub fn vec_iterator_cast_deaggregate_fold(vec: Vec<Baz>) -> Vec<[u64; 4]> {
+    // CHECK-NOT: loop
+    // CHECK-NOT: call
+    // CHECK: call{{.+}}void @llvm.assume(i1 %{{.+}})
+    // CHECK-NOT: loop
+    // CHECK-NOT: call
+
+    // Safety: For the purpose of this test we assume that Bar layout matches [u64; 4].
+    // This currently is not guaranteed for repr(Rust) types, but it happens to work here and
+    // the UCG may add additional guarantees for homogenous types in the future that would make this
+    // correct.
+    vec.into_iter().map(|e| unsafe { std::mem::transmute(e) }).collect()
+}
+
+// CHECK-LABEL: @vec_iterator_cast_unwrap_drop
+#[no_mangle]
+pub fn vec_iterator_cast_unwrap_drop(vec: Vec<Wrapper<String>>) -> Vec<String> {
+    // CHECK-NOT: br i1 %{{.*}}, label %{{.*}}, label %{{.*}}
+    // CHECK-NOT: %{{.*}} = mul
+    // CHECK-NOT: %{{.*}} = udiv
+    // CHECK: call
+    // CHECK-SAME: void @llvm.assume(i1 %{{.+}})
+    // CHECK-NOT: br i1 %{{.*}}, label %{{.*}}, label %{{.*}}
+    // CHECK-NOT: call
+    // CHECK-NOT: %{{.*}} = mul
+    // CHECK-NOT: %{{.*}} = udiv
+    // CHECK: ret void
+
+    vec.into_iter().map(|Wrapper(e)| e).collect()
+}
+
+// CHECK-LABEL: @vec_iterator_cast_wrap_drop
+#[no_mangle]
+pub fn vec_iterator_cast_wrap_drop(vec: Vec<String>) -> Vec<Wrapper<String>> {
+    // CHECK-NOT: br i1 %{{.*}}, label %{{.*}}, label %{{.*}}
+    // CHECK-NOT: %{{.*}} = mul
+    // CHECK-NOT: %{{.*}} = udiv
+    // CHECK: call
+    // CHECK-SAME: void @llvm.assume(i1 %{{.+}})
+    // CHECK-NOT: br i1 %{{.*}}, label %{{.*}}, label %{{.*}}
+    // CHECK-NOT: call
+    // CHECK-NOT: %{{.*}} = mul
+    // CHECK-NOT: %{{.*}} = udiv
+    // CHECK: ret void
+
+    vec.into_iter().map(Wrapper).collect()
+}