Iterator (https://github.com/Shopify/ruby/pull/372)

* Iterator

* Use the new iterator for the X86 backend split

* Use iterator for reg alloc, remove forward pass

* Fix up iterator usage on AArch64

* Update yjit/src/backend/ir.rs

Co-authored-by: Maxime Chevalier-Boisvert <maximechevalierb@gmail.com>

* Various PR feedback for iterators for IR

* Use a local mutable reference for a64_split

* Move tests from ir.rs to tests.rs in backend

* Fix x86 shift instructions live range calculation

* Iterator

* Use the new iterator for the X86 backend split

* Fix up x86 iterator usage

* Fix ARM iterator usage

* Remove unintentionally duplicated tests

1 files changed, 38 insertions, 0 deletions

diff --git a/yjit/src/backend/tests.rs b/yjit/src/backend/tests.rs
index a31e16071b..e4ab95d4ee 100644
--- a/yjit/src/backend/tests.rs
+++ b/yjit/src/backend/tests.rs
@@ -299,3 +299,41 @@ fn test_bake_string() {
     asm.bake_string("Hello, world!");
     asm.compile_with_num_regs(&mut cb, 0);
 }
+
+#[test]
+fn test_draining_iterator() {
+    let mut asm = Assembler::new();
+
+    asm.load(Opnd::None);
+    asm.store(Opnd::None, Opnd::None);
+    asm.add(Opnd::None, Opnd::None);
+
+    let mut iter = asm.into_draining_iter();
+
+    while let Some((index, insn)) = iter.next_unmapped() {
+        match index {
+            0 => assert_eq!(insn.op, Op::Load),
+            1 => assert_eq!(insn.op, Op::Store),
+            2 => assert_eq!(insn.op, Op::Add),
+            _ => panic!("Unexpected instruction index"),
+        };
+    }
+}
+
+#[test]
+fn test_lookback_iterator() {
+    let mut asm = Assembler::new();
+
+    asm.load(Opnd::None);
+    asm.store(Opnd::None, Opnd::None);
+    asm.store(Opnd::None, Opnd::None);
+
+    let mut iter = asm.into_lookback_iter();
+
+    while let Some((index, insn)) = iter.next_unmapped() {
+        if index > 0 {
+            assert_eq!(iter.get_previous().unwrap().opnds[0], Opnd::None);
+            assert_eq!(insn.op, Op::Store);
+        }
+    }
+}