[compiler-v2] Add loop labels to the language

Besides the user being able to describe more complex algorithms more efficiently, loop labels are required to express any reducible control flow in the AST language, and create parity of the AST with the bytecode level for this kind of code (which is also what can be generated from Move).

third_party/move/move-compiler-v2/src/bytecode_generator.rs

@@ -447,11 +447,11 @@ impl<'env> Generator<'env> {
                 self.emit_with(*id, |attr| Bytecode::Jump(attr, continue_label));
                 self.emit_with(*id, |attr| Bytecode::Label(attr, break_label));
             },
-            ExpData::LoopCont(id, 0, do_continue) => {
+            ExpData::LoopCont(id, nest, do_continue) => {
                 if let Some(LoopContext {
                     continue_label,
                     break_label,
-                }) = self.loops.last()
+                }) = self.loops.iter().rev().nth(*nest)
                 {
                     let target = if *do_continue {
                         *continue_label
@@ -463,9 +463,6 @@ impl<'env> Generator<'env> {
                     self.error(*id, "missing enclosing loop statement")
                 }
             },
-            ExpData::LoopCont(_, _, _) => {
-                unimplemented!("continue/break with nesting")
-            },
             ExpData::SpecBlock(id, spec) => {
                 // Map locals in spec to assigned temporaries.
                 let mut replacer = |id, target| {

third_party/move/move-compiler-v2/tests/bytecode-generator/loop_labels.exp

@@ -0,0 +1,78 @@
+// -- Model dump before bytecode pipeline
+module 0x815::test {
+    private fun f1() {
+        loop {
+          loop {
+            loop {
+              if true {
+                loop {
+                  if false {
+                    continue[3]
+                  } else {
+                    break[1]
+                  };
+                  break
+                }
+              } else {
+                continue[2]
+              }
+            }
+          };
+          break
+        }
+    }
+} // end 0x815::test
+
+// -- Sourcified model before bytecode pipeline
+module 0x815::test {
+    fun f1() {
+        'l0: loop {
+            loop 'l1: loop if (true) loop {
+                if (false) continue 'l0 else break 'l1;
+                break
+            } else continue 'l0;
+            break
+        }
+    }
+}
+
+============ initial bytecode ================
+
+[variant baseline]
+fun test::f1() {
+     var $t0: bool
+     var $t1: bool
+  0: label L0
+  1: label L2
+  2: label L4
+  3: $t0 := true
+  4: if ($t0) goto 5 else goto 19
+  5: label L6
+  6: label L9
+  7: $t1 := false
+  8: if ($t1) goto 9 else goto 12
+  9: label L11
+ 10: goto 0
+ 11: goto 14
+ 12: label L12
+ 13: goto 23
+ 14: label L13
+ 15: goto 17
+ 16: goto 6
+ 17: label L10
+ 18: goto 21
+ 19: label L7
+ 20: goto 0
+ 21: label L8
+ 22: goto 2
+ 23: label L5
+ 24: goto 1
+ 25: label L3
+ 26: goto 28
+ 27: goto 0
+ 28: label L1
+ 29: return ()
+}
+
+
+============ bytecode verification succeeded ========

third_party/move/move-compiler-v2/tests/bytecode-generator/loop_labels.move

@@ -0,0 +1,14 @@
+module 0x815::test {
+    fun f1() {
+        'outer: loop {
+            // unlabeled loop, but counts in nesting in AST
+            loop {
+                'inner: loop if (true) loop {
+                    if (false) continue 'outer else break 'inner;
+                    break
+                } else continue 'outer
+            };
+            break
+        }
+    }
+}

third_party/move/move-compiler-v2/tests/checking-lang-v1/loop_labels.exp

@@ -0,0 +1,31 @@
+
+Diagnostics:
+error: unsupported language construct
+  ┌─ tests/checking-lang-v1/loop_labels.move:3:9
+  │
+3 │         'outer: loop {
+  │         ^^^^^^ Move language construct `'outer` is not enabled until version 2.1
+
+error: unsupported language construct
+  ┌─ tests/checking-lang-v1/loop_labels.move:6:17
+  │
+6 │                 'inner: loop if (true) loop {
+  │                 ^^^^^^ Move language construct `'inner` is not enabled until version 2.1
+
+error: unsupported language construct
+  ┌─ tests/checking-lang-v1/loop_labels.move:7:41
+  │
+7 │                     if (false) continue 'outer else break 'inner;
+  │                                         ^^^^^^ Move language construct `'outer` is not enabled until version 2.1
+
+error: unsupported language construct
+  ┌─ tests/checking-lang-v1/loop_labels.move:7:59
+  │
+7 │                     if (false) continue 'outer else break 'inner;
+  │                                                           ^^^^^^ Move language construct `'inner` is not enabled until version 2.1
+
+error: unsupported language construct
+  ┌─ tests/checking-lang-v1/loop_labels.move:9:33
+  │
+9 │                 } else continue 'outer
+  │                                 ^^^^^^ Move language construct `'outer` is not enabled until version 2.1

third_party/move/move-compiler-v2/tests/checking-lang-v1/loop_labels.move

@@ -0,0 +1,14 @@
+module 0x815::test {
+    fun f1() {
+        'outer: loop {
+            // unlabeled loop, but counts in nesting in AST
+            loop {
+                'inner: loop if (true) loop {
+                    if (false) continue 'outer else break 'inner;
+                    break
+                } else continue 'outer
+            };
+            break
+        }
+    }
+}

third_party/move/move-compiler-v2/tests/checking/control_flow/loop_labels_check_err.exp

@@ -0,0 +1,21 @@
+
+Diagnostics:
+error: label `'outer` undefined
+  ┌─ tests/checking/control_flow/loop_labels_check_err.move:3:15
+  │
+3 │         break 'outer;
+  │               ^^^^^^
+
+error: label `'inner` undefined
+  ┌─ tests/checking/control_flow/loop_labels_check_err.move:5:19
+  │
+5 │             break 'inner
+  │                   ^^^^^^
+
+error: label `'l1` already used by outer loop
+   ┌─ tests/checking/control_flow/loop_labels_check_err.move:11:19
+   │
+11 │         'l1: loop 'l1: loop {};
+   │         ---       ^^^
+   │         │
+   │         outer definition of label

third_party/move/move-compiler-v2/tests/checking/control_flow/loop_labels_check_err.move

@@ -0,0 +1,14 @@
+module 0x815::test {
+    fun undefined_label() {
+        break 'outer;
+        'outer: loop {
+            break 'inner
+        }
+    }
+
+    fun duplicate_label() {
+        'l1: loop {};
+        'l1: loop 'l1: loop {};
+        'l1: loop {}
+    }
+}

third_party/move/move-compiler-v2/tests/checking/control_flow/loop_labels_check_ok.exp

@@ -0,0 +1,37 @@
+// -- Model dump before bytecode pipeline
+module 0x815::test {
+    private fun f1() {
+        loop {
+          loop {
+            loop {
+              if true {
+                loop {
+                  if false {
+                    continue[3]
+                  } else {
+                    break[1]
+                  };
+                  break
+                }
+              } else {
+                continue[2]
+              }
+            }
+          };
+          break
+        }
+    }
+} // end 0x815::test
+
+// -- Sourcified model before bytecode pipeline
+module 0x815::test {
+    fun f1() {
+        'l0: loop {
+            loop 'l1: loop if (true) loop {
+                if (false) continue 'l0 else break 'l1;
+                break
+            } else continue 'l0;
+            break
+        }
+    }
+}

third_party/move/move-compiler-v2/tests/checking/control_flow/loop_labels_check_ok.move

@@ -0,0 +1,14 @@
+module 0x815::test {
+    fun f1() {
+        'outer: loop {
+            // unlabeled loop, but counts in nesting in AST
+            loop {
+                'inner: loop if (true) loop {
+                    if (false) continue 'outer else break 'inner;
+                    break
+                } else continue 'outer
+            };
+            break
+        }
+    }
+}

third_party/move/move-compiler-v2/tests/checking/control_flow/loop_labels_parse_err1.exp

@@ -0,0 +1,10 @@
+
+Diagnostics:
+error: unexpected token
+  ┌─ tests/checking/control_flow/loop_labels_parse_err1.move:3:13
+  │
+3 │         'a: if (true) false else true
+  │             ^^
+  │             │
+  │             Unexpected 'if'
+  │             Expected one of: 'while' or 'loop'

third_party/move/move-compiler-v2/tests/checking/control_flow/loop_labels_parse_err1.move

@@ -0,0 +1,5 @@
+module 0x815::test {
+    fun f1(): bool {
+        'a: if (true) false else true
+    }
+}

third_party/move/move-compiler-v2/tests/checking/control_flow/loop_labels_parse_err2.exp

@@ -0,0 +1,10 @@
+
+Diagnostics:
+error: unexpected token
+  ┌─ tests/checking/control_flow/loop_labels_parse_err2.move:3:13
+  │
+3 │         'a: if (true) false else true
+  │             ^^
+  │             │
+  │             Unexpected 'if'
+  │             Expected one of: 'while' or 'loop'

third_party/move/move-compiler-v2/tests/checking/control_flow/loop_labels_parse_err2.move

@@ -0,0 +1,5 @@
+module 0x815::test {
+    fun f1(): bool {
+        'a: if (true) false else true
+    }
+}

third_party/move/move-compiler-v2/tests/testsuite.rs

@@ -106,7 +106,7 @@ const TEST_CONFIGS: Lazy<BTreeMap<&str, TestConfig>> = Lazy::new(|| {
         // Turn optimization on by default. Some configs below may turn it off.
         .set_experiment(Experiment::OPTIMIZE, true)
         .set_experiment(Experiment::OPTIMIZE_WAITING_FOR_COMPARE_TESTS, true)
-        .set_language_version(LanguageVersion::V2_0);
+        .set_language_version(LanguageVersion::V2_1);
     opts.testing = true;
     let configs = vec![
         // --- Tests for checking and ast processing
@@ -723,7 +723,7 @@ const TEST_CONFIGS: Lazy<BTreeMap<&str, TestConfig>> = Lazy::new(|| {
             include: vec!["/op-equal/"],
             exclude: vec![],
             exp_suffix: None,
-            options: opts.clone().set_language_version(LanguageVersion::V2_1),
+            options: opts.clone(),
             // Run the entire compiler pipeline to double-check the result
             stop_after: StopAfter::FileFormat,
             dump_ast: DumpLevel::EndStage,

third_party/move/move-compiler-v2/transactional-tests/tests/no-v1-comparison/loop_labels.exp

@@ -0,0 +1 @@
+processed 1 task

third_party/move/move-compiler-v2/transactional-tests/tests/no-v1-comparison/loop_labels.move

@@ -0,0 +1,18 @@
+//# run
+script {
+    fun main() {
+        let result = 0;
+        'outer: while (result < 100) {
+            while (result < 50) {
+                'inner: while (result < 30) {
+                    result += 1;
+                    continue 'outer
+               };
+               result += 10;
+               continue 'outer
+            };
+            result += 20
+        };
+        assert!(result == 110);
+    }
+}