Add a simple simplify-cfg optimization for assembly

sway-core/src/asm_generation/fuel/abstract_instruction_set.rs

@@ -27,6 +27,7 @@ impl AbstractInstructionSet {
     pub(crate) fn optimize(self, data_section: &DataSection) -> AbstractInstructionSet {
         self.const_indexing_aggregates_function(data_section)
             .dce()
+            .simplify_cfg()
             .remove_sequential_jumps()
             .remove_redundant_moves()
             .remove_unused_ops()

sway-core/src/asm_generation/fuel/optimizations.rs

@@ -1,11 +1,11 @@
-use std::collections::BTreeSet;
+use std::collections::{BTreeSet, HashMap};
 
 use either::Either;
 use rustc_hash::{FxHashMap, FxHashSet};
 
 use crate::{
     asm_generation::fuel::compiler_constants,
-    asm_lang::{ControlFlowOp, VirtualImmediate12, VirtualOp, VirtualRegister},
+    asm_lang::{ControlFlowOp, Label, VirtualImmediate12, VirtualOp, VirtualRegister},
 };
 
 use super::{
@@ -269,4 +269,44 @@ impl AbstractInstructionSet {
 
         self
     }
+
+    // Remove unreachable instructions.
+    pub(crate) fn simplify_cfg(mut self) -> AbstractInstructionSet {
+        let ops = &self.ops;
+
+        if ops.is_empty() {
+            return self;
+        }
+
+        // Keep track of a map between jump labels and op indices. Useful to compute op successors.
+        let mut label_to_index: HashMap<Label, usize> = HashMap::default();
+        for (idx, op) in ops.iter().enumerate() {
+            if let Either::Right(ControlFlowOp::Label(op_label)) = op.opcode {
+                label_to_index.insert(op_label, idx);
+            }
+        }
+
+        let mut reachables = vec![false; ops.len()];
+        let mut worklist = vec![0];
+        while let Some(op_idx) = worklist.pop() {
+            assert!(!reachables[op_idx]);
+            reachables[op_idx] = true;
+            let op = &ops[op_idx];
+            for s in &op.successors(op_idx, ops, &label_to_index) {
+                if !reachables[*s] {
+                    worklist.push(*s);
+                }
+            }
+        }
+
+        let reachable_ops = self
+            .ops
+            .into_iter()
+            .enumerate()
+            .filter_map(|(idx, op)| if reachables[idx] { Some(op) } else { None })
+            .collect();
+        self.ops = reachable_ops;
+
+        self
+    }
 }

test/src/e2e_vm_tests/test_programs/should_pass/language/abort_control_flow_good/test.toml

@@ -1,4 +1,4 @@
-category = "disabled" # TODO: Enable once https://github.com/FuelLabs/sway/issues/6174 is fixed.
+category = "run"
 expected_result = { action = "revert", value = 42 }
 expected_result_new_encoding = { action = "revert", value = 42 }
 validate_abi = true

test/src/e2e_vm_tests/test_programs/should_pass/language/break_and_continue_block_ret/test.toml

@@ -1,3 +1,3 @@
-category = "disabled" # TODO: Enable once https://github.com/FuelLabs/sway/issues/6174 is fixed.
+category = "compile"
 
 # not: $()This returns a value of type unknown, which is not assigned to anything and is ignored.