Merge 580928b into 2303615

compiler/noirc_evaluator/src/ssa/ir/cfg.rs

@@ -59,7 +59,7 @@ impl ControlFlowGraph {
 
  /// Clears out a given block's successors. This also removes the given block from
  /// being a predecessor of any of its previous successors.
- fn invalidate_block_successors(&mut self, basic_block_id: BasicBlockId) {
+ pub(crate) fn invalidate_block_successors(&mut self, basic_block_id: BasicBlockId) {
  let node = self
  .data
  .get_mut(&basic_block_id)

compiler/noirc_evaluator/src/ssa/opt/simplify_cfg.rs

@@ -60,7 +60,6 @@ impl Function {
  check_for_constant_jmpif(self, block, &mut cfg);
 
  let mut predecessors = cfg.predecessors(block);
-
  if predecessors.len() == 1 {
  let predecessor =
  predecessors.next().expect("Already checked length of predecessors");
@@ -99,14 +98,23 @@ fn check_for_constant_jmpif(
  }) = function.dfg[block].terminator()
  {
  if let Some(constant) = function.dfg.get_numeric_constant(*condition) {
- let destination =
- if constant.is_zero() { *else_destination } else { *then_destination };
+ let (destination, unchosen_destination) = if constant.is_zero() {
+ (*else_destination, *then_destination)
+ } else {
+ (*then_destination, *else_destination)
+ };
 
  let arguments = Vec::new();
  let call_stack = call_stack.clone();
  let jmp = TerminatorInstruction::Jmp { destination, arguments, call_stack };
  function.dfg[block].set_terminator(jmp);
  cfg.recompute_block(function, block);
+
+ // If `block` was the only predecessor to `unchosen_destination` then it's no long reachable through the CFG,
+ // we can then invalidate it successors as it's an invalid predecessor.
+ if cfg.predecessors(unchosen_destination).len() == 0 {
+ cfg.invalidate_block_successors(unchosen_destination);
+ }
  }
  }
 }