Costs: Increase cost of casts (#4661)

Casts involve branches in the VM, so adding a cast in return for removing a branch
(like If=>Select) is not beneficial. We don't want to ever do any more casts than we
already are.

1 files changed, 3 insertions, 0 deletions

diff --git a/src/passes/RemoveUnusedBrs.cpp b/src/passes/RemoveUnusedBrs.cpp
index f383f669a..3c4723c7f 100644
--- a/src/passes/RemoveUnusedBrs.cpp
+++ b/src/passes/RemoveUnusedBrs.cpp
@@ -85,6 +85,9 @@ static bool canTurnIfIntoBrIf(Expression* ifCondition,
 // It can be tuned more later.
 const Index TooCostlyToRunUnconditionally = 9;
 
+static_assert(TooCostlyToRunUnconditionally < CostAnalyzer::Unacceptable,
+              "We never run code unconditionally if it has unacceptable cost");
+
 // Check if it is not worth it to run code unconditionally. This
 // assumes we are trying to run two expressions where previously
 // only one of the two might have executed. We assume here that