Vacuum: Ignore effects at the entire function scope when possible (#5053)

Recently we added logic to ignore effects that don't "escape" past the function call.
That is, e.g. local.set only affects the current function scope, and once the call stack
is unwound it no longer matters as an effect. This moves that logic to a shared place,
and uses it in the core Vacuum logic.

The new constructor in EffectAnalyzer receives a function and then scans it as
a whole. This works just like e.g. scanning a Block as a whole (if we see a break in
the block, that has an effect only inside it, and the Block + children doesn't have a
branch effect).

Various tests are updated so they don't optimize away trivially, by adding new
return values for them.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/passes/Vacuum.cpp b/src/passes/Vacuum.cpp
index 208e973da..a29c74a89 100644
--- a/src/passes/Vacuum.cpp
+++ b/src/passes/Vacuum.cpp
@@ -390,7 +390,7 @@ struct Vacuum : public WalkerPass<ExpressionStackWalker<Vacuum>> {
       ExpressionManipulator::nop(curr->body);
     }
     if (curr->getResults() == Type::none &&
-        !EffectAnalyzer(getPassOptions(), *getModule(), curr->body)
+        !EffectAnalyzer(getPassOptions(), *getModule(), curr)
            .hasUnremovableSideEffects()) {
       ExpressionManipulator::nop(curr->body);
     }