Fix binary writing of local name indexes (#3649)

When writing a binary, we take the local indexes in the IR and turn
them into the format in the binary, which clumps them by type. When
writing the names section we should be aware of that ordering, but
we never were, as noticed in #3499

This fixes that by saving the mapping of locals when we are emitting
the name section, then using it when emitting the local names.

This also fixes the order of the types themselves as part of the
refactoring. We used to depend on the ordering of types to decide
which to emit first, but that isn't good for at least two reasons. First,
it hits #3648 - that order is not fully
defined for recursive types. Also, it's not good for code size - we've
ordered the locals in a way we think is best already (ReorderLocals pass).
This PR makes us pick an order of types based on that, as much as
possible, that is, when we see a type for the first time we append it to
a list whose order we use.

Test changes: Some are just because we use a different order than
before, as in atomics64. But some are actual fixes, e.g. in heap-types
where we now have (local $tv (ref null $vector)) which is indeed
right - v there is for vector, and likewise m for matrix etc. - we
just had wrong names before. Another example, we now have
(local $local_externref externref) whereas before the name was
funcref, and which was wrong... seems like the incorrectness was
more common on reference types and GC types, which is why this was
not noticed before.

Fixes #3499

Makes part of #3648 moot.

1 files changed, 19 insertions, 0 deletions

diff --git a/test/passes/reorder-locals_print_roundtrip.wast b/test/passes/reorder-locals_print_roundtrip.wast
new file mode 100644
index 000000000..764c16470
--- /dev/null
+++ b/test/passes/reorder-locals_print_roundtrip.wast
@@ -0,0 +1,19 @@
+(module
+  (func $a
+    (local $x i32)
+    (local $y f64)
+    ;; x appears twice
+    (drop (local.get $x))
+    (drop (local.get $x))
+    (drop (local.get $y))
+  )
+  (func $b
+    (local $x i32)
+    (local $y f64)
+    ;; y appears twice, so it will be reordered to be first, and that should be
+    ;; preserved in the binary format
+    (drop (local.get $x))
+    (drop (local.get $y))
+    (drop (local.get $y))
+  )
+)