[Wasm GC] Global Refining pass (#4344)

Fairly simple, this uses the existing infrastructure to find opportunities
to refine the type of a global variable. This a common pattern in j2wasm
for example, where a global begins as a null of $java.lang.Object (the
least specific type) but it is in practice always assigned an object of
some specific type.

1 files changed, 3 insertions, 0 deletions

diff --git a/src/passes/pass.cpp b/src/passes/pass.cpp
index 49615d81b..d20a5edcd 100644
--- a/src/passes/pass.cpp
+++ b/src/passes/pass.cpp
@@ -155,6 +155,8 @@ void PassRegistry::registerPasses() {
   registerPass(
     "generate-stack-ir", "generate Stack IR", createGenerateStackIRPass);
   registerPass(
+    "global-refining", "refine the types of globals", createGlobalRefiningPass);
+  registerPass(
     "gto", "globally optimize GC types", createGlobalTypeOptimizationPass);
   registerPass("type-refining",
                "apply more specific subtypes to type fields where possible",
@@ -528,6 +530,7 @@ void PassRunner::addDefaultGlobalOptimizationPrePasses() {
   if (wasm->features.hasGC() && getTypeSystem() == TypeSystem::Nominal &&
       options.optimizeLevel >= 2) {
     addIfNoDWARFIssues("type-refining");
+    addIfNoDWARFIssues("global-refining");
     // Global type optimization can remove fields that are not needed, which can
     // remove ref.funcs that were once assigned to vtables but are no longer
     // needed, which can allow more code to be removed globally. After those,