GlobalStructInference: Run the safe parts in open world (#8020)

We cannot infer a struct is only created in a global, but we can see
global.gets and optimize them, at least, in a non-type-based way,
even in open world.

Fixes #8016

Author: kripken

scripts/fuzz_opt.py

@@ -2484,7 +2484,6 @@ def write_commands(commands, filename):
                          ("--abstract-type-refining",),
                          ("--cfp",),
                          ("--cfp-reftest",),
-                         ("--gsi",),
                          ("--type-ssa",),
                          ("--type-merging",),
                          ("--unsubtyping",)}

src/passes/GlobalStructInference.cpp

@@ -14,6 +14,9 @@
  * limitations under the License.
  */
 
+//
+// GlobalStructInference: Analyze struct usage globally, in particular, structs
+// created (perhaps only) in globals.
 //
 // Finds types which are only created in assignments to immutable globals. For
 // such types we can replace a struct.get with a global.get when there is a
@@ -47,7 +50,7 @@
 //
 // This also optimizes some related things - reads from structs created in
 // globals - that benefit from the infrastructure here (see unnesting, below),
-// even without this type-based approach.
+// even without this type-based approach, and even in open world.
 //
 // TODO: Only do the case with a select when shrinkLevel == 0?
 //
@@ -81,17 +84,24 @@ struct GlobalStructInference : public Pass {
   //
   // We will remove unoptimizable types from here, so in practice, if a type is
   // optimizable it will have an entry here, and not if not.
+  //
+  // This is filled in when in closed world. In open world, we cannot do such
+  // type-based inference, and this remains empty.
   std::unordered_map<HeapType, std::vector<Name>> typeGlobals;
 
   void run(Module* module) override {
     if (!module->features.hasGC()) {
       return;
     }
 
-    if (!getPassOptions().closedWorld) {
-      Fatal() << "GSI requires --closed-world";
+    if (getPassOptions().closedWorld) {
+      analyzeClosedWorld(module);
     }
 
+    optimize(module);
+  }
+
+  void analyzeClosedWorld(Module* module) {
     // First, find all the information we need. We need to know which struct
     // types are created in functions, because we will not be able to optimize
     // those.
@@ -213,7 +223,9 @@ struct GlobalStructInference : public Pass {
     for (auto& [type, globals] : typeGlobals) {
       std::sort(globals.begin(), globals.end());
     }
+  }
 
+  void optimize(Module* module) {
     // We are looking for the case where we can pick between two values using a
     // single comparison. More than two values, or more than a single
     // comparison, lead to tradeoffs that may not be worth it.

src/passes/pass.cpp

@@ -769,7 +769,9 @@ void PassRunner::addDefaultGlobalOptimizationPrePasses() {
       } else {
         addIfNoDWARFIssues("cfp");
       }
-      addIfNoDWARFIssues("gsi");
+    }
+    addIfNoDWARFIssues("gsi");
+    if (options.closedWorld) {
       addIfNoDWARFIssues("abstract-type-refining");
       addIfNoDWARFIssues("unsubtyping");
     }

test/lit/passes/gsi-nontype.wast

@@ -1,14 +1,17 @@
 ;; NOTE: Assertions have been generated by update_lit_checks.py --all-items and should not be edited.
-;; RUN: foreach %s %t wasm-opt --gsi -all --closed-world -S -o - | filecheck %s
 
-;; Non-type-based optimizations in --gsi
+;; RUN: foreach %s %t wasm-opt --gsi                -all -S -o - | filecheck %s
+;; RUN: foreach %s %t wasm-opt --gsi --closed-world -all -S -o - | filecheck %s
+
+;; Non-type-based optimizations in --gsi, which work in open world too.
 
 ;; Create an immutable vtable in an immutable global, which we can optimize
 ;; with.
 (module
   ;; CHECK:      (type $vtable (struct (field funcref)))
   (type $vtable (struct funcref))
 
+
   ;; CHECK:      (type $1 (func))
 
   ;; CHECK:      (import "a" "b" (global $imported funcref))
@@ -43,6 +46,7 @@
   ;; CHECK:      (type $vtable (struct (field funcref)))
   (type $vtable (struct funcref))
 
+
   ;; CHECK:      (type $1 (func))
 
   ;; CHECK:      (import "a" "b" (global $imported funcref))
@@ -79,6 +83,7 @@
   ;; CHECK:      (type $vtable (struct (field funcref)))
   (type $vtable (struct funcref))
 
+
   ;; CHECK:      (type $1 (func))
 
   ;; CHECK:      (import "a" "b" (global $imported funcref))
@@ -109,11 +114,13 @@
   ;; CHECK:      (type $table (struct (field anyref)))
   (type $table (struct anyref))
 
+
   ;; CHECK:      (type $1 (func))
 
   ;; CHECK:      (import "a" "b" (global $imported funcref))
   (import "a" "b" (global $imported funcref))
 
+
   ;; CHECK:      (global $table.unnested.0 (ref (exact $table)) (struct.new_default $table))
 
   ;; CHECK:      (global $table (ref $table) (struct.new $table
@@ -149,6 +156,7 @@
     (type $desc (sub (describes $struct (struct))))
   )
 
+
   ;; CHECK:      (type $2 (func))
 
   ;; CHECK:      (import "a" "b" (global $imported (ref (exact $desc))))
@@ -183,6 +191,7 @@
   ;; CHECK:      (type $vtable (struct (field funcref)))
   (type $vtable (struct funcref))
 
+
   ;; CHECK:      (type $1 (func))
 
   ;; CHECK:      (import "a" "b" (global $imported (ref $vtable)))
@@ -209,6 +218,7 @@
   ;; CHECK:      (type $A (struct (field i8)))
   (type $A (struct (field i8)))
 
+
   ;; CHECK:      (type $1 (func))
 
   ;; CHECK:      (global $global (ref $A) (struct.new $A
@@ -246,6 +256,7 @@
     (type $A.desc (sub (describes $A (struct))))
   )
 
+
   ;; CHECK:      (type $2 (func (result (ref $A.desc))))
 
   ;; CHECK:      (global $global (ref $A) (struct.new_default $A
@@ -279,6 +290,8 @@
     (type $inner (sub (struct (field (ref $func)))))
   )
 
+
+
   ;; CHECK:      (type $3 (func (result anyref)))
 
   ;; CHECK:      (global $global.unnested.0 (ref (exact $inner)) (struct.new $inner

test/unit/test_passes.py

@@ -36,14 +36,20 @@ def test_O2(self):
                 'signature-refining',
                 'gto',
                 'cfp',
-                'gsi',
             ]
             for pass_ in CLOSED_WORLD_PASSES:
                 if closed_world:
                     self.assertIn(pass_, passes)
                 else:
                     self.assertNotIn(pass_, passes)
 
+            # some passes run in open world too
+            OPEN_WORLD_PASSES = [
+                'gsi',
+            ]
+            for pass_ in OPEN_WORLD_PASSES:
+                self.assertIn(pass_, passes)
+
     def test_O3_O1(self):
         # When we run something like -O3 -O1 we should run -O3 followed by -O1
         # (and not -O1 -O1, which would be the case if the last commandline