SimplifyGlobals: Connect adjacent blocks in LinearExecutionWalker (#5865)

Followup to #5860, this does the same for SimplifyGlobals as for SimplifyLocals.

As there, this is valid because it's ok if we branch away. This part of the pass
applies a global value to a global.get based on a dominating global.set, so any
dominance is good enough for us.

2 files changed, 60 insertions, 0 deletions

diff --git a/src/passes/SimplifyGlobals.cpp b/src/passes/SimplifyGlobals.cpp
index 97e91bbab..398a6c3ca 100644
--- a/src/passes/SimplifyGlobals.cpp
+++ b/src/passes/SimplifyGlobals.cpp
@@ -341,6 +341,11 @@ struct ConstantGlobalApplier
     return std::make_unique<ConstantGlobalApplier>(constantGlobals, optimize);
   }
 
+  // It is ok to look at adjacent blocks together, as if a later part of a block
+  // is not reached that is fine - changes we make there would not be reached in
+  // that case.
+  bool connectAdjacentBlocks = true;
+
   bool refinalize = false;
 
   void replaceCurrent(Expression* rep) {
diff --git a/test/lit/passes/simplify-globals-dominance.wast b/test/lit/passes/simplify-globals-dominance.wast
new file mode 100644
index 000000000..948e8c5ec
--- /dev/null
+++ b/test/lit/passes/simplify-globals-dominance.wast
@@ -0,0 +1,55 @@
+;; NOTE: Assertions have been generated by update_lit_checks.py --all-items and should not be edited.
+
+;; RUN: foreach %s %t wasm-opt --simplify-globals -all -S -o - | filecheck %s
+
+(module
+  ;; CHECK:      (type $none_=>_none (func))
+
+  ;; CHECK:      (global $global (mut i32) (i32.const 0))
+  (global $global (mut i32) (i32.const 0))
+
+  ;; CHECK:      (func $test (type $none_=>_none)
+  ;; CHECK-NEXT:  (global.set $global
+  ;; CHECK-NEXT:   (i32.const 10)
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (if
+  ;; CHECK-NEXT:   (i32.const 0)
+  ;; CHECK-NEXT:   (block
+  ;; CHECK-NEXT:    (drop
+  ;; CHECK-NEXT:     (i32.const 10)
+  ;; CHECK-NEXT:    )
+  ;; CHECK-NEXT:    (call $test)
+  ;; CHECK-NEXT:    (drop
+  ;; CHECK-NEXT:     (global.get $global)
+  ;; CHECK-NEXT:    )
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:   (drop
+  ;; CHECK-NEXT:    (global.get $global)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT: )
+  (func $test
+    (global.set $global
+      (i32.const 10)
+    )
+    (if
+      (i32.const 0)
+      (block
+        ;; This is dominated by the set, so we can apply 10 here.
+        (drop
+          (global.get $global)
+        )
+        (call $test)
+        ;; This is after a call, so we do nothing (we are still dominated by the
+        ;; global.set, but the call might set the global to another value).
+        (drop
+          (global.get $global)
+        )
+      )
+      ;; This is dominated by the set, but we do not optimize it yet. TODO
+      (drop
+        (global.get $global)
+      )
+    )
+  )
+)