[Wasm GC] Optimize array.set stored values (#3690)

Same as we already do for struct.set.

3 files changed, 26 insertions, 1 deletions

diff --git a/src/passes/OptimizeInstructions.cpp b/src/passes/OptimizeInstructions.cpp
index 7f02eb283..7e6b00212 100644
--- a/src/passes/OptimizeInstructions.cpp
+++ b/src/passes/OptimizeInstructions.cpp
@@ -998,6 +998,13 @@ struct OptimizeInstructions
     }
   }
 
+  void visitArraySet(ArraySet* curr) {
+    if (curr->ref->type != Type::unreachable && curr->value->type.isInteger()) {
+      auto element = curr->ref->type.getHeapType().getArray().element;
+      optimizeStoredValue(curr->value, element.getByteSize());
+    }
+  }
+
   Index getMaxBitsForLocal(LocalGet* get) {
     // check what we know about the local
     return localInfo[get->index].maxBits;
diff --git a/test/lit/passes/optimize-instructions-gc.wast b/test/lit/passes/optimize-instructions-gc.wast
index 6a0341856..96cd19583 100644
--- a/test/lit/passes/optimize-instructions-gc.wast
+++ b/test/lit/passes/optimize-instructions-gc.wast
@@ -12,6 +12,8 @@
     (field $i64 (mut i64))
   ))
 
+  (type $array (array (mut i8)))
+
   ;; These functions test if an `if` with subtyped arms is correctly folded
   ;; 1. if its `ifTrue` and `ifFalse` arms are identical (can fold)
   ;; CHECK:      (func $if-arms-subtype-fold (result anyref)
@@ -72,4 +74,20 @@
       )
     )
   )
+
+  ;; Similar, but for arrays.
+  ;; CHECK:      (func $store-trunc2 (param $x (ref null $array))
+  ;; CHECK-NEXT:  (array.set $array
+  ;; CHECK-NEXT:   (local.get $x)
+  ;; CHECK-NEXT:   (i32.const 0)
+  ;; CHECK-NEXT:   (i32.const 35)
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT: )
+  (func $store-trunc2 (param $x (ref null $array))
+    (array.set $array
+      (local.get $x)
+      (i32.const 0)
+      (i32.const 0x123) ;; data over 0xff is unnecessary
+    )
+  )
 )
diff --git a/test/passes/Oz_fuzz-exec_all-features.txt b/test/passes/Oz_fuzz-exec_all-features.txt
index 377d936fd..54b204163 100644
--- a/test/passes/Oz_fuzz-exec_all-features.txt
+++ b/test/passes/Oz_fuzz-exec_all-features.txt
@@ -106,7 +106,7 @@
   (array.set $bytes
    (local.get $0)
    (i32.const 10)
-   (i32.const 65408)
+   (i32.const 128)
   )
   (call $log
    (array.get_u $bytes