[Multibyte] Fix GUFA on multibyte reads of different types (#8531)

Previously we'd filter i8 data with an i64 read into nothing.

Author: kripken

src/ir/possible-contents.cpp

@@ -2976,6 +2976,17 @@ void Flower::filterExpressionContents(PossibleContents& contents,
   std::cout << "TNHOracle informs us that " << *exprLoc.expr << " contains "
             << maximalContents << "\n";
 #endif
+
+  if (exprLoc.expr->is<ArrayLoad>()) {
+    // ArrayLoad cannot filter, as we can have writes of different sizes than
+    // the type of the location (e.g. write i32, do an i64.load). If there is
+    // any content, just report the maximal content, basically like a Memory.
+    if (!contents.isNone()) {
+      contents = maximalContents;
+    }
+    return;
+  }
+
   contents.intersect(maximalContents);
   if (contents.isNone()) {
     // Nothing was left here at all.

test/lit/passes/gufa-multibyte.wast

@@ -0,0 +1,61 @@
+;; NOTE: Assertions have been generated by update_lit_checks.py --all-items and should not be edited.
+;; RUN: foreach %s %t wasm-opt -all --gufa --closed-world -S -o - | filecheck %s
+
+(module
+ ;; CHECK:      (type $0 (func))
+
+ ;; CHECK:      (type $array (array (mut i8)))
+ (type $array (array (mut i8)))
+
+ ;; CHECK:      (export "test" (func $test))
+
+ ;; CHECK:      (func $test (type $0)
+ ;; CHECK-NEXT:  (drop
+ ;; CHECK-NEXT:   (i64.load32_u (type $array)
+ ;; CHECK-NEXT:    (array.new_default $array
+ ;; CHECK-NEXT:     (i32.const 69)
+ ;; CHECK-NEXT:    )
+ ;; CHECK-NEXT:    (i32.const 0)
+ ;; CHECK-NEXT:   )
+ ;; CHECK-NEXT:  )
+ ;; CHECK-NEXT: )
+ (func $test (export "test")
+  ;; We initialize with i8s, and read an i64. That should not confuse us, and
+  ;; we do not optimize here (though we could, in theory, if we tracked the
+  ;; bytes and saw the i64 must be 0).
+  (drop
+   (i64.load32_u (type $array)
+    (array.new_default $array
+     (i32.const 69)
+    )
+    (i32.const 0)
+   )
+  )
+ )
+)
+
+(module
+ ;; CHECK:      (type $array (array (mut i8)))
+ (type $array (array (mut i8)))
+
+ ;; CHECK:      (type $1 (func (param (ref $array))))
+
+ ;; CHECK:      (export "test" (func $test))
+
+ ;; CHECK:      (func $test (type $1) (param $array (ref $array))
+ ;; CHECK-NEXT:  (drop
+ ;; CHECK-NEXT:   (unreachable)
+ ;; CHECK-NEXT:  )
+ ;; CHECK-NEXT: )
+ (func $test (export "test") (param $array (ref $array))
+  ;; As above, but now no $array is ever created (and we are in closed world).
+  ;; We can optimize this to trap.
+  (drop
+   (i64.load32_u (type $array)
+    (local.get $array)
+    (i32.const 0)
+   )
+  )
+ )
+)
+