OptimizeInstructions: Optimize eqz of fallthrough const (#7558)

Precompute doesn't do math computations like

(i32.eqz
 (local.tee $x
  (i32.const 1)
 )
)

It could emit 0 on the outside, but it would repeat the operation each
time the pass is run, which we don't want

Instead, handle this in OptimizeInstructions.

Fixes: #7492

Author: xuruiyang2002

src/passes/OptimizeInstructions.cpp

@@ -2891,6 +2891,12 @@ struct OptimizeInstructions
             }
           }
         }
+        if (unary->op == EqZInt32 || unary->op == EqZInt64) {
+          if (auto* c = getFallthrough(unary->value)->dynCast<Const>()) {
+            return getDroppedChildrenAndAppend(
+              unary, Literal::makeFromInt32(c->value.isZero(), Type::i32));
+          }
+        }
       }
     } else if (auto* binary = boolean->dynCast<Binary>()) {
       if (binary->op == SubInt32) {

test/lit/passes/optimize-instructions-ignore-traps.wast

@@ -688,6 +688,7 @@
 
  ;; CHECK:      (func $conditionalize-if-type-change (type $3) (result f64)
  ;; CHECK-NEXT:  (local $0 i32)
+ ;; CHECK-NEXT:  (local $1 i64)
  ;; CHECK-NEXT:  (drop
  ;; CHECK-NEXT:   (loop $label$1 (result f32)
  ;; CHECK-NEXT:    (block $label$2 (result f32)
@@ -709,7 +710,7 @@
  ;; CHECK-NEXT:           (i64.const 58)
  ;; CHECK-NEXT:           (i64.const -982757)
  ;; CHECK-NEXT:           (i64.eqz
- ;; CHECK-NEXT:            (i64.const 0)
+ ;; CHECK-NEXT:            (local.get $1)
  ;; CHECK-NEXT:           )
  ;; CHECK-NEXT:          )
  ;; CHECK-NEXT:         )
@@ -725,6 +726,7 @@
  ;; CHECK-NEXT: )
  (func $conditionalize-if-type-change (result f64)
   (local $0 i32)
+  (local $1 i64)
   (drop
    (loop $label$1 (result f32)
     (block $label$2 (result f32)
@@ -746,7 +748,7 @@
            (i64.const 58)
            (i64.const -982757)
            (i64.eqz
-            (i64.const 0)
+            (local.get $1)
            )
           )
          )