[Optimize Instructions] Fold eqz(eqz(x)) to not-equal of zero (#4855)

eqz(eqz(i32(x)))   ->   i32(x) != 0
eqz(eqz(i64(x)))   ->   i64(x) != 0

Only when shrinkLevel == 0 (prefer speed over binary size).

1 files changed, 17 insertions, 4 deletions

diff --git a/src/passes/OptimizeInstructions.cpp b/src/passes/OptimizeInstructions.cpp
index 828b2fdc9..e3a5774b1 100644
--- a/src/passes/OptimizeInstructions.cpp
+++ b/src/passes/OptimizeInstructions.cpp
@@ -875,11 +875,26 @@ struct OptimizeInstructions
         if (matches(curr, unary(EqZInt32, unary(&inner, WrapInt64, any(&x)))) &&
             Bits::getMaxBits(x, this) <= 32) {
           inner->op = EqZInt64;
-          inner->value = x;
           return replaceCurrent(inner);
         }
       }
       {
+        // i32.eqz(i32.eqz(x))  =>  i32(x) != 0
+        // i32.eqz(i64.eqz(x))  =>  i64(x) != 0
+        //   iff shinkLevel == 0
+        // (1 instruction instead of 2, but 1 more byte)
+        if (getPassRunner()->options.shrinkLevel == 0) {
+          Expression* x;
+          if (matches(curr, unary(EqZInt32, unary(EqZ, any(&x))))) {
+            Builder builder(*getModule());
+            return replaceCurrent(builder.makeBinary(
+              getBinary(x->type, Ne),
+              x,
+              builder.makeConst(Literal::makeZero(x->type))));
+          }
+        }
+      }
+      {
         // i64.extend_i32_s(i32.wrap_i64(x))  =>  x
         //   where maxBits(x) <= 31
         //
@@ -900,12 +915,10 @@ struct OptimizeInstructions
       if (getModule()->features.hasSignExt()) {
         // i64.extend_i32_s(i32.wrap_i64(x))  =>  i64.extend32_s(x)
         Unary* inner;
-        Expression* x;
         if (matches(curr,
-                    unary(ExtendSInt32, unary(&inner, WrapInt64, any(&x))))) {
+                    unary(ExtendSInt32, unary(&inner, WrapInt64, any())))) {
           inner->op = ExtendS32Int64;
           inner->type = Type::i64;
-          inner->value = x;
           return replaceCurrent(inner);
         }
       }