Fix pow2 util and avoid pow2 for left shifting in ZeroRemover (#3293)

Fixes a fuzz bug that was triggered by

#3015 (comment)

but was actually a pre-existing bug in pow2, that that PR just happened
to uncover.

Author: MaxGraey

src/passes/OptimizeInstructions.cpp

@@ -1113,8 +1113,8 @@ struct OptimizeInstructions
 
     struct SeekState {
       Expression* curr;
-      int64_t mul;
-      SeekState(Expression* curr, int64_t mul) : curr(curr), mul(mul) {}
+      uint64_t mul;
+      SeekState(Expression* curr, uint64_t mul) : curr(curr), mul(mul) {}
     };
     std::vector<SeekState> seekStack;
     seekStack.emplace_back(binary, 1);
@@ -1124,8 +1124,8 @@ struct OptimizeInstructions
       auto curr = state.curr;
       auto mul = state.mul;
       if (auto* c = curr->dynCast<Const>()) {
-        int64_t value = c->value.getInteger();
-        if (value != 0LL) {
+        uint64_t value = c->value.getInteger();
+        if (value != 0ULL) {
           constant += value * mul;
           constants.push_back(c);
         }
@@ -1147,17 +1147,19 @@ struct OptimizeInstructions
         } else if (binary->op ==
                    Abstract::getBinary(binary->type, Abstract::Shl)) {
           if (auto* c = binary->right->dynCast<Const>()) {
-            seekStack.emplace_back(
-              binary->left, mul * Bits::pow2(Bits::getEffectiveShifts(c)));
+            seekStack.emplace_back(binary->left,
+                                   mul << Bits::getEffectiveShifts(c));
             continue;
           }
         } else if (binary->op ==
                    Abstract::getBinary(binary->type, Abstract::Mul)) {
           if (auto* c = binary->left->dynCast<Const>()) {
-            seekStack.emplace_back(binary->right, mul * c->value.getInteger());
+            seekStack.emplace_back(binary->right,
+                                   mul * (uint64_t)c->value.getInteger());
             continue;
           } else if (auto* c = binary->right->dynCast<Const>()) {
-            seekStack.emplace_back(binary->left, mul * c->value.getInteger());
+            seekStack.emplace_back(binary->left,
+                                   mul * (uint64_t)c->value.getInteger());
             continue;
           }
         }

src/support/bits.cpp

@@ -196,7 +196,7 @@ uint32_t log2(uint32_t v) {
   return 31 - countLeadingZeroes(v);
 }
 
-uint32_t pow2(uint32_t v) { return 1 << (v & 31); }
+uint32_t pow2(uint32_t v) { return v < 32 ? 1 << v : 0; }
 
 } // namespace Bits
 

test/passes/optimize-instructions_all-features.txt

@@ -1,7 +1,7 @@
 (module
  (type $i32_i32_=>_none (func (param i32 i32)))
- (type $i32_=>_i32 (func (param i32) (result i32)))
  (type $none_=>_i32 (func (result i32)))
+ (type $i32_=>_i32 (func (param i32) (result i32)))
  (type $i32_i64_=>_none (func (param i32 i64)))
  (type $none_=>_none (func))
  (type $i32_i32_=>_i32 (func (param i32 i32) (result i32)))
@@ -2362,6 +2362,15 @@
    )
   )
  )
+ (func $zero-ops-64-special (result i32)
+  (return
+   (i32.wrap_i64
+    (i64.popcnt
+     (i64.const 7377)
+    )
+   )
+  )
+ )
  (func $sign-ext-1-and-ne (result i32)
   (i32.ne
    (i32.and

test/passes/optimize-instructions_all-features.wast

@@ -2683,6 +2683,21 @@
     )
    )
   )
+  (func $zero-ops-64-special (result i32)
+    (return
+      (i32.wrap_i64
+        (i64.popcnt
+          (i64.sub
+            (i64.shl
+              (i64.const 4294783828)
+              (i64.const 17179869183)
+            )
+            (i64.const -7377)
+          )
+        )
+      )
+    )
+  )
   (func $sign-ext-1-and-ne (result i32)
    (select
     (i32.ne