Revert "Improved range analysis for bitwise operations."

src/hydrogen-instructions.cc

Index: src/hydrogen-instructions.cc
diff --git a/src/hydrogen-instructions.cc b/src/hydrogen-instructions.cc
index 8e418e4c76cc1edb6709124657e3d5af4c597927..f69fbc9b938cc5466d859771eb707ee1b1762c54 100644
--- a/src/hydrogen-instructions.cc
+++ b/src/hydrogen-instructions.cc
@@ -289,8 +289,16 @@ static int32_t MulWithoutOverflow(int32_t a, int32_t b, bool* overflow) {
 }
 
 
-void Range::ToBitRange(BitRange* bits) const {
-  BitRange::SetFromRange(bits, lower_, upper_);
+int32_t Range::Mask() const {
+  if (lower_ == upper_) return lower_;
+  if (lower_ >= 0) {
+    int32_t res = 1;
+    while (res < upper_) {
+      res = (res << 1) | 1;
+    }
+    return res;
+  }
+  return 0xffffffff;
 }
 
 
@@ -2374,38 +2382,50 @@ void HMathMinMax::InferRepresentation(HInferRepresentation* h_infer) {
 
 
 Range* HBitwise::InferRange(Zone* zone) {
-  if (representation().IsInteger32()) {
-    BitRange left_bits, right_bits;
-
-    if (left()->HasRange()) {
-      left()->range()->ToBitRange(&left_bits);
+  if (op() == Token::BIT_XOR) {
+    if (left()->HasRange() && right()->HasRange()) {
+      // The maximum value has the high bit, and all bits below, set:
+      // (1 << high) - 1.
+      // If the range can be negative, the minimum int is a negative number with
+      // the high bit, and all bits below, unset:
+      // -(1 << high).
+      // If it cannot be negative, conservatively choose 0 as minimum int.
+      int64_t left_upper = left()->range()->upper();
+      int64_t left_lower = left()->range()->lower();
+      int64_t right_upper = right()->range()->upper();
+      int64_t right_lower = right()->range()->lower();
+
+      if (left_upper < 0) left_upper = ~left_upper;
+      if (left_lower < 0) left_lower = ~left_lower;
+      if (right_upper < 0) right_upper = ~right_upper;
+      if (right_lower < 0) right_lower = ~right_lower;
+
+      int high = MostSignificantBit(
+          static_cast<uint32_t>(
+              left_upper | left_lower | right_upper | right_lower));
+
+      int64_t limit = 1;
+      limit <<= high;
+      int32_t min = (left()->range()->CanBeNegative() ||
+                     right()->range()->CanBeNegative())
+                    ? static_cast<int32_t>(-limit) : 0;
+      return new(zone) Range(min, static_cast<int32_t>(limit - 1));
     }
-
-    if (right()->HasRange()) {
-      right()->range()->ToBitRange(&right_bits);
-    }
-
-    BitRange result;
-    switch (op()) {
-      case Token::BIT_AND:
-        result = BitRange::And(left_bits, right_bits);
-        break;
-      case Token::BIT_OR:
-        result = BitRange::Or(left_bits, right_bits);
-        break;
-      case Token::BIT_XOR:
-        result = BitRange::Xor(left_bits, right_bits);
-        break;
-      default:
-        UNREACHABLE();
-    }
-
-    int32_t lower = kMaxInt, upper = kMinInt;  // 'empty' range.
-    result.ExtendRange(&lower, &upper);
-    return new(zone) Range(lower, upper);
-  } else {
     return HValue::InferRange(zone);
   }
+  const int32_t kDefaultMask = static_cast<int32_t>(0xffffffff);
+  int32_t left_mask = (left()->range() != NULL)
+      ? left()->range()->Mask()
+      : kDefaultMask;
+  int32_t right_mask = (right()->range() != NULL)
+      ? right()->range()->Mask()
+      : kDefaultMask;
+  int32_t result_mask = (op() == Token::BIT_AND)
+      ? left_mask & right_mask
+      : left_mask | right_mask;
+  return (result_mask >= 0)
+      ? new(zone) Range(0, result_mask)
+      : HValue::InferRange(zone);
 }