Improved range analysis for bitwise operations.

src/hydrogen-instructions.cc

Index: src/hydrogen-instructions.cc
===================================================================
--- src/hydrogen-instructions.cc	(revision 15052)
+++ src/hydrogen-instructions.cc	(working copy)
@@ -285,16 +285,8 @@
 }
 
 
-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;
+void Range::ToBitRange(BitRange* bits) const {
+  BitRange::SetFromRange(bits, lower_, upper_);
 }
 
 
@@ -2347,6 +2339,7 @@
 
 
 Range* HBitwise::InferRange(Zone* zone) {
+  /*
   if (op() == Token::BIT_XOR) {
     if (left()->HasRange() && right()->HasRange()) {
       // The maximum value has the high bit, and all bits below, set:
@@ -2391,6 +2384,37 @@
   return (result_mask >= 0)
       ? new(zone) Range(0, result_mask)
       : HValue::InferRange(zone);
+  */

[fschneider, 2013/06/11 10:22:37]

Remove commented code.

[sra1, 2013/06/12 00:12:24]

Done.

+  if (representation().IsInteger32()) {
+    BitRange left_bits, right_bits;
+
+    if (left()->range() != NULL)

[Toon Verwaest, 2013/06/11 12:47:46]

if (left()->HasRange()) {
...
}

[sra1, 2013/06/12 00:12:24]

Done.

+      left()->range()->ToBitRange(&left_bits);
+
+    if (right()->range() != NULL)
+      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);
+  }
 }