Revert "Bit width analysis for avoiding conversion of bitops to unsigned."

pkg/compiler/lib/src/ssa/codegen.dart

Index: pkg/compiler/lib/src/ssa/codegen.dart
diff --git a/pkg/compiler/lib/src/ssa/codegen.dart b/pkg/compiler/lib/src/ssa/codegen.dart
index 08a66d49666e439c37057b86b0ee2187e8fbf524..c882259fbdd51f9eb75271f782de0f219773e067 100644
--- a/pkg/compiler/lib/src/ssa/codegen.dart
+++ b/pkg/compiler/lib/src/ssa/codegen.dart
@@ -2,7 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'dart:math' as math;
 import '../common.dart';
 import '../common/codegen.dart' show CodegenRegistry, CodegenWorkItem;
 import '../common/tasks.dart' show CompilerTask;
@@ -211,58 +210,8 @@ class SsaCodeGenerator implements HVisitor, HBlockInformationVisitor {
     return false;
   }
 
-  // Returns the number of bits occupied by the value computed by [instruction].
-  // Returns `32` if the value is negative or does not fit in a smaller number
-  // of bits.
-  int bitWidth(HInstruction instruction) {
-    const int MAX = 32;
-    int constant(HInstruction insn) {
-      if (insn.isConstantInteger()) {
-        IntConstantValue constant = insn.constant;
-        return constant.primitiveValue;
-      }
-      return null;
-    }
-
-    if (instruction.isConstantInteger()) {
-      int value = constant(instruction);
-      if (value < 0) return MAX;
-      if (value > ((1 << 31) - 1)) return MAX;
-      return value.bitLength;
-    }
-    if (instruction is HBitAnd) {
-      return math.min(bitWidth(instruction.left), bitWidth(instruction.right));
-    }
-    if (instruction is HBitOr || instruction is HBitXor) {
-      int leftWidth = bitWidth(instruction.left);
-      if (leftWidth == MAX) return MAX;
-      return math.max(leftWidth, bitWidth(instruction.right));
-    }
-    if (instruction is HShiftLeft) {
-      int shiftCount = constant(instruction.right);
-      if (shiftCount == null || shiftCount < 0 || shiftCount > 31) return MAX;
-      int leftWidth = bitWidth(instruction.left);
-      int width = leftWidth + shiftCount;
-      return math.min(width, MAX);
-    }
-    if (instruction is HShiftRight) {
-      int shiftCount = constant(instruction.right);
-      if (shiftCount == null || shiftCount < 0 || shiftCount > 31) return MAX;
-      int leftWidth = bitWidth(instruction.left);
-      if (leftWidth >= MAX) return MAX;
-      return math.max(leftWidth - shiftCount, 0);
-    }
-    if (instruction is HAdd) {
-      return math.min(
-          1 + math.max(bitWidth(instruction.left), bitWidth(instruction.right)),
-          MAX);
-    }
-    return MAX;
-  }
-
   bool requiresUintConversion(instruction) {
     if (instruction.isUInt31(compiler)) return false;
-    if (bitWidth(instruction) <= 31) return false;
     // If the result of a bit-operation is only used by other bit
     // operations, we do not have to convert to an unsigned integer.
     return hasNonBitOpUser(instruction, new Set<HPhi>());