[crankshaft] Range analysis should not rely on overflowed ranges.

src/crankshaft/hydrogen-instructions.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/crankshaft/hydrogen-instructions.h"
 
 #include "src/base/bits.h"
 #include "src/base/ieee754.h"
 #include "src/base/safe_math.h"
 #include "src/crankshaft/hydrogen-infer-representation.h"
@@ skipping 241 matching lines @@
     lower_ = kMinInt;
   }
   set_can_be_minus_zero(false);
 }
 
 
 bool Range::AddAndCheckOverflow(const Representation& r, Range* other) {
   bool may_overflow = false;
   lower_ = AddWithoutOverflow(r, lower_, other->lower(), &may_overflow);
   upper_ = AddWithoutOverflow(r, upper_, other->upper(), &may_overflow);
-  KeepOrder();
+  if (may_overflow) {
+    Clear();
+  } else {
+    KeepOrder();
+  }
 #ifdef DEBUG
   Verify();
 #endif
   return may_overflow;
 }
 
 
 bool Range::SubAndCheckOverflow(const Representation& r, Range* other) {
   bool may_overflow = false;
   lower_ = SubWithoutOverflow(r, lower_, other->upper(), &may_overflow);
   upper_ = SubWithoutOverflow(r, upper_, other->lower(), &may_overflow);
-  KeepOrder();
+  if (may_overflow) {
+    Clear();
+  } else {
+    KeepOrder();
+  }
 #ifdef DEBUG
   Verify();
 #endif
   return may_overflow;
 }
 
+void Range::Clear() {
+  lower_ = kMinInt;
+  upper_ = kMaxInt;
+}
 
 void Range::KeepOrder() {
   if (lower_ > upper_) {
     int32_t tmp = lower_;
     lower_ = upper_;
     upper_ = tmp;
   }
 }
 
 
 #ifdef DEBUG
 void Range::Verify() const {
   DCHECK(lower_ <= upper_);
 }
 #endif
 
 
 bool Range::MulAndCheckOverflow(const Representation& r, Range* other) {
   bool may_overflow = false;
   int v1 = MulWithoutOverflow(r, lower_, other->lower(), &may_overflow);
   int v2 = MulWithoutOverflow(r, lower_, other->upper(), &may_overflow);
   int v3 = MulWithoutOverflow(r, upper_, other->lower(), &may_overflow);
   int v4 = MulWithoutOverflow(r, upper_, other->upper(), &may_overflow);
-  lower_ = Min(Min(v1, v2), Min(v3, v4));
-  upper_ = Max(Max(v1, v2), Max(v3, v4));
+  if (may_overflow) {
+    Clear();
+  } else {
+    lower_ = Min(Min(v1, v2), Min(v3, v4));
+    upper_ = Max(Max(v1, v2), Max(v3, v4));
+  }
 #ifdef DEBUG
   Verify();
 #endif
   return may_overflow;
 }
 
 
 bool HValue::IsDefinedAfter(HBasicBlock* other) const {
   return block()->block_id() > other->block_id();
 }
@@ skipping 3707 matching lines @@
     case HObjectAccess::kExternalMemory:
       os << "[external-memory]";
       break;
   }
 
   return os << "@" << access.offset();
 }
 
 }  // namespace internal
 }  // namespace v8