[Turbofan] Fix instruction selector to handle switch with no case

Instruction selector computes the range of case statement labels
to choose between a table or lookup based switch. We need to special
case this when there are no case statements.

Bug: chromium:794825
Change-Id: I46ef57d17f5e2b99a3570f7f3c4ff06e75d78fab
Reviewed-on: https://chromium-review.googlesource.com/830013Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Mythri Alle <mythria@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50153}

src/compiler/instruction-selector.cc

@@ -1018,11 +1018,15 @@ void InstructionSelector::VisitControl(BasicBlock* block) {
         if (sw.min_value > value) sw.min_value = value;
         if (sw.max_value < value) sw.max_value = value;
       }
+      if (sw.case_count != 0) {
         DCHECK_LE(sw.min_value, sw.max_value);
         // Note that {value_range} can be 0 if {min_value} is -2^31 and
         // {max_value} is 2^31-1, so don't assume that it's non-zero below.
         sw.value_range = 1u + bit_cast<uint32_t>(sw.max_value) -
                          bit_cast<uint32_t>(sw.min_value);
+      } else {
+        sw.value_range = 0;
+      }
       return VisitSwitch(input, sw);
     }
     case BasicBlock::kReturn: {

test/mjsunit/regress/regress-794825.js

+// Copyright 2017 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Flags: --allow-natives-syntax --opt
+
+
+function* opt() {
+  // The for loop to generate a SwitchOnSmiNoFeedback with holes
+  // at the end since yield will be eliminated.
+  for (;;)
+    if (true) {
+    } else {
+      yield;
+    }
+
+  // Another loop to force more holes in the constant pool to
+  // verify if bounds checks works when iterating over the jump
+  // table.
+  for (;;)
+    if (true) {
+    } else {
+      yield;
+    }
+}
+
+opt();
+// Optimize function to trigger the iteration over jump
+// table.
+%OptimizeFunctionOnNextCall(opt);
+opt();
+assertOptimized(opt);