[interpreter] Fix and test for printing of bytecodes.

test/unittests/interpreter/bytecodes-unittest.cc

 // Copyright 2015 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 <vector>
 
 #include "src/v8.h"
 
 #include "src/interpreter/bytecodes.h"
 #include "test/unittests/test-utils.h"
@@ skipping 159 matching lines @@
   if (!Bytecodes::IsDebugBreak(Bytecode::k##Name) &&                       \
       !Bytecodes::IsPrefixScalingBytecode(Bytecode::k##Name)) {            \
     Bytecode debug_bytecode = Bytecodes::GetDebugBreak(Bytecode::k##Name); \
     CHECK_EQ(Bytecodes::Size(Bytecode::k##Name, kOperandScale),            \
              Bytecodes::Size(debug_bytecode, kOperandScale));              \
   }
   BYTECODE_LIST(CHECK_DEBUG_BREAK_SIZE)
 #undef CHECK_DEBUG_BREAK_SIZE
 }
 
+TEST(Bytecodes, DecodeBytecodeAndOperands) {
+  struct BytecodesAndResult {
+    const uint8_t bytecode[32];
+    const size_t length;
+    int parameter_count;
+    const char* output;
+  };
+
+#define B(Name) static_cast<uint8_t>(Bytecode::k##Name)
+  const BytecodesAndResult cases[] = {
+      {{B(LdaSmi), 0x01}, 2, 0, "            LdaSmi [1]"},
+      {{B(Wide), B(LdaSmi), 0xe8, 0x03}, 4, 0, "      LdaSmi.Wide [1000]"},
+      {{B(ExtraWide), B(LdaSmi), 0xa0, 0x86, 0x01, 0x00},
+       6,
+       0,
+       "LdaSmi.ExtraWide [100000]"},
+      {{B(LdaSmi), 0xff}, 2, 0, "            LdaSmi [-1]"},
+      {{B(Wide), B(LdaSmi), 0x18, 0xfc}, 4, 0, "      LdaSmi.Wide [-1000]"},
+      {{B(ExtraWide), B(LdaSmi), 0x60, 0x79, 0xfe, 0xff},
+       6,
+       0,
+       "LdaSmi.ExtraWide [-100000]"},
+      {{B(Star), 0xfb}, 2, 0, "            Star r5"},
+      {{B(Wide), B(Star), 0x78, 0xff}, 4, 0, "      Star.Wide r136"},
+      {{B(Wide), B(Call), 0x7a, 0xff, 0x79, 0xff, 0x02, 0x00, 0xb1, 0x00},
+       10,
+       0,
+       "Call.Wide r134, r135, #2, [177]"},
+      {{B(Ldar),
+        static_cast<uint8_t>(Register::FromParameterIndex(2, 3).ToOperand())},
+       2,
+       3,
+       "            Ldar a1"},
+  };
+#undef B
+
+  for (size_t i = 0; i < arraysize(cases); ++i) {
+    // Generate reference string by prepending formatted bytes.
+    std::stringstream expected_ss;
+    std::ios ios_fmt(nullptr);

[rmcilroy, 2016/03/22 17:15:37]

nit - default_format  ?

[oth, 2016/03/23 10:10:06]

Done.

+    ios_fmt.copyfmt(expected_ss);
+    expected_ss.fill('0');

[rmcilroy, 2016/03/22 17:15:37]

nit - newline, and a comment to explain what this is doing (setting formatting
used to write out the prepending raw bytes of the bytecode).

+    expected_ss.flags(std::ios::right | std::ios::hex);
+    for (size_t b = 0; b < cases[i].length; b++) {
+      expected_ss << std::setw(2) << static_cast<uint32_t>(cases[i].bytecode[b])
+                << ' ';
+    }
+    expected_ss.copyfmt(ios_fmt);
+    expected_ss << cases[i].output;
+
+    // Generate decoded byte output.
+    std::stringstream actual_ss;
+    Bytecodes::Decode(actual_ss, cases[i].bytecode, cases[i].parameter_count);
+
+    // Compare.
+    CHECK_EQ(actual_ss.str(), expected_ss.str());
+  }
+}
+
 TEST(Bytecodes, DebugBreakForPrefixBytecodes) {
   CHECK_EQ(Bytecode::kDebugBreakWide,
            Bytecodes::GetDebugBreak(Bytecode::kWide));
   CHECK_EQ(Bytecode::kDebugBreakExtraWide,
            Bytecodes::GetDebugBreak(Bytecode::kExtraWide));
 }
 
 TEST(Bytecodes, PrefixMappings) {
   Bytecode prefixes[] = {Bytecode::kWide, Bytecode::kExtraWide};
   TRACED_FOREACH(Bytecode, prefix, prefixes) {
@@ skipping 18 matching lines @@
       Bytecodes::OperandScaleRequiresPrefixBytecode(OperandScale::kQuadruple));
   CHECK(Bytecodes::OperandScaleToPrefixBytecode(OperandScale::kDouble) ==
         Bytecode::kWide);
   CHECK(Bytecodes::OperandScaleToPrefixBytecode(OperandScale::kQuadruple) ==
         Bytecode::kExtraWide);
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8