[interpreter] Fix and test for printing of bytecodes.

BUG=v8:4280,v8:4747
LOG=N

Review URL: https://codereview.chromium.org/1825103002

Cr-Commit-Position: refs/heads/master@{#35024}

src/interpreter/bytecodes.cc

@@ -491,6 +491,7 @@ std::ostream& Bytecodes::Decode(std::ostream& os, const uint8_t* bytecode_start,
   OperandScale operand_scale = OperandScale::kSingle;
   if (IsPrefixScalingBytecode(bytecode)) {
     prefix_offset = 1;
+    operand_scale = Bytecodes::PrefixBytecodeToOperandScale(bytecode);
     bytecode = Bytecodes::FromByte(bytecode_start[1]);
   }
   int bytecode_size = Bytecodes::Size(bytecode, operand_scale);

test/unittests/interpreter/bytecodes-unittest.cc

@@ -177,6 +177,74 @@ TEST(Bytecodes, DebugBreakExistForEachBytecode) {
 #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"},
+      {{B(Wide), B(CreateObjectLiteral), 0x01, 0x02, 0x03, 0x04, 0xa5},
+       7,
+       0,
+       "CreateObjectLiteral.Wide [513], [1027], #165"},
+      {{B(ExtraWide), B(JumpIfNull), 0x15, 0xcd, 0x5b, 0x07},
+       6,
+       0,
+       "JumpIfNull.ExtraWide [123456789]"},
+  };
+#undef B
+
+  for (size_t i = 0; i < arraysize(cases); ++i) {
+    // Generate reference string by prepending formatted bytes.
+    std::stringstream expected_ss;
+    std::ios default_format(nullptr);
+    default_format.copyfmt(expected_ss);
+    // Match format of Bytecodes::Decode() for byte representations.
+    expected_ss.fill('0');
+    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(default_format);
+    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));