Ported ia32 optimization of revision 3487 to x64.

src/x64/disasm-x64.cc

Index: src/x64/disasm-x64.cc
diff --git a/src/x64/disasm-x64.cc b/src/x64/disasm-x64.cc
index ce3aae8a2c69a888072801f3e890217fd7be9f71..547daeeb177c18a5179a18b0911a522b1371a9fc 100644
--- a/src/x64/disasm-x64.cc
+++ b/src/x64/disasm-x64.cc
@@ -993,7 +993,60 @@ int DisassemblerX64::TwoByteOpcodeInstruction(byte* data) {
   byte* current = data + 2;
   // At return, "current" points to the start of the next instruction.
   const char* mnemonic = TwoByteMnemonic(opcode);
-  if (opcode == 0x1F) {
+  if (operand_size_ == 0x66) {
+    // 0x66 0x0F prefix.
+    int mod, regop, rm;
+    get_modrm(*current, &mod, &regop, &rm);
+    const char* mnemonic = "?";
+    if (opcode == 0x57) {
+      mnemonic = "xorpd";
+    } else if (opcode == 0x2E) {
+      mnemonic = "comisd";
+    } else if (opcode == 0x2F) {
+      mnemonic = "ucomisd";
+    } else {
+      UnimplementedInstruction();
+    }
+    AppendToBuffer("%s %s,", mnemonic, NameOfXMMRegister(regop));
+    current += PrintRightXMMOperand(current);
+  } else if (group_1_prefix_ == 0xF2) {
+    // Beginning of instructions with prefix 0xF2.
+
+    if (opcode == 0x11 || opcode == 0x10) {
+      // MOVSD: Move scalar double-precision fp to/from/between XMM registers.
+      AppendToBuffer("movsd ");
+      int mod, regop, rm;
+      get_modrm(*current, &mod, &regop, &rm);
+      if (opcode == 0x11) {
+        current += PrintRightOperand(current);
+        AppendToBuffer(",%s", NameOfXMMRegister(regop));
+      } else {
+        AppendToBuffer("%s,", NameOfXMMRegister(regop));
+        current += PrintRightOperand(current);
+      }
+    } else if (opcode == 0x2A) {
+      // CVTSI2SD: integer to XMM double conversion.
+      int mod, regop, rm;
+      get_modrm(*current, &mod, &regop, &rm);
+      AppendToBuffer("%s %s,", mnemonic, NameOfXMMRegister(regop));
+      current += PrintRightOperand(current);
+    } else if ((opcode & 0xF8) == 0x58) {
+      // XMM arithmetic. Mnemonic was retrieved at the start of this function.
+      int mod, regop, rm;
+      get_modrm(*current, &mod, &regop, &rm);
+      AppendToBuffer("%s %s,", mnemonic, NameOfXMMRegister(regop));
+      current += PrintRightXMMOperand(current);
+    } else {
+      UnimplementedInstruction();
+    }
+  } else if (opcode == 0x2C && group_1_prefix_ == 0xF3) {
+    // Instruction with prefix 0xF3.
+
+    // CVTTSS2SI: Convert scalar single-precision FP to dword integer.
+    // Assert that mod is not 3, so source is memory, not an XMM register.
+    ASSERT_NE(0xC0, *current & 0xC0);
+    current += PrintOperands("cvttss2si", REG_OPER_OP_ORDER, current);
+  } else if (opcode == 0x1F) {
     // NOP
     int mod, regop, rm;
     get_modrm(*current, &mod, &regop, &rm);
@@ -1007,8 +1060,7 @@ int DisassemblerX64::TwoByteOpcodeInstruction(byte* data) {
       current += 4;
     }  // else no immediate displacement.
     AppendToBuffer("nop");
-
-  } else  if (opcode == 0xA2 || opcode == 0x31) {
+  } else if (opcode == 0xA2 || opcode == 0x31) {
     // RDTSC or CPUID
     AppendToBuffer("%s", mnemonic);
 
@@ -1043,43 +1095,6 @@ int DisassemblerX64::TwoByteOpcodeInstruction(byte* data) {
     } else {
       AppendToBuffer(",%s,cl", NameOfCPURegister(regop));
     }
-  } else if (group_1_prefix_ == 0xF2) {
-    // Beginning of instructions with prefix 0xF2.
-
-    if (opcode == 0x11 || opcode == 0x10) {
-      // MOVSD: Move scalar double-precision fp to/from/between XMM registers.
-      AppendToBuffer("movsd ");
-      int mod, regop, rm;
-      get_modrm(*current, &mod, &regop, &rm);
-      if (opcode == 0x11) {
-        current += PrintRightOperand(current);
-        AppendToBuffer(",%s", NameOfXMMRegister(regop));
-      } else {
-        AppendToBuffer("%s,", NameOfXMMRegister(regop));
-        current += PrintRightOperand(current);
-      }
-    } else if (opcode == 0x2A) {
-      // CVTSI2SD: integer to XMM double conversion.
-      int mod, regop, rm;
-      get_modrm(*current, &mod, &regop, &rm);
-      AppendToBuffer("%s %s,", mnemonic, NameOfXMMRegister(regop));
-      current += PrintRightOperand(current);
-    } else if ((opcode & 0xF8) == 0x58) {
-      // XMM arithmetic. Mnemonic was retrieved at the start of this function.
-      int mod, regop, rm;
-      get_modrm(*current, &mod, &regop, &rm);
-      AppendToBuffer("%s %s,", mnemonic, NameOfXMMRegister(regop));
-      current += PrintRightXMMOperand(current);
-    } else {
-      UnimplementedInstruction();
-    }
-  } else if (opcode == 0x2C && group_1_prefix_ == 0xF3) {
-    // Instruction with prefix 0xF3.
-
-    // CVTTSS2SI: Convert scalar single-precision FP to dword integer.
-    // Assert that mod is not 3, so source is memory, not an XMM register.
-    ASSERT_NE(0xC0, *current & 0xC0);
-    current += PrintOperands("cvttss2si", REG_OPER_OP_ORDER, current);
   } else {
     UnimplementedInstruction();
   }