[ros-dev] [hbelusca] 64773: [FAST486]: Do not call RtlCopyMemory for copying few bytes (2 and 4).

[Love Nystrom]

@Hermes, @Alex,

May I suggest using my LITERAL macro for that sort of thing..?
The explicit leftcast blurb is not exactly best for readability,
and a call overhead for such a puny transfer is bad performance.

#define LITERAL( type,var )  (*(type*)&var)  // Omnipotent cast

Then
     *((PUSHORT)&TableReg) = State->Idtr.Size;
     *((PULONG)&TableReg[sizeof(USHORT)]) = State->Idtr.Address;

Becomes
     LITERAL( USHORT, TableReg ) = State->Idtr.Size;
     LITERAL( ULONG, TableReg[2] ) = State->Idtr.Address;

Which is far easier to read, ergo less prone to mistakes,
and does not incur a call overhead.

Best Regards
// Love

On 2014-10-21 01.50, Alex Ionescu wrote:
> memcpy already has logic to handle, 1, 2, 4, 8, etc.. sizes.
>
> Best regards,
> Alex Ionescu
>
> On Thu, Oct 16, 2014 at 2:48 PM, <hbelusca at svn.reactos.org 
> <mailto:hbelusca at svn.reactos.org>> wrote:
>
>     Author: hbelusca
>     Date: Thu Oct 16 21:48:18 2014
>     New Revision: 64773
>
>     URL: http://svn.reactos.org/svn/reactos?rev=64773&view=rev
>     Log:
>     [FAST486]: Do not call RtlCopyMemory for copying few bytes (2 and 4).
>
>     Modified:
>         trunk/reactos/lib/fast486/fast486.c
>         trunk/reactos/lib/fast486/opgroups.c
>
>     Modified: trunk/reactos/lib/fast486/fast486.c
>     URL:
>     http://svn.reactos.org/svn/reactos/trunk/reactos/lib/fast486/fast486.c?rev=64773&r1=64772&r2=64773&view=diff
>     ==============================================================================
>     --- trunk/reactos/lib/fast486/fast486.c [iso-8859-1] (original)
>     +++ trunk/reactos/lib/fast486/fast486.c [iso-8859-1] Thu Oct 16
>     21:48:18 2014
>     @@ -117,7 +117,6 @@
>      Fast486MemReadCallback(PFAST486_STATE State, ULONG Address, PVOID
>     Buffer, ULONG Size)
>      {
>          UNREFERENCED_PARAMETER(State);
>     -
>          RtlMoveMemory(Buffer, (PVOID)Address, Size);
>      }
>
>     @@ -126,7 +125,6 @@
>      Fast486MemWriteCallback(PFAST486_STATE State, ULONG Address,
>     PVOID Buffer, ULONG Size)
>      {
>          UNREFERENCED_PARAMETER(State);
>     -
>          RtlMoveMemory((PVOID)Address, Buffer, Size);
>      }
>
>
>     Modified: trunk/reactos/lib/fast486/opgroups.c
>     URL:
>     http://svn.reactos.org/svn/reactos/trunk/reactos/lib/fast486/opgroups.c?rev=64773&r1=64772&r2=64773&view=diff
>     ==============================================================================
>     --- trunk/reactos/lib/fast486/opgroups.c        [iso-8859-1]
>     (original)
>     +++ trunk/reactos/lib/fast486/opgroups.c        [iso-8859-1] Thu
>     Oct 16 21:48:18 2014
>     @@ -2016,6 +2016,7 @@
>
>      FAST486_OPCODE_HANDLER(Fast486OpcodeGroup0F01)
>      {
>     +    // FAST486_TABLE_REG TableReg;
>          UCHAR TableReg[6];
>          FAST486_MOD_REG_RM ModRegRm;
>          BOOLEAN OperandSize, AddressSize;
>     @@ -2054,8 +2055,9 @@
>                  }
>
>                  /* Fill the 6-byte table register */
>     -            RtlCopyMemory(TableReg, &State->Gdtr.Size,
>     sizeof(USHORT));
>     -            RtlCopyMemory(&TableReg[sizeof(USHORT)],
>     &State->Gdtr.Address, sizeof(ULONG));
>     +            // TableReg = State->Gdtr;
>     +            *((PUSHORT)&TableReg) = State->Gdtr.Size;
>     +            *((PULONG)&TableReg[sizeof(USHORT)]) =
>     State->Gdtr.Address;
>
>                  /* Store the GDTR */
>                  return Fast486WriteMemory(State,
>     @@ -2076,8 +2078,9 @@
>                  }
>
>                  /* Fill the 6-byte table register */
>     -            RtlCopyMemory(TableReg, &State->Idtr.Size,
>     sizeof(USHORT));
>     -            RtlCopyMemory(&TableReg[sizeof(USHORT)],
>     &State->Idtr.Address, sizeof(ULONG));
>     +            // TableReg = State->Idtr;
>     +            *((PUSHORT)&TableReg) = State->Idtr.Size;
>     +            *((PULONG)&TableReg[sizeof(USHORT)]) =
>     State->Idtr.Address;
>
>                  /* Store the IDTR */
>                  return Fast486WriteMemory(State,
>     @@ -2117,7 +2120,8 @@
>                  }
>
>                  /* Load the new GDT */
>     -            State->Gdtr.Size = *((PUSHORT)TableReg);
>     +            // State->Gdtr = TableReg;
>     +            State->Gdtr.Size = *((PUSHORT)&TableReg);
>                  State->Gdtr.Address =
>     *((PULONG)&TableReg[sizeof(USHORT)]);
>
>                  /* In 16-bit mode the highest byte is masked out */
>     @@ -2156,7 +2160,8 @@
>                  }
>
>                  /* Load the new IDT */
>     -            State->Idtr.Size = *((PUSHORT)TableReg);
>     +            // State->Idtr = TableReg;
>     +            State->Idtr.Size = *((PUSHORT)&TableReg);
>                  State->Idtr.Address =
>     *((PULONG)&TableReg[sizeof(USHORT)]);
>
>                  /* In 16-bit mode the highest byte is masked out */
>
>
>

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