[llvm-commits] [llvm] r111230 - /llvm/trunk/include/llvm/MC/MCObjectWriter.h

[Daniel Dunbar]

Hi Benjamin,

On Tue, Aug 17, 2010 at 6:55 AM, Benjamin Kramer
<benny.kra at googlemail.com> wrote:
> Author: d0k
> Date: Tue Aug 17 08:55:45 2010
> New Revision: 111230
>
> URL: http://llvm.org/viewvc/llvm-project?rev=111230&view=rev
> Log:
> Micro-optimize MCObjectWriter to do a byteswap if necessary and then write the
> whole integer to the stream instead of doing byte-sized writes.

Gross, IMHO. Adding Host dependencies to portable code, which isn't
performance sensitive, seems like a bad trade to me.

 - Daniel

> Modified:
>    llvm/trunk/include/llvm/MC/MCObjectWriter.h
>
> Modified: llvm/trunk/include/llvm/MC/MCObjectWriter.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/MC/MCObjectWriter.h?rev=111230&r1=111229&r2=111230&view=diff
> ==============================================================================
> --- llvm/trunk/include/llvm/MC/MCObjectWriter.h (original)
> +++ llvm/trunk/include/llvm/MC/MCObjectWriter.h Tue Aug 17 08:55:45 2010
> @@ -10,8 +10,10 @@
>  #ifndef LLVM_MC_MCOBJECTWRITER_H
>  #define LLVM_MC_MCOBJECTWRITER_H
>
> +#include "llvm/Support/MathExtras.h"
>  #include "llvm/Support/raw_ostream.h"
>  #include "llvm/System/DataTypes.h"
> +#include "llvm/System/Host.h"
>  #include <cassert>
>
>  namespace llvm {
> @@ -92,54 +94,57 @@
>   }
>
>   void WriteLE16(uint16_t Value) {
> -    Write8(uint8_t(Value >> 0));
> -    Write8(uint8_t(Value >> 8));
> +    if (sys::isBigEndianHost())
> +      Value = ByteSwap_16(Value);
> +    OS << StringRef((const char*)&Value, sizeof(Value));
>   }
>
>   void WriteLE32(uint32_t Value) {
> -    WriteLE16(uint16_t(Value >> 0));
> -    WriteLE16(uint16_t(Value >> 16));
> +    if (sys::isBigEndianHost())
> +      Value = ByteSwap_32(Value);
> +    OS << StringRef((const char*)&Value, sizeof(Value));
>   }
>
>   void WriteLE64(uint64_t Value) {
> -    WriteLE32(uint32_t(Value >> 0));
> -    WriteLE32(uint32_t(Value >> 32));
> +    if (sys::isBigEndianHost())
> +      Value = ByteSwap_64(Value);
> +    OS << StringRef((const char*)&Value, sizeof(Value));
>   }
>
>   void WriteBE16(uint16_t Value) {
> -    Write8(uint8_t(Value >> 8));
> -    Write8(uint8_t(Value >> 0));
> +    if (sys::isLittleEndianHost())
> +      Value = ByteSwap_16(Value);
> +    OS << StringRef((const char*)&Value, sizeof(Value));
>   }
>
>   void WriteBE32(uint32_t Value) {
> -    WriteBE16(uint16_t(Value >> 16));
> -    WriteBE16(uint16_t(Value >> 0));
> +    if (sys::isLittleEndianHost())
> +      Value = ByteSwap_32(Value);
> +    OS << StringRef((const char*)&Value, sizeof(Value));
>   }
>
>   void WriteBE64(uint64_t Value) {
> -    WriteBE32(uint32_t(Value >> 32));
> -    WriteBE32(uint32_t(Value >> 0));
> +    if (sys::isLittleEndianHost())
> +      Value = ByteSwap_64(Value);
> +    OS << StringRef((const char*)&Value, sizeof(Value));
>   }
>
>   void Write16(uint16_t Value) {
> -    if (IsLittleEndian)
> -      WriteLE16(Value);
> -    else
> -      WriteBE16(Value);
> +    if (IsLittleEndian != sys::isLittleEndianHost())
> +      Value = ByteSwap_16(Value);
> +    OS << StringRef((const char*)&Value, sizeof(Value));
>   }
>
>   void Write32(uint32_t Value) {
> -    if (IsLittleEndian)
> -      WriteLE32(Value);
> -    else
> -      WriteBE32(Value);
> +    if (IsLittleEndian != sys::isLittleEndianHost())
> +      Value = ByteSwap_32(Value);
> +    OS << StringRef((const char*)&Value, sizeof(Value));
>   }
>
>   void Write64(uint64_t Value) {
> -    if (IsLittleEndian)
> -      WriteLE64(Value);
> -    else
> -      WriteBE64(Value);
> +    if (IsLittleEndian != sys::isLittleEndianHost())
> +      Value = ByteSwap_64(Value);
> +    OS << StringRef((const char*)&Value, sizeof(Value));
>   }
>
>   void WriteZeros(unsigned N) {
>
>
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