[llvm-commits] [llvm] r162873 - in /llvm/trunk: include/llvm/Support/Compiler.h lib/Support/raw_ostream.cpp

[Benjamin Kramer]

On 30.08.2012, at 01:18, Chandler Carruth <chandlerc at google.com> wrote:

> On Wed, Aug 29, 2012 at 3:57 PM, Benjamin Kramer <benny.kra at googlemail.com> wrote:
> Author: d0k
> Date: Wed Aug 29 17:57:00 2012
> New Revision: 162873
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=162873&view=rev
> Log:
> Replace the BUILTIN_EXPECT macro with a less horrible LLVM_LIKELY/LLVM_UNLIKELY interface.
> 
> Modified:
>     llvm/trunk/include/llvm/Support/Compiler.h
>     llvm/trunk/lib/Support/raw_ostream.cpp
> 
> Modified: llvm/trunk/include/llvm/Support/Compiler.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/Compiler.h?rev=162873&r1=162872&r2=162873&view=diff
> ==============================================================================
> --- llvm/trunk/include/llvm/Support/Compiler.h (original)
> +++ llvm/trunk/include/llvm/Support/Compiler.h Wed Aug 29 17:57:00 2012
> @@ -106,9 +106,11 @@
>  #endif
> 
>  #if (__GNUC__ >= 4)
> -#define BUILTIN_EXPECT(EXPR, VALUE) __builtin_expect((EXPR), (VALUE))
> +#define LLVM_LIKELY(EXPR) __builtin_expect((EXPR), true)
> +#define LLVM_UNLIKELY(EXPR) __builtin_expect((EXPR), false)
> 
> Do you want to cast (EXPR) to bool before handing it to __builtin_expect? The true variant will do the wrong thing for integers in some weird cases without that...

Yup, that's safer and better fits the if(LLVM_LIKELY(…)) idiom. Added bool casts in r162877.

- Ben

>  
>  #else
> -#define BUILTIN_EXPECT(EXPR, VALUE) (EXPR)
> +#define LLVM_LIKELY(EXPR) (EXPR)
> +#define LLVM_UNLIKELY(EXPR) (EXPR)
>  #endif
> 
> 
> 
> Modified: llvm/trunk/lib/Support/raw_ostream.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/raw_ostream.cpp?rev=162873&r1=162872&r2=162873&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Support/raw_ostream.cpp (original)
> +++ llvm/trunk/lib/Support/raw_ostream.cpp Wed Aug 29 17:57:00 2012
> @@ -266,8 +266,8 @@
> 
>  raw_ostream &raw_ostream::write(unsigned char C) {
>    // Group exceptional cases into a single branch.
> -  if (BUILTIN_EXPECT(OutBufCur >= OutBufEnd, false)) {
> -    if (BUILTIN_EXPECT(!OutBufStart, false)) {
> +  if (LLVM_UNLIKELY(OutBufCur >= OutBufEnd)) {
> +    if (LLVM_UNLIKELY(!OutBufStart)) {
>        if (BufferMode == Unbuffered) {
>          write_impl(reinterpret_cast<char*>(&C), 1);
>          return *this;
> @@ -286,8 +286,8 @@
> 
>  raw_ostream &raw_ostream::write(const char *Ptr, size_t Size) {
>    // Group exceptional cases into a single branch.
> -  if (BUILTIN_EXPECT(size_t(OutBufEnd - OutBufCur) < Size, false)) {
> -    if (BUILTIN_EXPECT(!OutBufStart, false)) {
> +  if (LLVM_UNLIKELY(size_t(OutBufEnd - OutBufCur) < Size)) {
> +    if (LLVM_UNLIKELY(!OutBufStart)) {
>        if (BufferMode == Unbuffered) {
>          write_impl(Ptr, Size);
>          return *this;
> @@ -302,7 +302,7 @@
>      // If the buffer is empty at this point we have a string that is larger
>      // than the buffer. Directly write the chunk that is a multiple of the
>      // preferred buffer size and put the remainder in the buffer.
> -    if (BUILTIN_EXPECT(OutBufCur == OutBufStart, false)) {
> +    if (LLVM_UNLIKELY(OutBufCur == OutBufStart)) {
>        size_t BytesToWrite = Size - (Size % NumBytes);
>        write_impl(Ptr, BytesToWrite);
>        copy_to_buffer(Ptr + BytesToWrite, Size - BytesToWrite);
> @@ -523,7 +523,7 @@
>      ssize_t ret;
> 
>      // Check whether we should attempt to use atomic writes.
> -    if (BUILTIN_EXPECT(!UseAtomicWrites, true)) {
> +    if (LLVM_LIKELY(!UseAtomicWrites)) {
>        ret = ::write(FD, Ptr, Size);
>      } else {
>        // Use ::writev() where available.
> 
> 
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