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

[Jakub Staszak]

BUILTIN_EXPECT also supported SwitchInst, which is impossible for LLVM_LIKELY. Nobody probably ever used that though. Also, you may want to upgrade docs/BranchWeightMetadata.html.

- Kuba

On Aug 30, 2012, at 1:30 AM, Benjamin Kramer <benny.kra at gmail.com> wrote:

> 
> 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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>> 
> 
> 
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