[llvm-commits] [llvm] r169157 - /llvm/trunk/lib/Bitcode/Writer/BitcodeWriter.cpp

[Michael Ilseman]

On Dec 3, 2012, at 1:33 PM, Bill Wendling <wendling at apple.com> wrote:

> On Dec 3, 2012, at 1:29 PM, Michael Ilseman <milseman at apple.com> wrote:
> 
>> Author: milseman
>> Date: Mon Dec  3 15:29:36 2012
>> New Revision: 169157
>> 
>> URL: http://llvm.org/viewvc/llvm-project?rev=169157&view=rev
>> Log:
>> Since this SmallVector immediately grows on the next line, don't waste stack space. SmallVector is still needed due to existing APIs growing their arguments
>> 
> Why not make the size 256*1024 instead of 0?
> 

That is an alternate possibility, though that number seems awfully big. What are the general guidelines for trade-offs like these?

> -bw
> 
>> Modified:
>>   llvm/trunk/lib/Bitcode/Writer/BitcodeWriter.cpp
>> 
>> Modified: llvm/trunk/lib/Bitcode/Writer/BitcodeWriter.cpp
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Bitcode/Writer/BitcodeWriter.cpp?rev=169157&r1=169156&r2=169157&view=diff
>> ==============================================================================
>> --- llvm/trunk/lib/Bitcode/Writer/BitcodeWriter.cpp (original)
>> +++ llvm/trunk/lib/Bitcode/Writer/BitcodeWriter.cpp Mon Dec  3 15:29:36 2012
>> @@ -1939,7 +1939,7 @@
>> /// WriteBitcodeToFile - Write the specified module to the specified output
>> /// stream.
>> void llvm::WriteBitcodeToFile(const Module *M, raw_ostream &Out) {
>> -  SmallVector<char, 1024> Buffer;
>> +  SmallVector<char, 0> Buffer;
>>  Buffer.reserve(256*1024);
>> 
>>  // If this is darwin or another generic macho target, reserve space for the
>> 
>> 
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>