[llvm-commits] [llvm-gcc-4.2] r74575 - /llvm-gcc-4.2/trunk/gcc/llvm-convert.cpp

[Dale Johannesen]

On Jun 30, 2009, at 5:45 PMPDT, Chris Lattner wrote:

>
> On Jun 30, 2009, at 4:53 PM, Dale Johannesen wrote:
>
>> Author: johannes
>> Date: Tue Jun 30 18:53:04 2009
>> New Revision: 74575
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=74575&view=rev
>> Log:
>> Fix buildbreaking nonstandardism.  (And I thought I'd
>> never complain C++ doesn't have enough features...)
>
> Hi Dale,
>
> It's not that big of a deal, but please use SmallVector<int, 4> or
> something instead of alloca.  SmallVector works when "N" is more than
> 4 by going to the heap so you won't run out of stack space for large
> N, and is more portable.

I am not a big lover of alloca, but it was used several places in this  
code before I started working on it so I don't think portability can  
be a problem, and the numbers involved cannot be big enough to run out  
of stack space.

> -Chris
>
>>
>>
>> Modified:
>>   llvm-gcc-4.2/trunk/gcc/llvm-convert.cpp
>>
>> Modified: llvm-gcc-4.2/trunk/gcc/llvm-convert.cpp
>> URL: http://llvm.org/viewvc/llvm-project/llvm-gcc-4.2/trunk/gcc/llvm-convert.cpp?rev=74575&r1=74574&r2=74575&view=diff
>>
>> =
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>> =====================================================================
>> --- llvm-gcc-4.2/trunk/gcc/llvm-convert.cpp (original)
>> +++ llvm-gcc-4.2/trunk/gcc/llvm-convert.cpp Tue Jun 30 18:53:04 2009
>> @@ -4010,11 +4010,12 @@
>> {
>>  int MaxWeight = 0;
>>  unsigned int CommasToSkip = 0;
>> -  int Weights[NumChoices];
>> +  int *Weights = (int *)alloca(NumChoices * sizeof(int));
>>  // RunningConstraints is pointers into the Constraints strings which
>>  // are incremented as we go to point to the beginning of each
>>  // comma-separated alternative.
>> -  const char* RunningConstraints[NumInputs+NumOutputs];
>> +  const char** RunningConstraints =
>> +    (const char**)alloca((NumInputs+NumOutputs)*sizeof(const  
>> char*));
>>  memcpy(RunningConstraints, Constraints,
>>         (NumInputs+NumOutputs) * sizeof(const char*));
>>  // The entire point of this loop is to compute CommasToSkip.
>>
>>
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