[LLVMdev] Auto-vectorization in GCC 4.0

[Vikram Adve]

Does llvmgcc4 convert the high-level AST to LLVM (like llvmgcc3x) or  
does it go from GIMPL to LLVM?  If the latter, would it be possible  
to allow some TreeSSA optimizations before emitting LLVM?

--Vikram
http://www.cs.uiuc.edu/~vadve
http://llvm.cs.uiuc.edu/


On Jul 31, 2006, at 1:10 PM, Devang Patel wrote:

> llvmgcc4 emits LLVM byte code before executing GCC optimizations,  
> so one can say that llvmgcc4 disables all GCC optimizations.
>
> On Jul 31, 2006, at 11:01 AM, Zhiru Zhang wrote:
>
>> Hi,
>> I am trying to turn on the new GCC auto-vectorization feature  
>> within llvmgcc4. Below is the command I used, but nothing was  
>> vectorized. Does it mean that llvmgcc4 has disabled this  
>> optimization and all I can do is to embed SSE intrinsics in the  
>> source code by hand?
>>
>> Thanks!
>>
>> ./llvm-gcc4-x86/bin/llvm-gcc -c -O2 -ftree-vectorize -msse -ftree- 
>> vectorizer-verbose=5 -emit-llvm vec.c -o vec.bc
>>
>> ////////////////////vec.c/////////////////////////
>> int a[256], b[256], c[256];
>> foo () {
>>   int i;
>>   for (i=0; i<256; i++){
>>     a[i] = b[i] + c[i];
>>   }
>> }
>>
>>
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>
> -
> Devang
>
>
>
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