[LLVMdev] remove redundant load by GVN() does not work

[Xiangyang Guo]

Thanks, Daniel. basicaa works.

Regards

Xiangyang

On Sun, Apr 19, 2015 at 1:56 AM, Daniel Berlin <dberlin at dberlin.org> wrote:

> Add basicaa.  Without aa, it won't touch these
>
> On Sat, Apr 18, 2015, 8:33 PM Xiangyang Guo <xguo6 at ncsu.edu> wrote:
>
>> Hi,
>>
>> Assume I have the following code. The first four instructions in each BB
>> does the same thing. So I think GVN() can remove the redundant code.
>> However, after I apply GVN to my module by "Passes.add(createGVNPass())"
>> and  "Passes.run(*myModule)". It seems GVN does not remove the redundant
>> instructions. Can anyone give me a hint what's going on here? Any hint is
>> appreciable.
>>
>> *********************************************************************
>> cond_3:                                           ; preds = %cond_1_else
>>   %a1 = load i32** @a
>>   %v41 = load i32* %v4
>>   %6 = getelementptr i32* %a1, i32 %v41
>>   %7 = load i32* %6
>>   %8 = icmp slt i32 %7, 1
>>   br i1 %8, label %cond_4, label %cond_4_else
>>
>> cond_4_else:                                      ; preds = %cond_3
>>   %a2 = load i32** @a
>>   %v42 = load i32* %v4
>>   %9 = getelementptr i32* %a2, i32 %v42
>>   %10 = load i32* %9
>>   %11 = icmp sgt i32 %10, %v6_int_34
>>   br i1 %11, label %cond_4, label %cond_4_else1
>>
>> cond_4_else1:                                     ; preds = %cond_4_else
>>   %a3 = load i32** @a
>>   %v43 = load i32* %v4
>>   %12 = getelementptr i32* %a3, i32 %v43
>>   %13 = load i32* %12
>>   %v5_int_42 = srem i32 %v2_int_.0, %13
>>   %14 = icmp eq i32 %v5_int_42, 0
>>   br i1 %14, label %cond_4_else2, label %cond_4
>>
>> ************************************************************************
>> (I change the variable's name a little bit for the first four
>> instructions in each BB because the name of variables in my original IR has
>> a long.)
>>
>> Regards
>>
>> Xiangyang
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>>
>
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