[LLVMdev] A strange testing case of SROA

[Shuxin Yang]

Hi, Pete:

    Thank you for the clarification.  Yes, it will incur bug if idx1 == 
idx2. This opt (try to promote
vector-element-insertion/extraction) also incur miscompilation in other 
applications. I have to
disable this optimization, at least, for the time being.

Thanks
Shuxin

On 4/5/13 4:10 PM, Pete Cooper wrote:
> Hi Shuxin
>
> I think i might have written that test.  And yeah, no matter what 
> values you get you’ll get a 0.0.  Its probably a bad test case, but i 
> can’t remember if it exposed a bug in this form or not.  Since writing 
> it Chandler rewrote SROA anyway so the original bug is long gone.
>
> Thanks,
> Pete
> On Apr 5, 2013, at 11:57 AM, Shuxin Yang <shuxin.llvm at gmail.com 
> <mailto:shuxin.llvm at gmail.com>> wrote:
>
>> Hi,
>>
>>   Following is excerpted from dynamic-vector-gep.ll.
>> The resulting "extractelement" seems to always return 0.0f regardless 
>> the value idx1 and idx2 is holding.
>> Am I missing something here or there is something fishy take place?
>>
>> Thanks
>> Shuxin
>>
>>
>> 101 ; CHECK: test6
>> 102 ; CHECK: insertelement <4 x float> zeroinitializer, float 
>> 1.000000e+00, i32 %idx1
>> 103 ; CHECK: extractelement <4 x float> zeroinitializer, i32 %idx2
>> 104
>> 105 %vector.pair = type { %vector.anon, %vector.anon }
>> 106 %vector.anon = type { %vector }
>> 107 %vector = type { <4 x float> }
>> 108
>> 109 ; Dynamic GEPs on vectors were crashing when the vector was 
>> inside a struct
>> 110 ; as the new GEP for the new alloca might not include all the 
>> indices from
>> 111 ; the original GEP, just the indices it needs to get to the 
>> correct offset of
>> 112 ; some type, not necessarily the dynamic vector.
>> 113 ; This test makes sure we don't have this crash.
>> 114 define float @test6(i32 %idx1, i32 %idx2) {
>> 115 entry:
>> 116   %0 = alloca %vector.pair
>> 117   store %vector.pair zeroinitializer, %vector.pair* %0
>> 118   %ptr1 = getelementptr %vector.pair* %0, i32 0, i32 0, i32 0, 
>> i32 0, i32 %idx1
>> 119   store float 1.0, float* %ptr1
>> 120   %ptr2 = getelementptr %vector.pair* %0, i32 0, i32 1, i32 0, 
>> i32 0, i32 %idx2
>> 121   %ret = load float* %ptr2
>> 122   ret float %ret
>> 123 }
>>
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