[LLVMdev] Issue with GetElementPtrInst in Instruction Combining pass

[Pankaj Gode]

Yes, it is valid bit code. The command you gave does not give any error to me. 
Actually there is some company specific information and functions in it for the concerned file, so I was not able to share the complete code.
I don't know what I can remove and share so that it is valid and shareable as well :( . 
 
As suggested I have also enabled assertions and debug mode.
 
 
 
Regards,
Pankaj
 
 


________________________________
From: Duncan Sands <baldrick at free.fr>
To: llvmdev at cs.uiuc.edu 
Sent: Thursday, April 19, 2012 6:47 PM
Subject: Re: [LLVMdev] Issue with GetElementPtrInst in Instruction Combining pass

Hi Pankaj, are you testing this on valid bitcode?  The bitcode you sent me did
not pass the verifier, i.e. was not valid.  Optimizers can be expected to do
strange and wrong things if passed invalid bitcode.  That is not a bug in LLVM:
it is user error if a user doesn't use valid bitcode.

Ciao, Duncan.

> I think, finally, I want to conclude on this.
> The problem I see is that if I comment the case for "simplificaiton of bitcast
> to gep of original struct in instruction combining", wherein there is a case for
> if the offset by which GEP moves the pointer is non-zero.
> If I disable this code, then structure elements size, I get is
> --------------------------------------------------------------------------------------------
> Type | struct elements | Size in bytes | Correct size in bytes
> --------------------------------------------------------------------------------------------
> short nScaleFactors *4 2
> *FRAME_INFO frameInfo 36 36
> short domain_vec[MAX_ENVELOPES] 10 10
> short domain_vec_noise[MAX_NOISE_ENVELOPES] 6 4
> INVF_MODE sbr_invf_mode[MAX_INVF_BANDS] 20 20
> COUPLING_MODE coupling 4 4
> short ampResolutionCurrentFrame 2 2
> Flag addHarmonics[MAX_FREQ_COEFFS] 192 192
> short maxQmfSubbandAac 2 2
> short iEnvelope[MAX_NUM_ENVELOPE_VALUES] 480 480
> short sbrNoiseFloorLevel[MAX_NUM_NOISE_VALUES] 20 20
> --------------------------------------------------------------------------------------------
> Though the size i get is wrong, but still my application passes. I don't have
> any reason for that though.
> But, if I enable *this* code, then the structure elements size, I get is:
> --------------------------------------------------------------------------------------------
> Type | struct elements | Size in bytes | Correct size in bytes
> --------------------------------------------------------------------------------------------
> short nScaleFactors 2 2
> FRAME_INFO frameInfo 36 36
> short domain_vec[MAX_ENVELOPES] 10 10
> short domain_vec_noise[MAX_NOISE_ENVELOPES] 4 4
> INVF_MODE sbr_invf_mode[MAX_INVF_BANDS] 20 20
> COUPLING_MODE coupling 4 4
> short ampResolutionCurrentFrame 2 2
> Flag addHarmonics[MAX_FREQ_COEFFS] 192 192
> short maxQmfSubbandAac 2 2
> short iEnvelope[MAX_NUM_ENVELOPE_VALUES] 480 480
> short sbrNoiseFloorLevel[MAX_NUM_NOISE_VALUES] 20 20
> --------------------------------------------------------------------------------------------
> These sizes are the same as I get with llvm2.9 and which matches with
> expected/correct as well. For llvm2.9, my test passes as well with these sizes.
> So I wanted to know, if there is a major change in llvm infrastructure required
> to calculate this offset/size for each structure element or something related to
> this?
> If nothing is changed related to this, i will simply comment out this code, as
> after commenting, it works for me and forget the problem.
> Regards,
> Pankaj
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