[llvm-dev] Convert Function Pointer Call to Function Call at the IR Level

[Ahmad Nouralizadeh Khorrami via llvm-dev]

Thanks.

On 18 August 2018 at 11:56, mayuyu.io <admin at mayuyu.io> wrote:

> Yep. We encountered similar issue a while ago due to IR linking. A
> bitcasted function argument would do
>
> Zhang
>
> 在 2018年8月17日，19:30，Ahmad Nouralizadeh Khorrami via llvm-dev <
> llvm-dev at lists.llvm.org> 写道：
>
> Hi.
> It seems that `struct.demuxer.2657*` is different from `struct.demuxer*`.
> Should I add something like a `bitcast` before the call?
> Thanks!
>
> On 16 August 2018 at 15:45, Ahmad Nouralizadeh Khorrami <
> ahmad.llvm at gmail.com> wrote:
>
>> Hi,
>> I want to convert a function pointer call in the IR of MPlayer to a
>> function call. For example, I have the following line:
>> ...
>> %10 = tail call i32 %7(%struct.demuxer* nonnull %0, i32 %1, i8* %2) #7,
>> !dbg !863222
>> ...
>> I want to set the target which is stored in %7 to a real function called
>> "demux_lavf_control()" with the following definition:
>> ...
>> define internal i32 @demux_lavf_control(%struct.demuxer.2657* nocapture
>> readonly, i32, i8* nocapture) #0 !dbg !963916 {
>> ...
>> I wrote a function pass and found the mentioned function pointer call
>> (here, stored in "CallInstr") and set the call target as follows:
>> ...
>> Module *theModule = F.getParent();
>> Function *targetFunc = theModule->getFunction("demux_lavf_control");
>> CalIInstr->setCalledFunction(targetFunc);
>> ...
>> "F" is the function containing the call. But it leads to the following
>> error:
>> ...
>> Call parameter type does not match function signature!
>> %struct.demuxer* %0
>>  %struct.demuxer.2657*  %10 = tail call i32 @demux_lavf_control(%
>> struct.demuxer* nonnull %0, i32 %1, i8* %2) #7, !dbg !863222
>> LLVM ERROR: Broken function found, compilation aborted!
>> ...
>> The [names:types] of call operands before the change is:
>> ...
>> [:%struct.demuxer*]
>> [:i32]
>> [:i8*]
>> [:i32 (%struct.demuxer*, i32, i8*)*]
>> ...
>> And after the change is:
>> ...
>> [:%struct.demuxer*]
>> [:i32]
>> [:i8*]
>> [demux_lavf_control:i32 (%struct.demuxer.2657*, i32, i8*)*]
>> ...
>> How can I solve the problem?
>> Thanks in advance!
>>
>
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