[llvm-dev] Help with bitcast instruction

[Alberto Barbaro via llvm-dev]

Hi,
I'm playing with the IR of pngpixel and I encountered this instruction:

call void bitcast (void (%struct.png_struct_def.68*, i8*, i8*
(%struct.png_struct_def.68*, i64)*, void (%struct.png_struct_def.68*,
i8*)*)* @png_set_mem_fn to void (%struct.png_struct_def*, i8*, i8*
(%struct.png_struct_def*, i64)*, void (%struct.png_struct_def*,
i8*)*)*)(%struct.png_struct_def* %create_struct, i8* %mem_ptr, i8*
(%struct.png_struct_def*, i64)* %malloc_fn, void (%struct.png_struct_def*,
i8*)* %free_fn) #15

I would like to understand where bitcast is defined because it is not
defined within libpng. I also noticed that the @ is not present, what does
the missing @ mean? I guess it must be an LLVM function.

The bitcast operation seems to represent the following C code:

if (png_ptr != NULL)
   {
      png_ptr->mem_ptr = mem_ptr;
      png_ptr->malloc_fn = malloc_fn;
      png_ptr->free_fn = free_fn;
   }
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