[sdiy] Some Audio DSP prototypes

[Eric Brombaugh]

On 4/22/22 01:17, Gordonjcp wrote:
> 
> Out of interest, how hard is it to switch from gcc to LLVM, for fairly standard C code with odd sprinklings of assembler?  How much would I need to change?  If it's something fairly straightforward that a couple of #ifdefs can cope with it'd be nice to give folk the choice.

After all the noise here about Clang/LLVM I've decided to look into 
exactly this. I've been using GCC with a straight-forward Makefile flow, 
so I figured it shouldn't be too difficult. A bit of googling turned up 
this tutorial which is specifically for embedded ARM stuff:

https://interrupt.memfault.com/blog/arm-cortexm-with-llvm-clang

The quick summary is that LLVM can understand a great many of GCC's 
compiler options, and you can use GCC to give you additional details 
that LLVM might need. The linked article has some errors and omissions 
that I had to work around, but after a few hours of banging on it I've 
gotten one of my STMF303 projects to compile without errors.

*However* although the compile appears clean, when I try to load it onto 
the hardware the whole thing grinds to a halt - the linking process 
appears to have failed somewhere and the code isn't being flashed to the 
correct address. Using objcpy results in a binary file that's about 4GB 
in size (the .elf is only 200kB, which is comparable to the .elf I get 
from GCC), so there's clearly more work to do.

I'm hopeful that I can get this going at some point in order to make a 
more informed comparison for myself, but I've set it aside for now. I 
realize that the free version I'm using is apparently not the best, but 
I'm not shelling out kilobucks for a quick spin.

If anyone has suggestions I'd be glad to try them out, and I'll 
certainly post results if/when I get it going.

Eric