[Openmp-commits] [PATCH] D138704: RFC: [openmp] Provide an assembly implementation of __kmp_invoke_microtask on ARM

[David Spickett via Phabricator via Openmp-commits]

DavidSpickett added a comment.

Assembly looks good to me.

Now we need some way to tell if earlier Arm needs to be supported. Is there other existing Arm assembly for OpenMP? That would give a clue, might have to go to the git blame to find the intent when it was first added. I'm no expert but I can help check it for things that look "new" or "old" (for lack of better words).



================
Comment at: openmp/runtime/src/z_Linux_asm.S:1447
+	// We strictly need 4*(argc-2) bytes, but allocate 4*argc for
+	// simplicity (to avoid needing to handle the argc<2 cases).
+	// We align the number of bytes allocated to 8 bytes, to keep the
----------------
mstorsjo wrote:
> DavidSpickett wrote:
> > What is the `-2` in `argc-2`? (or rather what would it be)
> We pass 2 arguments out of `argc` in registers (while the other 2 register parameters are taken by `tid` and `gtid`). In the case of aarch64 with 8 register parameters, they'd need space for `argc-6` arguments on the stack.
How about:
```
// We strictly need 4*(argc-2) bytes (2 arguments are passed in registers)
// but allocate 4*argc for....
```


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https://reviews.llvm.org/D138704