[PATCH] D129727: [ARM64EC 11/?] Add support for lowering variadic indirect calls.

Mon Sep 26 19:19:47 PDT 2022

bcl5980 added inline comments.

================
Comment at: llvm/lib/Target/AArch64/AArch64ISelLowering.cpp:1467
+    setLibcallName(RTLIB::MEMSET, "#memset");
+    setLibcallName(RTLIB::MEMMOVE, "#memmove");
+  }
----------------
efriedma wrote:
> bcl5980 wrote:
> > efriedma wrote:
> > > Is this actually necessary?  The linker should resolve plain "memcpy" to something reasonable, I think.
> > Based on my local test, if I don't add `#` the memcpy will be link into x86 version memcpy and crash at runtime.
> Does the linking process for arm64ec actually guarantee that we have an arm64ec msvcrt that includes "#memcpy" etc.?  Even if it does, I don't think we can make the same assumption for all the other functions SelectionDAG needs to call.
> 
> Given that, we're going to need some mechanism to allow calls generated by SelectionDAG to participate in thunking.
> 
> In any case, if this change unblocks testing for you, we can leave it in with a FIXME to address the above.
I try to use dumpbin to dump the symbols for vcruntime.lib. And I find those symbols may related:

```
       40 #memchr
       41 #memcmp
       42 #memcpy
       43 #memmove
       44 #memset
```
I think we only need to consider the memory intrinsic functions that MSVC also can export.
We can also add these intrinsic's exit thunk in AArch64TargetLowering::LowerCall.

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D129727/new/

https://reviews.llvm.org/D129727