[PATCH] D156136: [BPF] Clean up SelLowering

[Eduard Zingerman via Phabricator via llvm-commits]

eddyz87 added inline comments.


================
Comment at: llvm/lib/Target/BPF/BPFISelLowering.cpp:379
+  if (MF.getFunction().hasStructRetAttr())
+    fail(DL, DAG, "sret functions are not supported");
 
----------------
tamird wrote:
> yonghong-song wrote:
> > User may not understand what 'sret' means without looking at source code.
> > Maybe 'functions with returning struct are not supported'?
> Thanks, I agree this error message is not very clear. I'd like to update it, but I notice that the existing tests do not cover it. Do you know how to write a function that would produce IR with the `sret` attribute?
The following C code sample:

```
struct bar { long a[100]; };
struct bar foo(void) {
  struct bar b;
  return b;
}
```

Produces IR that triggers the error:

```
$ clang -mcpu=v4 -O2 --target=bpf -S test3.c -emit-llvm -o -
...
%struct.bar = type { [100 x i64] }

; Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
define dso_local void @foo(ptr noalias nocapture sret(%struct.bar) align 8 %agg.result) local_unnamed_addr #0 {
entry:
  ret void
}
...
$ clang -mcpu=v4 -O2 --target=bpf -S test3.c -emit-llvm -o - | llc
...
error: <unknown>:0:0: in function foo void (ptr): functions with VarArgs or StructRet are not supported
...
```


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D156136/new/

https://reviews.llvm.org/D156136