[PATCH] D145088: [RISCV] Add attribute(riscv_rvv_vector_bits(N)) based on AArch64 arm_sve_vector_bits.

[Craig Topper via Phabricator via cfe-commits]

craig.topper added inline comments.


================
Comment at: clang/test/SemaCXX/attr-riscv-rvv-vector-bits.cpp:12
+
+template<typename T> struct S { T var; };
+
----------------
erichkeane wrote:
> craig.topper wrote:
> > @erichkeane does this cover the dependent case or were you looking for something else?
> > 
> > Here are on the only mentions of template I see in SVE tests that use this attribute.
> > 
> > ```
> > clang/test$ ack template `ack arm_sve_vector -l`
> > CodeGenCXX/aarch64-mangle-sve-fixed-vectors.cpp
> > 37:template <typename T> struct S {};
> > 
> > SemaCXX/attr-arm-sve-vector-bits.cpp
> > 16:template<typename T> struct S { T var; };
> > ```
> > 
> > Here is the result for this patch
> > 
> > ```
> > clang/test$ ack template `ack riscv_rvv_vector -l`
> > CodeGenCXX/riscv-mangle-rvv-fixed-vectors.cpp
> > 48:template <typename T> struct S {};
> > 
> > SemaCXX/attr-riscv-rvv-vector-bits.cpp
> > 12:template<typename T> struct S { T var; };
> > ```
> Thats unfortunate, and I wish I'd thought of it at the time/been more active reviewing the SVE stuff then.  Really what I'm looking for is:
> 
> ```
> template<int N> 
> struct Whatever {
>   using Something = char __attribute((riscv_rvv_vector_bits(N)));
> };
> 
> void Func(Whatever<5>::Something MyVar){}
> 
> ```
That does not appear to work.

```
$ ./bin/clang test.cpp --target=riscv64 -march=rv64gcv -mrvv-vector-bits=zvl
test.cpp:3:41: error: 'riscv_rvv_vector_bits' attribute requires an integer constant
    using Something = char __attribute((riscv_rvv_vector_bits(N)));
```

It's not very useful as a template parameter. There's only one value that works and that's whatever __RISCV_RVV_VLEN_BITS is set to.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D145088/new/

https://reviews.llvm.org/D145088