[PATCH] D71124: [RISCV] support clang driver to select cpu

[Sam Elliott via Phabricator via llvm-commits]

lenary added a comment.

I've got one major issue (inline below), and I'm confused by some other behaviour:

When I run `clang --target=riscv64 -mcpu=?`, the list includes both `generic-rv32` and `generic-rv64`. It doesn't show only the 64-bit cpus. This is not changed by giving a full triple, or by additionally specifying `-march=rv64gc`. Should it be?

For instance, this output:

  $ clang --target=riscv64-unknown-elf -mcpu=\? -march=rv64gc
  clang version 11.0.0
  Target: riscv64-unknown-unknown-elf
  Thread model: posix
  InstalledDir: /home/selliott/llvm-project/./build/llvm_clang/all/bin
  Available CPUs for this target:
  
  	generic-rv32
  	generic-rv64
  	rocket-rv32
  	rocket-rv64
  	sifive-e31
  	sifive-u54
  
  Use -mcpu or -mtune to specify the target's processor.
  For example, clang --target=aarch64-unknown-linux-gui -mcpu=cortex-a35



================
Comment at: clang/lib/Driver/ToolChains/Arch/RISCV.cpp:599
+      return "lp64";
   }
 }
----------------
I now get a stacktrace here if I call `clang --target=riscv32 -march=unknown foo.c -c`. In clang-10, you get a nice error:
```
clang-10: error: invalid arch name 'wat', string must begin with rv32{i,e,g} or rv64{i,g}
```

The stacktrace is coming from the call to `getRISCVABI` in `findRISCVBareMetalMultilibs` (in `clang/lib/Driver/ToolChains/Gnu.cpp:1608`).




Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D71124/new/

https://reviews.llvm.org/D71124