[clang] [clang] Enable --print-supported-extensions for all targets (PR #66586)

[Balint Cristian via cfe-commits]

cbalint13 wrote:


@DavidSpickett 

Hi David, 

> Thankyou for looking into this, if it can work it's much cleaner than an ever expanding if.
> 
> I think that `getAllProcessorFeatures` may include things that are rejected by `-march`. I will check that for Arm and AArch64. Since the list of features in the target parser may be different than the backend (it's not good but it is what it is).


* I see the important point of ```-march```. 

   To be accurate , we can filter/validate through llvm ```MCInfo->checkFeatures()``` with respect to the -mcpu (if user provides it, otherwise return a full list just like now).

   Something like:
   ```
   $ zcat sample-outputs.log.gz | grep print
   $ ./bin/clang --target=riscv64-unknown-linux-gnu  --print-supported-extensions
   $ ./bin/clang --target=riscv64-unknown-linux-gnu -mcpu=sifive-x280 --print-supported-extensions
   $ ./bin/clang --target=x86_64-unknown-linux-gnu --print-supported-extensions
   $ ./bin/clang --target=x86_64-unknown-linux-gnu -mcpu=sandybridge --print-supported-extensions
   $ ./bin/clang --target=x86_64-unknown-linux-gnu -mcpu=cascadelake --print-supported-extensions
   $ ./bin/clang --target=aarch64-unknown-linux-gnu --print-supported-extensions
   $ ./bin/clang --target=aarch64-unknown-linux-gnu  -mcpu=cortex-a55 --print-supported-extensions
   ```
   The file with the full log outputs is here: [sample-outputs.log.gz](https://github.com/llvm/llvm-project/files/12646975/sample-outputs.log.gz)



> Does this change RISC-V's output? They are (I assume) unique in printing version numbers and ratification status, etc. Assuming it doesn't (which it probably does), it would likely make a few methods in RSIC-V ABI info unused, but deal with that later if so.

* If user provides ```-mcpu``` we can narrow the flags the only to validated ones for that target+mcpu, see:

```
$ ./bin/clang --target=riscv64-unknown-linux-gnu -mcpu=sifive-x280 --print-supported-extensions
All available -march extensions for riscv64 and -mcpu sifive-x280

  64bit                                    Implements RV64
  a                                        'A' (Atomic Instructions)
  c                                        'C' (Compressed Instructions)
  d                                        'D' (Double-Precision Floating-Point)
  dlen-factor-2                            Vector unit DLEN(data path width) is half of VLEN
  f                                        'F' (Single-Precision Floating-Point)
  m                                        'M' (Integer Multiplication and Division)
  no-default-unroll                        Disable default unroll preference.
  short-forward-branch-opt                 Enable short forward branch optimization
  sifive7                                  SiFive 7-Series processors
  v                                        'V' (Vector Extension for Application Processors)
  zba                                      'Zba' (Address Generation Instructions)
  zbb                                      'Zbb' (Basic Bit-Manipulation)
  zfh                                      'Zfh' (Half-Precision Floating-Point)
  zfhmin                                   'Zfhmin' (Half-Precision Floating-Point Minimal)
  zicsr                                    'zicsr' (CSRs)
  zifencei                                 'Zifencei' (fence.i)
  zve32f                                   'Zve32f' (Vector Extensions for Embedded Processors with maximal 32 EEW and F extension)
  zve32x                                   'Zve32x' (Vector Extensions for Embedded Processors with maximal 32 EEW)
  zve64d                                   'Zve64d' (Vector Extensions for Embedded Processors with maximal 64 EEW, F and D extension)
  zve64f                                   'Zve64f' (Vector Extensions for Embedded Processors with maximal 64 EEW and F extension)
  zve64x                                   'Zve64x' (Vector Extensions for Embedded Processors with maximal 64 EEW)
  zvfh                                     'Zvfh' (Vector Half-Precision Floating-Point)
  zvl128b                                  'Zvl' (Minimum Vector Length) 128
  zvl256b                                  'Zvl' (Minimum Vector Length) 256
  zvl32b                                   'Zvl' (Minimum Vector Length) 32
  zvl512b                                  'Zvl' (Minimum Vector Length) 512
  zvl64b                                   'Zvl' (Minimum Vector Length) 64

```



----

In current state this PR prints _all_ flags of target, it is not mcpu aware.
I don't know how to drag into [cc1_main()](https://github.com/llvm/llvm-project/blob/08d2ea372ff63156939a439dfb30766d83686764/clang/tools/driver/cc1_main.cpp#L218) the user's -mcpu flag from clang's main().

An attempt to do it is here, but propagading down the ```-mcpu``` fails many unittests: [clang-print-mcpu-aware.patch.gz](https://github.com/llvm/llvm-project/files/12646535/clang-print-mcpu-aware.patch.gz)







https://github.com/llvm/llvm-project/pull/66586