make: Add support for specifying a different compiler for assembler

[jnohlgard]

This will allow us to specify a separate compiler for assembly sources which are compiled with GCC (not AS). Clang has a problem with some of the assembly headers in the MIPS port and using GCC for the asm sources instead will allow Clang to build all of the C code. PR on the MIPS part is coming.

[kaspar030]

Couldn't we just use gcc as AS?

[jnohlgard]

I did not try to change any behaviour, just allow us to specify a separate compiler for assembler sources being built with gcc (*.S). There are assembly sources built using as too, these are named *.s, lowercase s.

[jnohlgard]

Ping @kaspar030

[kaspar030]

I did not try to change any behaviour, just allow us to specify a separate compiler for assembler sources being built with gcc (*.S). There are assembly sources built using as too, these are named *.s, lowercase s.

Just so I understand, there are some assembly files in the MIPS code that clang doesn't like, but gcc compiles fine?

Can we get rid of ASSMSRC vs ASMSRC? gcc invokes gnu as, clang invokes the llvm assembler. Both run the preprocessor on *.S, not on *.s.
Maybe we can get away with just one rule for both *.s and *.S, and use "gcc" for gnu, "clang" for llvm, and in the special mips case, use "gcc" even for llvm as selected toolchain.

[jnohlgard]

Just so I understand, there are some assembly files in the MIPS code that clang doesn't like, but gcc compiles fine?

Correct

Can we get rid of ASSMSRC vs ASMSRC? ...

Yes, let's do that.

[jnohlgard]

But could we merge this in the meantime while we work on that change?

[kaspar030]

ACK.