WCH has based its RISC-V toolchain on the xPack builds from Liviu Ionescu:

https://github.com/xpack-dev-tools/riscv-none-embed-gcc-xpack/releases/tag/v8.2.0-3.1/

Both output the same version string:

riscv-none-embed-gcc.exe?(xPack?GNU?RISC-V?Embedded?GCC,?32-bit)?8.2.0
Copyright?(C)?2018?Free?Software?Foundation,?Inc.
This?is?free?software;?see?the?source?for?copying?conditions.??There?is?NO
warranty;?not?even?for?MERCHANTABILITY?or?FITNESS?FOR?A?PARTICULAR?PURPOSE.

However, there are some minor differences between the RISC-V toolchain from WCH and the one from xPack. The WCH toolchain supports a few more RISC-V instruction sets, like:

?- rv32ecwx

?- rv32imacxw

?- rv32imafcxw

Question 1:

The 'w' and 'x' letters are non-standard extensions. What do they stand for?

I also notice that the WCH toolchain has the following libraries that don't appear anywhere in the native xPack toolchain:

?- libIQMath_RV32.a

?- libprintf.a

?- libprintfloat.a

Question 2:

What are these non-standard libraries for? I was able to build a sample project with both the WCH toolchain and the native xPack toolchain. In both cases, the printf() function worked just fine, sending characters over the TX line. So I wonder what the libprintf.a library is used for, if the setup works without that library?

Question 3:

Where can I find the source code of the WCH toolchain, and the build instructions?

Thank you very much.