Add infrastructure to query LLVM backend for specific assembly mnemonics
and use it in compiletest to conditionally run tests based on instruction
availability.
This fixes test failures with naked-dead-code-elimination which requires
the `RET` mnemonic.
Co-authored-by: Folkert de Vries <flokkievids@gmail.com>
Tests for `-Zdebuginfo-compression=zstd` need to be skipped if LLVM was built
without support for zstd compression.
Currently, compiletest relies on messy and fragile heuristics to detect whether
the compiler's LLVM was built with zstd support. But the compiler itself
already knows whether LLVM has zstd or not, so it's easier for compiletest to
just ask the compiler.
This schema is helpful for people writing custom target spec JSON. It
can provide autocomplete in the editor, and also serves as documentation
when there are documentation comments on the structs, as `schemars` will
put them in the schema.
Eddy (Eduard) Stefes