This commit changes a target triple like "armv6m-none-eabi" to
"armv6m-unknown-unknow-eabi". The reason is that while the former is
correctly parsed in Clang (due to normalization), it wasn't parsed
correctly in LLVM meaning that the environment wasn't set to EABI.
This change normalizes all target triples and uses the EABI environment
(-eabi in the triple) for Cortex-M targets.
This change also drops the `--target=` flag in the target JSON files,
the flag is now added implicitly in `(*compileopts.Config).CFlags()`.
This removes some duplication in target JSON files.
Unfortunately, this change also increases code size for Cortex-M
targets. It looks like LLVM now emits calls like __aeabi_memmove instead
of memmove, which pull in slightly more code (they basically just call
the regular C functions) and the calls themself don't seem to be as
efficient as they could be. Perhaps this is a LLVM bug that will be
fixed in the future, as this is a very common occurrence.
The -Qunused-arguments flag disables the warning where some flags are
not relevant to a compilation. This commonly happens when compiling
assembly files (.s or .S files) because some flags are specific to C and
not relevant to assembly.
Because practically all baremetal targets need some form of assembly,
this flag is added to most CFlags. This creates a lot of noise. And it
is also added for compiling C code where it might hide bugs (by hiding
the fact a flag is actually unused).
This commit adds the flag to all assembly compilations and removes them
from all target JSON files.
Eventually we might want to start using the FPU, but the easy option
right now is to simply disable it everywhere. Previously, it depended on
whether Clang was built as part of TinyGo or it was an external binary.
By setting the floating point mode explicitly, such inconsistencies are
avoided.
This commit creates a new cortex-m4 target which can be the central
place for setting FPU-related settings across all Cortex-M4 chips.
