This change modifies the LLVM ISel lowering settings so that
8-bit/16-bit multiplication is expanded to calls into the compiler
runtime library if the MCU being targeted does not support
multiplication in hardware.
Before this, MUL instructions would be generated on CPUs like the
ATtiny85, triggering a CPU reset due to an illegal instruction at
runtime.
First raised in https://github.com/avr-rust/rust/issues/124.
llvm-svn: 351523
Once MULHS was expanded, this exposed an issue where the condition
register was thought to be 16-bit. This caused an attempt to copy a
16-bit register to an 8-bit register.
Authored by Jake Goulding
llvm-svn: 283634
Dylan McKay