commit a3db7ac3457f887631d1e8f4d244cdd20d93cbe1
author Dylan McKay <me@dylanmckay.io> Fri Jan 18 06:10:41 2019 +0000
committer Dylan McKay <me@dylanmckay.io> Fri Jan 18 06:10:41 2019 +0000
tree f79ab6e607ae1a29f5d8028dae57d8ebc91aa53e
parent abe6bc1296a96938e277aa2f8ac99f9685a3d79e

[AVR] Expand 8/16-bit multiplication to libcalls on MCUs that don't have hardware MUL

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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@351523 91177308-0d34-0410-b5e6-96231b3b80d8