On -ftrapv vs. libcalls...

[Joern Rennecke]

> there.  Or else the REG_EQUAL note should be changed to be accurate, but 
> that would probably require creating a new RTL operator, e.g. multv.

No, that wouldn't work, because REG_EQUAL describes a value, but never
a side effect.
In general, a mulv can't be hoisted out of a loop that might have zero
iterations, but that is not apparent when you have a LIBCALL / RETVAL
sequence with only a REG_EQUAL note to describe the computation.