On 13 November 2006 12:37, Dave Korn wrote:
> You *must* implement a movdi expander, and it has to be clever enough to
> notice when one of the output registers is going to clobber one of the input
> operands and emit the two SImode halves of the move in the opposite order.
Take a look at, e.g., rs6000.md, the way that movdi is an expander that
calls rs6000_emit_move to emit a (set (xxx:DI ) (xxx:DI)) which is then
recognized by *movdi_internal32 which takes care to emit two SI-sized move
opcodes in the right order.
Doing this also avoids a bug in the interpretation of REG_EQUAL notes when
applied to SI mode SUBREGs of DI mode REGs during cse, at least in 3.3.3 it
does.
cheers,
DaveK
--
Can't think of a witty .sigline today....
