On Sat, Apr 11, 2009 at 01:40:57AM +0100, Dave Korn wrote: > Stelian Pop wrote: > > >>> Do I need to define movsi3(), addsi3() etc. patterns manually or should > >>> GCC > >>> figure those by itself ? > >> Not sure I understand you. You always need to define movMM3 etc. GCC > >> will > >> correctly select between movhi3 and movsi3 based on your Pmode macro when > >> handling pointers, but you still need to write the patterns. > > > > The thing is that this CPU does not have any real 32 bit registers, or > > instructions to do assignments/additions/etc to 32 bit registers. So the 32 > > bit > > operations (on pointers) need to be emulated using the 16 bit components, > > and I > > thought that GCC can do this automatically for me ... > > Ah. In theory GCC should move everything by pieces. In practice, you have > to define mov patterns for SI and DI because rtl-level CSE isn't as smart as > it should be. You can use expanders for these.
Though if you use expanders that need temporary registers, you may have problems in reload, and need to delve into the mysteries of secondary reload. I would imagine that for pointer sized things it is best if you do need to implement multiple instructions that you hold off on splitting until after reload is completed. -- Michael Meissner, IBM 4 Technology Place Drive, MS 2203A, Westford, MA, 01886, USA meiss...@linux.vnet.ibm.com
