On Fri, 2011-04-08 at 15:52 +0800, Chung-Lin Tang wrote: > Hi Richard, > here's a new patch, with some quite significant changes to > arm_legitimize_reload_address(). This time fully utilizing the > sign-magnitude offset macro you gave in the last thread, and adapting > your description into embedded comments. > > The reload_outdf pattern caused some regressions in a first round of > testing. With the new reload address legitimization, which creates a RTX > like (mem (plus (plus reg #high) #low)), the current > SECONDARY_RELOAD_OUTPUT_CLASS macro returns 'GENERAL_REGS' under VFP, > which triggers the execution of reload_outdf, but now creating > unexpected (set (reg1) (plus (plus reg #high) #low)) insns. > > The historical reasons for the reload_outdf pattern are not entirely > clear, as we discussed off list. In any case, we should aim to update > the ARM secondary reload stuff to use the newer framework. I have > disabled the pattern under ARM mode, and cross-tested the entire patch > under v7-A/v5TE VFP, v7-A NEON, and v4T soft-float configs, all clear of > regressions. > > reload_outdf is disabled by changing the pattern condition from > TARGET_32BIT to TARGET_THUMB2 (disabling TARGET_ARM only). This is > temporary, Thumb-2 probably needs a few more bits of simultaneous > updates to work, so I'm leaving that for a later patch. > > I've listed your name together as significant parts are from you. Is it > ready for trunk? > > Thanks, > Chung-Lin > > 2011-04-08 Chung-Lin Tang <clt...@codesourcery.com> > Richard Earnshaw <rearn...@arm.com> > > PR target/48250 > * config/arm/arm.c (arm_legitimize_reload_address): Update cases > to use sign-magnitude offsets. Reject unsupported unaligned > cases. Add detailed description in comments. > * config/arm/arm.md (reload_outdf): Disable for ARM mode; change > condition from TARGET_32BIT to TARGET_ARM.
This is OK, thanks for working on it. Nothing to do with this patch specifically, but I'll note here for completeness that LEGITIMIZE_RELOAD_ADDRESS is missing some fundamental information which makes generating optimal code here impossible: there's no information available about what the address is going to be used for. Given that the set of legitimate addresses depends on this is, IMO, a fundamental problem. R.
