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  <cltang@codesourcery.com>
	    Richard Earnshaw  <rearnsha@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.