Brad Boyer <flar@xxxxxxxxxxxxx> writes: > On Fri, Jul 03, 2009 at 12:14:41PM +0530, kernel mailz wrote: >> b. using m or Z with a memory address. I tried replacing m/Z but no change >> Is there some guideline ? >> gcc documentation says Z is obsolete. Is m/Z replaceable ? > > No idea. I don't remember ever seeing 'Z' used in anything. Maybe somebody > else remembers what it used to mean. The 'Z' constraint is required for a memory operand for insns that don't have an update form (which would be selected by the %U modifier). It should only be used together with the %y operand modifier, which makes sure that the first register is never 0. If the 'm' constraint were used the operand could contain a pre-in/decrement operation, and without %U the side effect would be lost. Andreas. -- Andreas Schwab, schwab@xxxxxxxxxxxxxx GPG Key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5 "And now for something completely different."
