On Wed, Mar 11, 2015 at 5:51 PM, David Wohlferd <d...@limegreensocks.com> wrote: > > The reason I believe the order can change is this comment from i386.h: > > /* Order in which to allocate registers. Each register must be > listed once, even those in FIXED_REGISTERS. List frame pointer > late and fixed registers last. Note that, in general, we prefer > registers listed in CALL_USED_REGISTERS, keeping the others > available for storage of persistent values. > > The ADJUST_REG_ALLOC_ORDER actually overwrite the order, > so this is just empty initializer for array. */
That is REG_ALLOC_ORDER. The index that appears in an asm statement is the hard register number. REG_ALLOC_ORDER is an array holding hard register numbers. The hard register numbers can change in principle, by changing the source code, but I actually can't recall that ever happening. Ian
