From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Michael P. Hayes" <michaelh@ongaonga.chch.cri.nz>
To: egcs@cygnus.com
Subject: Reloading index register
Date: Fri, 17 Oct 1997 19:23:00 -0000
Message-id: <199710180228.PAA27273@ongaonga.chch.cri.nz>
X-SW-Source: 1997-10/msg00769.html

Can anybody who understands the reload pass enlighten me why it
generates,

(set (reg index2) (reg dud))
(set (reg index2) (mem (plus (reg base2) (reg index2))))
(set (reg r0) (minus (mem (plus (reg base1) (reg index1)))
                     (reg index2)))

instead of the better code,

(set (reg index2) (reg dud))
(set (reg r0) (minus (mem (plus (reg base1) (reg index1)))
                     (mem (plus (reg base2) (reg index2)))))

for the code fragment,

(set (reg r0) (minus (mem (plus (reg base1) (reg index1)))
                     (mem (plus (reg base2) (reg dud)))))

where the global register allocator couldn't assign reg dud to an
index register and so reload spills index register index2 to obtain a
reload register.