From: Alan Lehotsky <apl@alum.mit.edu>
To: gcc@gcc.gnu.org
Subject: Why does peephole not handle JUMP before barrier?
Date: Wed, 12 Sep 2001 09:30:00 -0000 [thread overview]
Message-ID: <p04330103b7c53c924b45@[192.168.1.254]> (raw)
genpeep.c produces a peephole() function that explicitly excludes performing peepholes on
anything that's immediately followed by a barrier instruction.
I've got a machine that has branch delay slots. If the instruction following a branch is another branch,
then the second branch is suppressed. So, if I have something like
jeq $10
nop
jmp $12
....
that can be replaced by
jeq $10
jmp $12
...
avoiding the nop.
But, if I've got
jmp $10
nop
jmp $12
nop
the peephole() NEVER looks at the jmp $10, as it's actually got a barrier after it.
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