#2662: gcc 4.5.0 -Os does not generate correct code
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Reporter: bdu...@… | Owner: lfs-b...@…
Type: defect | Status: new
Priority: high | Milestone: 6.7
Component: Book | Version: SVN
Severity: major | Keywords:
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Comment(by bdu...@…):
Replying to [comment:2 matt...@…]:
> What I'm thinking is if you could change the Kernel Makefile to set '-Os
-fno-<optimzation option>' instead of plain '-Os' to selectively turn off
individual optimization options that are explicitly mentioned in the
manual as being turned on by '-Os'. I realise that this is probably going
to be a fair bit of work unless you hit really lucky, so understand if you
don't want to expend that effort.
What I have to do to test this in the kernel is to remove the offending .o
file, change the Makefile and remake the kernel. That wouldn't be too
bad, but each test requires rebooting. Because I don't have an emulator
on the target system, a crash means that I have to power cycle.
I suppose I could do:
-Os -fno<option1> -fno<option2> ...
Which should work if I disable all the options. Then removing the no from
the options one at a time should work each time until I get to the problem
option.
From my reading, I suspect either -finline-small-functions or -findirect-
inlining
Even that technique concerns me because of the statement "-Os enables all
-O2 optimizations that do not typically increase code size. It also
performs further optimizations designed to reduce code size."
I don't know what the "further" optimizations are.
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Ticket URL: <http://wiki.linuxfromscratch.org/lfs/ticket/2662#comment:3>
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