6.16 gcc omit-frame pointer

Bruce Dubbs bruce.dubbs at gmail.com
Wed Dec 1 12:50:17 PST 2010


David Jensen wrote:
> On Wed, 01 Dec 2010 11:38:06 -0600
> Bruce Dubbs <bruce.dubbs at gmail.com> wrote:
> 
>> David Jensen wrote:
>>
>>> The point of the thread is that the 'chapter 5 gcc pass 2' and the
>>> 'chapter 6 gcc' instructions and explanations are inconsistent,
>>> confusing and wrong for all but i?86.  Maybe even completely
>>> outdated.
>> I'm not an expert on compilers, but the GCC instructions in Chapter 5 
>> and Chapter 6 need to be different for our purposes.
>>
>> What we have now works.  I'm reluctant to change the instructions on 
>> such an important component unless there are clear advantages.
>>
>>    -- Bruce
> 
> Well, maybe I'm nitpicking but 'chapter 5 gcc pass 2' says if you have
> an x86 do this, while 'chapter 6 gcc' says for consistency do something
> else.  The 'chapter 6 gcc' instructions do not work to give
> consistency on x86_64.  IMHO

In Chapter 5, we are not doing a full bootstrap, so we add 
-fomit-frame-pointer so it will produce the same codes as if it was a 
full bootstrap.

In Chapter 6, we do the same thing.  I think, but I'm not sure, that 
-fomit-frame-pointer is the default for x86_64.  If this is correct, 
perhaps we can tweak the text a little to clarify.

OTOH, it may not hurt anything to just add the flag unconditionally in 
Chapter 6 by removing the case statement.

   -- Bruce



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