[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[hjl dot tools at gmail dot com]

------- Comment #32 from hjl dot tools at gmail dot com  2010-02-17 17:09 -------
(In reply to comment #31)
> I still have no idea what this PR is about.  Someone needs to make a clear
> statement of what they believe the ABI to be.  There are some simple questions:
> 
> * Can we expect that the stack is 16-byte aligned, or not?

Not if we want to be binary compatible with object files compiled by
compilers, including gcc 1.x/2.x/3.x, which generate 4byte stack alignment.

> 
> * If we cannot (because of legacy requirements), then is there any reason to
> try to align the stack automatically at entry to every function, or at every
> call site?  I can see that this might be useful as an option, but it does not
> seem like a sensible default to me.
> 

See PR 40838.  "-mstackrealign" now aligns the stack only if SSE vector
instructions are used in the function. The performance impact of
"-mstackrealign" is minimum:

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40838#c65


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156