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From: "amker at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/62173] [5.0 regression] 64bit Arch can't ivopt while 32bit Arch can
Date: Tue, 27 Jan 2015 03:21:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62173

--- Comment #25 from amker at gcc dot gnu.org ---
(In reply to Jiong Wang from comment #24)
> (In reply to amker from comment #23)
> 
> partially agree.
> 
> at least for the single use case given by Seb, I think tree ivopt should do
> it. (I verified clang do ivopt correctly for the case)
> 
> for the rtl re-associate, it's a little bit painful from my experiment
> experiences. as it's not always good to reassociate virtual_frame + offset,
> we can only benefit if it's in loop, because the re-associate will increase
> register pressure, there will be situations that more callee-saved regs
> used, and finally we run into unncessary push/pop in pro/epilogue... and I
> haven't found a good place where we can safely re-use existed rtl info and
> do the rtl re-association as I am afraid rebuild those rtl info will cause
> compile time penalty.

Yes, The ivopt's issue that it doesn't treat "A[d]" as an address type iv use
should be fixed anyway.