[LLVMbugs] [Bug 6155] Unneeded load not eliminated

bugzilla-daemon at cs.uiuc.edu bugzilla-daemon at cs.uiuc.edu
Tue Jan 26 23:43:46 PST 2010


http://llvm.org/bugs/show_bug.cgi?id=6155


Chris Lattner <clattner at apple.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |clattner at apple.com
             Status|NEW                         |RESOLVED
         Resolution|                            |INVALID




--- Comment #1 from Chris Lattner <clattner at apple.com>  2010-01-27 01:43:46 ---
You can see what is happening with:

$ opt -count-aa -gvn t.ll -S
May alias:      [4294967295B] i32* %stack1, [4294967295B] i32* %stack
May alias:      [4294967295B] i32* %stack1, [4294967295B] i32* %stack
...

Note that gvn is asking for an "unknown" size access.  This is because you
aren't specifying a target data, so it doesn't know how far apart stack1 is
from stack.  If you slap on a targetdata string, it is optimized properly.


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