https://llvm.org/bugs/show_bug.cgi?id=25986
David Majnemer <david.majne...@gmail.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
CC| |david.majne...@gmail.com
Component|new bugs |Scalar Optimizations
Resolution|--- |INVALID
Product|new-bugs |libraries
--- Comment #1 from David Majnemer <david.majne...@gmail.com> ---
Hi Yuanrui,
I do not believe InstCombine is wrong here.
The value you chose for '%j' is 'i32 2147483647'.
The add instruction in '%inc' is 'add nsw i32 %j, 1'. Notice the 'nsw' flag on
the add instruction, it means that '%inc' is poison if it sign overflows or
sign underflows (see http://llvm.org/docs/LangRef.html#poisonvalues)
This means that we have the following dynamic values:
%j = i32 2147483647
%inc = i32 poison
%cmp = i1 poison
%conv = i32 poison
If you want signed overflow/underflow to be well defined, remove the nsw flag
from the add instruction.
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