[LLVMbugs] [Bug 13615] APInt::udivrem says 1/1 == -1

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=13615

Benjamin Kramer <benny.kra at gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |benny.kra at gmail.com
         Resolution|                            |INVALID

--- Comment #1 from Benjamin Kramer <benny.kra at gmail.com> 2012-08-18 04:30:23 CDT ---
This is an artifact of the default APInt constructor. It creates an APInt with
bit width 1, and with that width 1 is equal to -1.

The right usage of udivrem is:

APInt a(32, 1), b(32, 1), c(32, 0), d(32, 0);
APInt::udivrem(a, b, c, d);
dbgs() << "dividing " << a << " by " << b << " yields " << c << " rem " << d <<
"\n";

and it prints:

dividing 1 by 1 yields 1 rem 0


I agree that it is very easy to misuse this API but I'm not sure how to fix it.

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