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Re: divide 64-bit by constant for 32-bit target machines

From: Dinar Temirbulatov <dtemirbulatov at gmail dot com>
To: Michael Hope <michael dot hope at linaro dot org>
Cc: gcc-patches at gcc dot gnu dot org, aph at redhat dot com
Date: Thu, 3 May 2012 14:27:59 +0400
Subject: Re: divide 64-bit by constant for 32-bit target machines
References: <CAMnfPmPi9U9E=ntqYx1vdsC3E+6XZ7isTk4vdXLDD02xT_n-4g@mail.gmail.com> <CANLjY-mOtYW54RQuQVxGdiS_BB4WTYbDp5RhfAEgTu-gTKKc+A@mail.gmail.com>

Hi,
Here is updated version of patch. I added comments describing the algorithm.

> Hi Dinar. ?I'm afraid it gives the wrong results for some dividends
> ?* 82625484914982912 / 2023346444509052928: gives 4096, should be zero
> ?* 18317463604061229328 / 2023346444509052928: gives 4109, should be 9
> ?* 12097415865295708879 / 4545815675034402816: gives 130, should be 2
> ?* 18195490362097456014 / 6999635335417036800: gives 10, should be 2
Oh, I have used signed multiplication instead of unsigned and that was
the reason of errors above, fixed that typo.
Tested on arm-7l with no new regressions.
Ok for trunk?

thanks, Dinar.

Attachment: 14.patch
Description: Binary data

Follow-Ups:
- Re: divide 64-bit by constant for 32-bit target machines
  - From: Richard Earnshaw

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