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  1. Qt
  2. QTBUG-58647

qPopulationCount uses unchecked SSE4 instructions with MSVC

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    Details

    • Type: Bug
    • Status: Closed
    • Priority: P1: Critical
    • Resolution: Duplicate
    • Affects Version/s: 5.8, 5.9.0 Alpha
    • Fix Version/s: 5.9.0 Alpha
    • Component/s: Core: Containers and Algorithms
    • Labels:
      None
    • Environment:
      WIndows 10 64bit MSVC2015 U3 64bit

      Description

      With qtdeclarative/5.9 at b7090f1334ac7b8ad2548f084c749eda4fa82451 , Qt Core at f3b3e79feb64e57c2f0ab7030080920c338fd99e:

      • Launch samegame, press Exit button
      • Note crash

      Note: Qt Creator 4.2 also crashes with a similar stack trace.

      This is due to the use of qPopulationCount, which - when using MSVC intrinsics - expands to an SSE 4 instruction that requires CPUID checking at run-time. No such checking is done though.

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          is duplicated by

          Bug - A problem which impairs or prevents the functions of the product. QTBUG-58446 [REG 5.7→5.8] Illegal instruction POPCNT

          • P1: Critical - Urgent and Important, will STOP the release if matched with set FixVersion field. This includes regressions from the last version that are not edge cases; Data loss; Build issues; All but the most unlikely crashes/lockups/hanging; Serious usability issues and embarrassing bugs & Bugs critical to a deliverable. This is the highest possible priority for requirements.
          • Closed
          relates to

          Bug - A problem which impairs or prevents the functions of the product. QTBUG-58446 [REG 5.7→5.8] Illegal instruction POPCNT

          • P1: Critical - Urgent and Important, will STOP the release if matched with set FixVersion field. This includes regressions from the last version that are not edge cases; Data loss; Build issues; All but the most unlikely crashes/lockups/hanging; Serious usability issues and embarrassing bugs & Bugs critical to a deliverable. This is the highest possible priority for requirements.
          • Closed
          For Gerrit Dashboard: QTBUG-58647
          # Subject Branch Project Status CR V
          184718,1 Disable the use of MSVC's __popcnt intrinsic for qPopulationCount 5.8 qt/qtbase Status: ABANDONED 0 0

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              Assignee:
              shausman Simon Hausmann
              Reporter:
              kleint Friedemann Kleint
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                Dates

                Created:
                Updated:
                Resolved:

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