build: fix determinism issue when building qt with Clang 8 #20440
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fanquake
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…istic behavior in LLVM 8 8f7d1b3 Fix QPainter non-determinism on macOS (Andrew Chow) Pull request description: Aplies a patch to Qt that fixes the non-determinism by modifying Qt. The source of the non-determinism is how LLVM 8 optimizes qt_intersect_spans when compiling. The particular optimization that seems to be causing the problems is that a temp variable is being added for spans->y. For some reason, when it does this, it chooses different instructions to use when making that variable. We bypass this problem by patching qt_intersect_spans to always make and use this local variable. Potential alternative to #20436 and #20440 ACKs for top commit: hebasto: re-ACK 8f7d1b3 ~for merging into the 0.21 branch, but [not into the master](#20454) branch.~ fanquake: ACK 8f7d1b3 Tree-SHA512: b0d00a77643554021736524fb64611462ef2ec849a220543c12d99edb0f52f2e8128d2cc61fa82176b7e13b294574774a92d6b649badf8b7630c6d6a7e70ce10
sidhujag
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…eterministic behavior in LLVM 8 8f7d1b3 Fix QPainter non-determinism on macOS (Andrew Chow) Pull request description: Aplies a patch to Qt that fixes the non-determinism by modifying Qt. The source of the non-determinism is how LLVM 8 optimizes qt_intersect_spans when compiling. The particular optimization that seems to be causing the problems is that a temp variable is being added for spans->y. For some reason, when it does this, it chooses different instructions to use when making that variable. We bypass this problem by patching qt_intersect_spans to always make and use this local variable. Potential alternative to bitcoin#20436 and bitcoin#20440 ACKs for top commit: hebasto: re-ACK 8f7d1b3 ~for merging into the 0.21 branch, but [not into the master](bitcoin#20454) branch.~ fanquake: ACK 8f7d1b3 Tree-SHA512: b0d00a77643554021736524fb64611462ef2ec849a220543c12d99edb0f52f2e8128d2cc61fa82176b7e13b294574774a92d6b649badf8b7630c6d6a7e70ce10
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Potential alternative to #20436. This is a patch, rather than changes being
echo'd into thesrc/gui/Makefilepost configure. It's also scoped to just darwin. Changes are based offversiontagging_compilerin corelib/global/global.pri.From #20436:
I guess this is at the
qmakelevel, but still feels like a bit of a hack. If we decide to go this way will add Carl/Cory as co-authors.