Hack to workaround a clang lto bug #6782
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We hit an assert in AllocStackHoisting that is only triggered in a release lto build. Clang forwards the read of parent basic block of 'AssignedLoc' in the next statement: auto *EntryBB = AssignedLoc->getFunction()->getEntryBlock(); // read AssignedLoc->ParentBB AssignedLoc->removeFromParent(); // writes AssignedLoc->ParentBB To this read: EntryBB->push_front(AssignedLoc); // read AssignedLoc->ParentBB and assert if non-null, *should reload* As a temporary workaround outline code to prevent the miscompile. rdar://29982182
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@swift-ci Please smoke test |
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@swift-ci Please smoke test |
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@swiftix Can you review for swift-3.1-branch? |
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@aschwaighofer LGTM! |
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We hit an assert in AllocStackHoisting that is only triggered in a release lto
build.
Clang forwards the read of parent basic block of 'AssignedLoc' in the next
statement:
auto *EntryBB = AssignedLoc->getFunction()->getEntryBlock(); // read AssignedLoc->ParentBB
AssignedLoc->removeFromParent(); // writes AssignedLoc->ParentBB
To this read:
EntryBB->push_front(AssignedLoc); // read AssignedLoc->ParentBB and assert if non-null, should reload
As a temporary workaround outline code to prevent the miscompile.
rdar://29982182