BitVector::resize does not initialize all new bits

[llvmbot]

Bugzilla Link	1563
Resolution	FIXED
Resolved on	Aug 06, 2007 15:56
Version	unspecified
OS	MacOS X
Reporter	LLVM Bugzilla Contributor

Extended Description

When resizing a BitVector that does not cause new allocations (say, resizing from 16 to 20 bits),
BitVector::resize fails to initial the four bits that are now being used. This can lead to inappropriate
behavior, and is preventing GVNPRE from using BitVectors are aggressively as would be possible.

[llvmbot]

assigned to @chandlerc

[chandlerc]

Patch to resolve BitVector resizing bugs.
Ok, this is a potential patch to resolve the resizing bugs in BitVector. It fixes one place where the BitWord type was not used, as well as ensuring both high words and high bits of the last used word are cleared. Lastly, it enables initializing the high words and high bits of the last used word when resizing already sized BitVectors. Does this look like it will solve the problems?

-Chandler

[chandlerc]

Version two af the above.
Accounted better for resizing down as well as up. Added logic to only set bits that need it, but to always set them when they are needed. Removed an extraneous call.

[chandlerc]

This is resolved with [40871].