Revert: r296141 [APInt] Add APInt::extractBits() method to extract APInt subrange

Revert: r296141 [APInt] Add APInt::extractBits() method to extract APInt subrange

The current pattern for extract bits in range is typically:

Mask.lshr(BitOffset).trunc(SubSizeInBits);

Which can be particularly slow for large APInts (MaskSizeInBits > 64) as they require the allocation of memory for the temporary variable.

This is another of the compile time issues identified in PR32037 (see also D30265).

This patch adds the APInt::extractBits() helper method which avoids the temporary memory allocation.

Differential Revision: https://reviews.llvm.org/D30336

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@296147 91177308-0d34-0410-b5e6-96231b3b80d8