Clean up the comments and doxygen for DataLayout.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220191 91177308-0d34-0410-b5e6-96231b3b80d8
Remove some completely superfluous trailing comments and clang-format
this header to remove numerous formatting inconsistencies that impede
making simple changes here without large diffs.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220192 91177308-0d34-0410-b5e6-96231b3b80d8
Switch the default DataLayout to be little endian, and make the variable
be BigEndian so the default can continue to be zero-initialized.

This is one of the prerequisites to making DataLayout a constant and
always available part of every module.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220193 91177308-0d34-0410-b5e6-96231b3b80d8
[Thumb] Fix crash in Thumb1RegisterInfo::rewriteFrameIndex

This function can, for some offsets from the SP, split one instruction
into two. Since it re-uses the original instruction as the first
instruction of the result, we need ensure its result register is not
marked as dead before we use it in the second instruction.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220194 91177308-0d34-0410-b5e6-96231b3b80d8