Fix optimisations of SELECT_CC which assumed result is boolean

Some optimisations in DAGCombiner cause miscompilations for targets that use
TargetLowering::UndefinedBooleanContent, because they assume that the results
of a SELECT_CC node are boolean values, and can be safely ANDed, ORed and
XORed. These optimisations are only valid for targets that use
ZeroOrOneBooleanContent or ZeroOrNegativeOneBooleanContent.

This is a follow-up to D6210/r221693.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222123 91177308-0d34-0410-b5e6-96231b3b80d8
Object, COFF: Tighten the object file parser

We were a little lax in a few areas:
- We pretended that import libraries were like any old COFF file, they
  are not.  In fact, they aren't really COFF files at all, we should
  probably grow some specialized functionality to handle them smarter.
- Our symbol iterators were more than happy to attempt to go past the
  end of the symbol table if you had a symbol with a bad list of
  auxiliary symbols.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222124 91177308-0d34-0410-b5e6-96231b3b80d8
[Thumb1] Re-write emitThumbRegPlusImmediate

This was motivated by a bug which caused code like this to be
miscompiled:
  declare void @take_ptr(i8*)
  define void @test() {
    %addr1.32 = alloca i8
    %addr2.32 = alloca i32, i32 1028
    call void @take_ptr(i8* %addr1)
    ret void
  }

This was emitting the following assembly to get the value of %addr1:
  add r0, sp, #1020
  add r0, r0, #8
However, "add r0, r0, #8" is not a valid Thumb1 instruction, and this
could not be assembled. The generated object file contained this,
resulting in r0 holding SP+8 rather tha SP+1028:
  add r0, sp, #1020
  add r0, sp, #8

This function looked like it could have caused miscompilations for
other combinations of registers and offsets (though I don't think it is
currently called with these), and the heuristic it used did not match
the emitted code in all cases.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222125 91177308-0d34-0410-b5e6-96231b3b80d8