Fix assert about using an undefined physical register in machine instruction verify pass.
The reason is that register flag undef is missing when doing transformation from If Conversion Pass.
```
Bad machine code: Using an undefined physical register
- function: func_65
- basic block: %bb.0 entry (0x10024740738)
- instruction: BCLR killed $cr5lt, implicit $lr8, implicit $rm, implicit undef $x3
- operand 0: killed $cr5lt
LLVM ERROR: Found 1 machine code errors.
```
There are also other existing testcases with same issue. So I add -verify-machineinstrs option to open verifying.
Differential Revision: https://reviews.llvm.org/D55408
llvm-svn: 348566
Although you can't generate this from C on PPC64, if you have a loop using a
64-bit counter on PPC32 then you can't form a CTR-based loop for it. This had
been cauing the PPCCTRLoops pass to assert.
Thanks to Joerg Sonnenberger for providing a test case!
llvm-svn: 185361
