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
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@348566 91177308-0d34-0410-b5e6-96231b3b80d8
Because the initial-value constants had not been added to the list
of instructions considered for DCE the resulting code had redundant
constant-materialization instructions.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177294 91177308-0d34-0410-b5e6-96231b3b80d8
Zi Xuan Wu