[x64][win] Bad codegen with -import-call-optimization

[SEt-t]

I was excited to see new optimization option for library calls, but currently (21.1.0-rc1) it produces broken code:
https://godbolt.org/z/TazjTxfdz

It does generate REX-CALL and NOP, but

1. CALL type is wrong (relative instead of indirect).
2. NOP is slightly different to the one generated by MSVC: 0F 1F 44 00 08 instead of 0F 1F 44 00 00. Not sure if this is important to system loader or not.

[llvmbot]

@llvm/issue-subscribers-backend-x86

Author: SEt (SEt-t)

I was excited to see new optimization option for library calls, but currently (21.1.0-rc1) it produces broken code: https://godbolt.org/z/TazjTxfdz

It does generate REX-CALL and NOP, but

1. CALL type is wrong (relative instead of indirect).
2. NOP is slightly different to the one generated by MSVC: 0F 1F 44 00 08 instead of 0F 1F 44 00 00. Not sure if this is important to system loader or not.