[PowerPC] SCV system call instruction missing

[edelsohn]

PPCInstrInfo.td defines the original SC system call instruction. The SCV system call instruction added in Power9 is not defined or available. The missing Power9 instruction is not mentioned in the README_P9.txt file of improvements.

The inability of Clang to recognize the SCV instruction in inline assembly prevents Clang from compiling some common Linux tools and packages, such as Valgrind.

[llvmbot]

@llvm/issue-subscribers-backend-powerpc

[edelsohn]

@tstellar FYI

[stefanp-synopsys]

I've put up a quick patch for this: #68063

[stefanp-synopsys]

This patch has now gone in:

commit 23e7da8f106e173f6efeaf7b791418b9494ac10c
Author: Stefan Pintilie <57511600+stefanp-ibm@users.noreply.github.com>
Date:   Thu Oct 5 12:51:04 2023 -0400

    [PowerPC] Add the SCV instruction. (#68063)
    
    The SCV instruciton was added on PowerPC on Power 9. This patch adds the
    SCV so that it may be used as part of inline asm but does not provide
    patterns for it or scheduling information.
    
    Co-authored-by: Stefan Pintilie <stefanp@ca.ibm.com>

[stefanp-synopsys]

@edelsohn
I believe that the fix has gone in at this point. Can this issue be closed?

[edelsohn]

Fixed.