Accelerate StringCoding.countPositives on Z

[dchopra001]

This PR accelerates the StringCoding.countPositives API on z/codegen for JDK21+. This API is similar in implementation to the recently accelerated StringCoding.hasNegatives API so we leverage the existing implementation to add acceleration for StringCoding.countPositives as well.

[r30shah]

Overall looks ok to me (Structure wise). Please add short description to commit.

I will give detail review once you confirm passing of functional tests. Also Can I request you to share the instruction selection snippet ?

[dchopra001]

Instruction Log:

============================================================
; Live regs: GPR=3 FPR=0 VRF=0 {&GPR_0034, GPR_0033, GPR_0032}
------------------------------
 n7n      (  0)  treetop                                                                              [     0x3ff56c82880] bci=[-1,3,79] rc=0 vc=207 vn=- li=2 udi=- nc=1
 n6n      (  2)    icall  java/lang/StringCoding.countPositives([BII)I[#405  static Method] [flags 0x500 0x0 ] ()  [     0x3ff56c82830] bci=[-1,3,79] rc=2 vc=207 vn=- li=2 udi=- nc=3 flg=0x20
 n44n     (  1)      ==>aRegLoad (in &GPR_0034) (SeenRealReference )
 n43n     (  1)      ==>iRegLoad (in GPR_0033) (cannotOverflow SeenRealReference )
 n42n     (  1)      ==>iRegLoad (in GPR_0032) (cannotOverflow SeenRealReference )
------------------------------
------------------------------
 n7n      (  0)  treetop                                                                              [     0x3ff56c82880] bci=[-1,3,79] rc=0 vc=207 vn=- li=2 udi=- nc=1
 n6n      (  1)    icall  java/lang/StringCoding.countPositives([BII)I[#405  static Method] [flags 0x500 0x0 ] (in GPR_0041) ()  [     0x3ff56c82830] bci=[-1,3,79] rc=1 vc=207 vn=- li=2 udi=- nc=3 flg=0x20
 n44n     (  0)      ==>aRegLoad (in &GPR_0034) (SeenRealReference )
 n43n     (  0)      ==>iRegLoad (in GPR_0033) (cannotOverflow SeenRealReference )
 n42n     (  0)      ==>iRegLoad (in GPR_0032) (cannotOverflow SeenRealReference )
------------------------------

 [     0x3ff56d60e80]                          LR      GPR_0041,GPR_0032
 [     0x3ff56e1e000]                          Label L0035:     # (Start of internal control flow)
 [     0x3ff56e1e0e0]                          CIJ     GPR_0032,Label L0034,0,BH(mask=0x8),
 [     0x3ff56e1e1d0]                          AGFR    &GPR_0034,GPR_0033
 [     0x3ff56e1e2b0]                          LR      GPR_0038,GPR_0032
 [     0x3ff56e1e390]                          VREPIB  VRF_0036,0x7f
 [     0x3ff56e1e480]                          VREPIB  VRF_0037,0x20
 [     0x3ff56e1e570]                          CIJ     GPR_0038,Label L0033,16,BNL(mask=0xc),
 [     0x3ff56e1e660]                          Label L0032:
 [     0x3ff56e1e800]                          VL      VRF_0035,#407 8(&GPR_0034),0
 [     0x3ff56e1e8e0]                          VSTRCBS VRF_0039,VRF_0035,VRF_0036,VRF_0037,1
 [     0x3ff56e1e9c0]                          BRC     MASK5(0x4), Label L0036
 [     0x3ff56e1eb60]                          LA      &GPR_0034,#408 16(&GPR_0034)
 [     0x3ff56e1ec30]                          AHI     GPR_0038,0xfff0
 [     0x3ff56e1ed10]                          CIJ     GPR_0038,Label L0032,16,BL(mask=0x2),
 [     0x3ff56e1ee00]                          Label L0033:
 [     0x3ff56e1eee0]                          VGBM    VRF_0035,0x0
 [     0x3ff56e1efd0]                          AHI     GPR_0038,0xffff
 [     0x3ff56e1f170]                          VLL     VRF_0035,GPR_0038,#409 8(&GPR_0034)
 [     0x3ff56e1f250]                          VSTRCBS VRF_0039,VRF_0035,VRF_0036,VRF_0037,1
 [     0x3ff56e1f330]                          BRC     MASK5(0x4), Label L0037
 [     0x3ff56e1f410]                          BRC     NOP(0xf), Label L0034
 [     0x3ff56e1f4f0]                          Label L0037:
 [     0x3ff56e1f5d0]                          AHI     GPR_0038,0x1
 [     0x3ff56e1f6b0]                          Label L0036:
 [     0x3ff56e1f790]                          SRK     GPR_0041,GPR_0032,GPR_0038
 [     0x3ff56e1f930]                          VLGVB   GPR_0040,VRF_0039,#410 7
 [     0x3ff56e1fa10]                          AR      GPR_0041,GPR_0040
 [     0x3ff56e20200]                          assocreg
 [     0x3ff56e1fc40]                          Label L0034:     # (End of internal control flow)
 POST:
 {AssignAny:GPR_0040:R} {AssignAny:GPR_0032:R} {AssignAny:VRF_0035:R} {AssignAny:VRF_0039:R} {AssignAny:VRF_0036:R} {AssignAny:VRF_0037:R} {AssignAny:&GPR_0034:R} {AssignAny:GPR_0038:R}
 {AssignAny:GPR_0041:R} {AssignAny:GPR_0033:R}

[dchopra001]

@r30shah Sanity build is clean now so this is ready for detailed review. The instruction log I posted earlier is consistent with the latest changes.