hotspot/src/cpu/x86/vm/stubGenerator_x86_64.cpp

rev 7347 : 8078113: 8011102 changes may cause incorrect results
Summary: replace Vzeroupper instruction in stubs with zeroing only used ymm registers.
Reviewed-by: kvn
Contributed-by: sandhya.viswanathan@intel.com

*** 1326,1336 ****
        }
        __ addptr(qword_count, 4);
        __ BIND(L_end);
        if (UseAVX >= 2) {
          // clean upper bits of YMM registers
!         __ vzeroupper();
        }
      } else {
        // Copy 32-bytes per iteration
        __ BIND(L_loop);
        __ movq(to, Address(end_from, qword_count, Address::times_8, -24));
--- 1326,1337 ----
        }
        __ addptr(qword_count, 4);
        __ BIND(L_end);
        if (UseAVX >= 2) {
          // clean upper bits of YMM registers
!         __ vpxor(xmm0, xmm0);
!         __ vpxor(xmm1, xmm1);
        }
      } else {
        // Copy 32-bytes per iteration
        __ BIND(L_loop);
        __ movq(to, Address(end_from, qword_count, Address::times_8, -24));
*** 1403,1413 ****
        }
        __ subptr(qword_count, 4);
        __ BIND(L_end);
        if (UseAVX >= 2) {
          // clean upper bits of YMM registers
!         __ vzeroupper();
        }
      } else {
        // Copy 32-bytes per iteration
        __ BIND(L_loop);
        __ movq(to, Address(from, qword_count, Address::times_8, 24));
--- 1404,1415 ----
        }
        __ subptr(qword_count, 4);
        __ BIND(L_end);
        if (UseAVX >= 2) {
          // clean upper bits of YMM registers
!         __ vpxor(xmm0, xmm0);
!         __ vpxor(xmm1, xmm1);
        }
      } else {
        // Copy 32-bytes per iteration
        __ BIND(L_loop);
        __ movq(to, Address(from, qword_count, Address::times_8, 24));