8007708: compiler/6855215 assert(VM_Version::supports_sse4_2())

Summary: Added missing UseSSE42 check. Also added missing avx2 assert for vpermq instruction.
Reviewed-by: roland, twisti

src/cpu/x86/vm/assembler_x86.cpp

@@ -2270,6 +2270,7 @@ void Assembler::vpackuswb(XMMRegister dst, XMMRegister nds, XMMRegister src, boo
 }
 
 void Assembler::vpermq(XMMRegister dst, XMMRegister src, int imm8, bool vector256) {
+  assert(VM_Version::supports_avx2(), "");
   int encode = simd_prefix_and_encode(dst, xnoreg, src, VEX_SIMD_66, VEX_OPCODE_0F_3A, true, vector256);
   emit_int8(0x00);
   emit_int8(0xC0 | encode);

src/cpu/x86/vm/macroAssembler_x86.cpp

@@ -5691,7 +5691,7 @@ void MacroAssembler::string_compare(Register str1, Register str2,
   Address::ScaleFactor scale = Address::times_2;
   int stride = 8;
 
-  if (UseAVX >= 2) {
+  if (UseAVX >= 2 && UseSSE42Intrinsics) {
     Label COMPARE_WIDE_VECTORS, VECTOR_NOT_EQUAL, COMPARE_WIDE_TAIL, COMPARE_SMALL_STR;
     Label COMPARE_WIDE_VECTORS_LOOP, COMPARE_16_CHARS, COMPARE_INDEX_CHAR;
     Label COMPARE_TAIL_LONG;