Add population_count for scalar version

src/hotspot/cpu/riscv/macroAssembler_riscv.cpp

@@ -3611,6 +3611,35 @@ void MacroAssembler::check_klass_subtype_slow_path(Register sub_klass,
   bind(L_fallthrough);
 }
 
+void MacroAssembler::population_count(Register dst, Register src,
+                                      Register tmp1, Register tmp2) {
+  if (UsePopCountInstruction) {
+    cpop(dst, src);
+  } else {
+    assert_different_registers(src, tmp1, tmp2);
+    assert_different_registers(dst, tmp1, tmp2);
+    Label loop, done;
+
+    mv(tmp1, src);
+    // dst = 0;
+    // while(tmp1 != 0) {
+    //   dst++;
+    //   tmp1 &= (tmp1 - 1);
+    // }
+    mv(dst, zr);
+    beqz(tmp1, done);
+    {
+      bind(loop);
+      addi(dst, dst, 1);
+      mv(tmp2, tmp1);
+      addi(tmp2, tmp2, -1);
+      andr(tmp1, tmp1, tmp2);
+      bnez(tmp1, loop);
+    }
+    bind(done);
+  }
+}
+
 // Ensure that the inline code and the stub are using the same registers
 // as we need to call the stub from inline code when there is a collision
 // in the hashed lookup in the secondary supers array.
@@ -3667,7 +3696,7 @@ bool MacroAssembler::lookup_secondary_supers_table(Register r_sub_klass,
   // Get the first array index that can contain super_klass into r_array_index.
   if (bit != 0) {
     slli(r_array_index, r_bitmap, (Klass::SECONDARY_SUPERS_TABLE_MASK - bit));
-    cpop(r_array_index, r_array_index);
+    population_count(r_array_index, r_array_index, t0, tmp1);
   } else {
     mv(r_array_index, (u1)1);
   }

src/hotspot/cpu/riscv/macroAssembler_riscv.hpp

@@ -322,6 +322,8 @@ class MacroAssembler: public Assembler {
                                      Label* L_success,
                                      Label* L_failure);
 
+  void population_count(Register dst, Register src, Register tmp1, Register tmp2);
+
   // As above, but with a constant super_klass.
   // The result is in Register result, not the condition codes.
   bool lookup_secondary_supers_table(Register r_sub_klass,

src/hotspot/cpu/riscv/vm_version_riscv.cpp

@@ -203,15 +203,6 @@ void VM_Version::initialize() {
     FLAG_SET_DEFAULT(UsePopCountInstruction, false);
   }
 
-  if (!UsePopCountInstruction) {
-    if (UseSecondarySupersTable) {
-      if (!FLAG_IS_DEFAULT(UseSecondarySupersTable)) {
-        warning("UseSecondarySupersTable is not supported on this CPU");
-      }
-      FLAG_SET_DEFAULT(UseSecondarySupersTable, false);
-    }
-  }
-
   if (UseZicboz) {
     if (FLAG_IS_DEFAULT(UseBlockZeroing)) {
       FLAG_SET_DEFAULT(UseBlockZeroing, true);