Working secondary supers table with -XX:+UsePopCountInstruction

zifeihan · May 24, 2024 · f77598f · f77598f
1 parent e1187df
commit f77598f
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Showing 3 changed files with 11 additions and 35 deletions.
diff --git a/src/hotspot/cpu/riscv/macroAssembler_riscv.cpp b/src/hotspot/cpu/riscv/macroAssembler_riscv.cpp
@@ -3382,36 +3382,6 @@ void MacroAssembler::check_klass_subtype_slow_path(Register sub_klass,
   bind(L_fallthrough);
 }
 
-void MacroAssembler::population_count(Register dst, Register src,
-                                      Register temp1, Register temp2) {
-
-  if (UsePopCountInstruction) {
-    cpop(dst, src);
-  } else {
-    assert_different_registers(src, temp1, temp2);
-    assert_different_registers(dst, temp1, temp2);
-    Label loop, done;
-
-    mv(temp1, src);
-    // dst = 0;
-    // while(temp1 != 0) {
-    //   dst++;
-    //   temp1 &= (temp1 - 1);
-    // }
-    mv(dst, zr);
-    beqz(temp1, done);
-    {
-      bind(loop);
-      addi(dst, dst, 1);
-      mv(temp2, temp1);
-      addi(temp2, temp2, -1);
-      andr(temp1, temp1, temp2);
-      bnez(temp1, loop);
-    }
-    bind(done);
-  }
-}
-
 // Ensure that the inline code and the stub are using the same registers.
 #define LOOKUP_SECONDARY_SUPERS_TABLE_REGISTERS                    \
 do {                                                               \
@@ -3463,7 +3433,7 @@ 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));
-    population_count(r_array_index, r_array_index, t0, temp1);
+    cpop(r_array_index, r_array_index);
   } else {
     mv(r_array_index, (u1)1);
   }
@@ -3624,8 +3594,7 @@ void MacroAssembler::verify_secondary_supers_table(Register r_sub_klass,
   // And adjust the array base to point to the data.
   addi(r_array_base, r_array_base, Array<Klass*>::base_offset_in_bytes());
 
-  repne_scan(r_array_base, r_super_klass, r_array_length, t1);
-  mv(t0, t1);
+  repne_scan(r_array_base, r_super_klass, r_array_length, t0);
   Label success;
   beq(r_super_klass, t0, success);
   mv(t0, zr);

diff --git a/src/hotspot/cpu/riscv/macroAssembler_riscv.hpp b/src/hotspot/cpu/riscv/macroAssembler_riscv.hpp
@@ -322,8 +322,6 @@ class MacroAssembler: public Assembler {
                                      Label* L_success,
                                      Label* L_failure);
 
-  void population_count(Register dst, Register src, Register temp1, Register temp2);
-
   // 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,

diff --git a/src/hotspot/cpu/riscv/vm_version_riscv.cpp b/src/hotspot/cpu/riscv/vm_version_riscv.cpp
@@ -203,6 +203,15 @@ 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);