8277617: Adjust AVX3Threshold for copy/fill stubs

Reviewed-by: jbhateja, dholmes, neliasso, jiefu

src/hotspot/cpu/x86/macroAssembler_x86.cpp

@@ -5021,7 +5021,7 @@ void MacroAssembler::xmm_clear_mem(Register base, Register cnt, Register rtmp, X
   // cnt - number of qwords (8-byte words).
   // base - start address, qword aligned.
   Label L_zero_64_bytes, L_loop, L_sloop, L_tail, L_end;
-  bool use64byteVector = MaxVectorSize == 64 && AVX3Threshold == 0;
+  bool use64byteVector = (MaxVectorSize == 64) && (VM_Version::avx3_threshold() == 0);
   if (use64byteVector) {
     vpxor(xtmp, xtmp, xtmp, AVX_512bit);
   } else if (MaxVectorSize >= 32) {
@@ -5085,7 +5085,7 @@ void MacroAssembler::xmm_clear_mem(Register base, Register cnt, Register rtmp, X
 // Clearing constant sized memory using YMM/ZMM registers.
 void MacroAssembler::clear_mem(Register base, int cnt, Register rtmp, XMMRegister xtmp, KRegister mask) {
   assert(UseAVX > 2 && VM_Version::supports_avx512vlbw(), "");
-  bool use64byteVector = MaxVectorSize > 32 && AVX3Threshold == 0;
+  bool use64byteVector = (MaxVectorSize > 32) && (VM_Version::avx3_threshold() == 0);
 
   int vector64_count = (cnt & (~0x7)) >> 3;
   cnt = cnt & 0x7;
@@ -5328,8 +5328,8 @@ void MacroAssembler::generate_fill(BasicType t, bool aligned,
           // Fill 64-byte chunks
           Label L_fill_64_bytes_loop_avx3, L_check_fill_64_bytes_avx2;
 
-          // If number of bytes to fill < AVX3Threshold, perform fill using AVX2
-          cmpl(count, AVX3Threshold);
+          // If number of bytes to fill < VM_Version::avx3_threshold(), perform fill using AVX2
+          cmpl(count, VM_Version::avx3_threshold());
           jccb(Assembler::below, L_check_fill_64_bytes_avx2);
 
           vpbroadcastd(xtmp, xtmp, Assembler::AVX_512bit);
@@ -8717,6 +8717,7 @@ void MacroAssembler::generate_fill_avx3(BasicType type, Register to, Register va
   Label L_fill_zmm_sequence;
 
   int shift = -1;
+  int avx3threshold = VM_Version::avx3_threshold();
   switch(type) {
     case T_BYTE:  shift = 0;
       break;
@@ -8732,10 +8733,10 @@ void MacroAssembler::generate_fill_avx3(BasicType type, Register to, Register va
       fatal("Unhandled type: %s\n", type2name(type));
   }
 
-  if (AVX3Threshold != 0  || MaxVectorSize == 32) {
+  if ((avx3threshold != 0)  || (MaxVectorSize == 32)) {
 
     if (MaxVectorSize == 64) {
-      cmpq(count, AVX3Threshold >> shift);
+      cmpq(count, avx3threshold >> shift);
       jcc(Assembler::greater, L_fill_zmm_sequence);
     }
 

src/hotspot/cpu/x86/macroAssembler_x86_arrayCopy_avx3.cpp

@@ -114,7 +114,7 @@ void MacroAssembler::arraycopy_avx3_special_cases_conjoint(XMMRegister xmm, KReg
                                                            bool use64byteVector, Label& L_entry, Label& L_exit) {
   Label L_entry_64, L_entry_96, L_entry_128;
   Label L_entry_160, L_entry_192;
-  bool avx3 = MaxVectorSize > 32 && AVX3Threshold == 0;
+  bool avx3 = (MaxVectorSize > 32) && (VM_Version::avx3_threshold() == 0);
 
   int size_mat[][6] = {
   /* T_BYTE */ {32 , 64,  96 , 128 , 160 , 192 },

src/hotspot/cpu/x86/stubGenerator_x86_64.cpp

@@ -1384,8 +1384,8 @@ class StubGenerator: public StubCodeGenerator {
     __ align(CodeEntryAlignment);
     StubCodeMark mark(this, "StubRoutines", name);
     address start = __ pc();
-
-    bool use64byteVector = MaxVectorSize > 32 && AVX3Threshold == 0;
+    int avx3threshold = VM_Version::avx3_threshold();
+    bool use64byteVector = (MaxVectorSize > 32) && (avx3threshold == 0);
     Label L_main_loop, L_main_loop_64bytes, L_tail, L_tail64, L_exit, L_entry;
     Label L_repmovs, L_main_pre_loop, L_main_pre_loop_64bytes, L_pre_main_post_64;
     const Register from        = rdi;  // source array address
@@ -1448,7 +1448,7 @@ class StubGenerator: public StubCodeGenerator {
       // PRE-MAIN-POST loop for aligned copy.
       __ BIND(L_entry);
 
-      if (AVX3Threshold != 0) {
+      if (avx3threshold != 0) {
         __ cmpq(count, threshold[shift]);
         if (MaxVectorSize == 64) {
           // Copy using 64 byte vectors.
@@ -1460,7 +1460,7 @@ class StubGenerator: public StubCodeGenerator {
         }
       }
 
-      if (MaxVectorSize < 64  || AVX3Threshold != 0) {
+      if ((MaxVectorSize < 64)  || (avx3threshold != 0)) {
         // Partial copy to make dst address 32 byte aligned.
         __ movq(temp2, to);
         __ andq(temp2, 31);
@@ -1603,7 +1603,8 @@ class StubGenerator: public StubCodeGenerator {
     StubCodeMark mark(this, "StubRoutines", name);
     address start = __ pc();
 
-    bool use64byteVector = MaxVectorSize > 32 && AVX3Threshold == 0;
+    int avx3threshold = VM_Version::avx3_threshold();
+    bool use64byteVector = (MaxVectorSize > 32) && (avx3threshold == 0);
 
     Label L_main_pre_loop, L_main_pre_loop_64bytes, L_pre_main_post_64;
     Label L_main_loop, L_main_loop_64bytes, L_tail, L_tail64, L_exit, L_entry;
@@ -1668,12 +1669,12 @@ class StubGenerator: public StubCodeGenerator {
       // PRE-MAIN-POST loop for aligned copy.
       __ BIND(L_entry);
 
-      if (MaxVectorSize > 32 && AVX3Threshold != 0) {
+      if ((MaxVectorSize > 32) && (avx3threshold != 0)) {
         __ cmpq(temp1, threshold[shift]);
         __ jcc(Assembler::greaterEqual, L_pre_main_post_64);
       }
 
-      if (MaxVectorSize < 64  || AVX3Threshold != 0) {
+      if ((MaxVectorSize < 64)  || (avx3threshold != 0)) {
         // Partial copy to make dst address 32 byte aligned.
         __ leaq(temp2, Address(to, temp1, (Address::ScaleFactor)(shift), 0));
         __ andq(temp2, 31);

src/hotspot/cpu/x86/vm_version_x86.cpp

@@ -1878,6 +1878,17 @@ void VM_Version::check_virtualizations() {
   }
 }
 
+// avx3_threshold() sets the threshold at which 64-byte instructions are used
+// for implementing the array copy and clear operations.
+// The Intel platforms that supports the serialize instruction
+// has improved implementation of 64-byte load/stores and so the default
+// threshold is set to 0 for these platforms.
+int VM_Version::avx3_threshold() {
+  return (is_intel_family_core() &&
+          supports_serialize() &&
+          FLAG_IS_DEFAULT(AVX3Threshold)) ? 0 : AVX3Threshold;
+}
+
 void VM_Version::initialize() {
   ResourceMark rm;
   // Making this stub must be FIRST use of assembler

src/hotspot/cpu/x86/vm_version_x86.hpp

@@ -911,6 +911,8 @@ enum Extended_Family {
   static bool is_intel_skylake() { return is_intel_family_core() &&
                                           extended_cpu_model() == CPU_MODEL_SKYLAKE; }
 
+  static int avx3_threshold();
+
   static bool is_intel_tsc_synched_at_init()  {
     if (is_intel_family_core()) {
       uint32_t ext_model = extended_cpu_model();