diff -r ffa87474d7a4 -r 038dd2875b94 src/cpu/x86/vm/macroAssembler_x86.cpp
--- a/src/cpu/x86/vm/macroAssembler_x86.cpp	Mon Jan 07 14:08:28 2013 -0800
+++ b/src/cpu/x86/vm/macroAssembler_x86.cpp	Tue Jan 08 11:30:51 2013 -0800
@@ -5675,42 +5675,114 @@
   testl(cnt2, cnt2);
   jcc(Assembler::zero, LENGTH_DIFF_LABEL);
 
-  // Load first characters
+  // Compare first characters
   load_unsigned_short(result, Address(str1, 0));
   load_unsigned_short(cnt1, Address(str2, 0));
-
-  // Compare first characters
   subl(result, cnt1);
   jcc(Assembler::notZero,  POP_LABEL);
-  decrementl(cnt2);
-  jcc(Assembler::zero, LENGTH_DIFF_LABEL);
-
-  {
-    // Check after comparing first character to see if strings are equivalent
-    Label LSkip2;
-    // Check if the strings start at same location
-    cmpptr(str1, str2);
-    jccb(Assembler::notEqual, LSkip2);
-
-    // Check if the length difference is zero (from stack)
-    cmpl(Address(rsp, 0), 0x0);
-    jcc(Assembler::equal,  LENGTH_DIFF_LABEL);
-
-    // Strings might not be equivalent
-    bind(LSkip2);
-  }
+  cmpl(cnt2, 1);
+  jcc(Assembler::equal, LENGTH_DIFF_LABEL);
+
+  // Check if the strings start at the same location.
+  cmpptr(str1, str2);
+  jcc(Assembler::equal, LENGTH_DIFF_LABEL);
 
   Address::ScaleFactor scale = Address::times_2;
   int stride = 8;
 
-  // Advance to next element
-  addptr(str1, 16/stride);
-  addptr(str2, 16/stride);
-
-  if (UseSSE42Intrinsics) {
+  if (UseAVX >= 2) {
+    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;
+    int pcmpmask = 0x19;
+
+    // Setup to compare 16-chars (32-bytes) vectors,
+    // start from first character again because it has aligned address.
+    int stride2 = 16;
+    int adr_stride  = stride  << scale;
+    int adr_stride2 = stride2 << scale;
+
+    assert(result == rax && cnt2 == rdx && cnt1 == rcx, "pcmpestri");
+    // rax and rdx are used by pcmpestri as elements counters
+    movl(result, cnt2);
+    andl(cnt2, ~(stride2-1));   // cnt2 holds the vector count
+    jcc(Assembler::zero, COMPARE_TAIL_LONG);
+
+    // fast path : compare first 2 8-char vectors.
+    bind(COMPARE_16_CHARS);
+    movdqu(vec1, Address(str1, 0));
+    pcmpestri(vec1, Address(str2, 0), pcmpmask);
+    jccb(Assembler::below, COMPARE_INDEX_CHAR);
+
+    movdqu(vec1, Address(str1, adr_stride));
+    pcmpestri(vec1, Address(str2, adr_stride), pcmpmask);
+    jccb(Assembler::aboveEqual, COMPARE_WIDE_VECTORS);
+    addl(cnt1, stride);
+
+    // Compare the characters at index in cnt1
+    bind(COMPARE_INDEX_CHAR); //cnt1 has the offset of the mismatching character
+    load_unsigned_short(result, Address(str1, cnt1, scale));
+    load_unsigned_short(cnt2, Address(str2, cnt1, scale));
+    subl(result, cnt2);
+    jmp(POP_LABEL);
+
+    // Setup the registers to start vector comparison loop
+    bind(COMPARE_WIDE_VECTORS);
+    lea(str1, Address(str1, result, scale));
+    lea(str2, Address(str2, result, scale));
+    subl(result, stride2);
+    subl(cnt2, stride2);
+    jccb(Assembler::zero, COMPARE_WIDE_TAIL);
+    negptr(result);
+
+    //  In a loop, compare 16-chars (32-bytes) at once using (vpxor+vptest)
+    bind(COMPARE_WIDE_VECTORS_LOOP);
+    vmovdqu(vec1, Address(str1, result, scale));
+    vpxor(vec1, Address(str2, result, scale));
+    vptest(vec1, vec1);
+    jccb(Assembler::notZero, VECTOR_NOT_EQUAL);
+    addptr(result, stride2);
+    subl(cnt2, stride2);
+    jccb(Assembler::notZero, COMPARE_WIDE_VECTORS_LOOP);
+
+    // compare wide vectors tail
+    bind(COMPARE_WIDE_TAIL);
+    testptr(result, result);
+    jccb(Assembler::zero, LENGTH_DIFF_LABEL);
+
+    movl(result, stride2);
+    movl(cnt2, result);
+    negptr(result);
+    jmpb(COMPARE_WIDE_VECTORS_LOOP);
+
+    // Identifies the mismatching (higher or lower)16-bytes in the 32-byte vectors.
+    bind(VECTOR_NOT_EQUAL);
+    lea(str1, Address(str1, result, scale));
+    lea(str2, Address(str2, result, scale));
+    jmp(COMPARE_16_CHARS);
+
+    // Compare tail chars, length between 1 to 15 chars
+    bind(COMPARE_TAIL_LONG);
+    movl(cnt2, result);
+    cmpl(cnt2, stride);
+    jccb(Assembler::less, COMPARE_SMALL_STR);
+
+    movdqu(vec1, Address(str1, 0));
+    pcmpestri(vec1, Address(str2, 0), pcmpmask);
+    jcc(Assembler::below, COMPARE_INDEX_CHAR);
+    subptr(cnt2, stride);
+    jccb(Assembler::zero, LENGTH_DIFF_LABEL);
+    lea(str1, Address(str1, result, scale));
+    lea(str2, Address(str2, result, scale));
+    negptr(cnt2);
+    jmpb(WHILE_HEAD_LABEL);
+
+    bind(COMPARE_SMALL_STR);
+  } else if (UseSSE42Intrinsics) {
     Label COMPARE_WIDE_VECTORS, VECTOR_NOT_EQUAL, COMPARE_TAIL;
     int pcmpmask = 0x19;
-    // Setup to compare 16-byte vectors
+    // Setup to compare 8-char (16-byte) vectors,
+    // start from first character again because it has aligned address.
     movl(result, cnt2);
     andl(cnt2, ~(stride - 1));   // cnt2 holds the vector count
     jccb(Assembler::zero, COMPARE_TAIL);
@@ -5742,7 +5814,7 @@
     jccb(Assembler::notZero, COMPARE_WIDE_VECTORS);
 
     // compare wide vectors tail
-    testl(result, result);
+    testptr(result, result);
     jccb(Assembler::zero, LENGTH_DIFF_LABEL);
 
     movl(cnt2, stride);
@@ -5754,21 +5826,20 @@
 
     // Mismatched characters in the vectors
     bind(VECTOR_NOT_EQUAL);
-    addptr(result, cnt1);
-    movptr(cnt2, result);
-    load_unsigned_short(result, Address(str1, cnt2, scale));
-    load_unsigned_short(cnt1, Address(str2, cnt2, scale));
-    subl(result, cnt1);
+    addptr(cnt1, result);
+    load_unsigned_short(result, Address(str1, cnt1, scale));
+    load_unsigned_short(cnt2, Address(str2, cnt1, scale));
+    subl(result, cnt2);
     jmpb(POP_LABEL);
 
     bind(COMPARE_TAIL); // limit is zero
     movl(cnt2, result);
     // Fallthru to tail compare
   }
-
   // Shift str2 and str1 to the end of the arrays, negate min
-  lea(str1, Address(str1, cnt2, scale, 0));
-  lea(str2, Address(str2, cnt2, scale, 0));
+  lea(str1, Address(str1, cnt2, scale));
+  lea(str2, Address(str2, cnt2, scale));
+  decrementl(cnt2);  // first character was compared already
   negptr(cnt2);
 
   // Compare the rest of the elements
@@ -5833,7 +5904,44 @@
   shll(limit, 1);      // byte count != 0
   movl(result, limit); // copy
 
-  if (UseSSE42Intrinsics) {
+  if (UseAVX >= 2) {
+    // With AVX2, use 32-byte vector compare
+    Label COMPARE_WIDE_VECTORS, COMPARE_TAIL;
+
+    // Compare 32-byte vectors
+    andl(result, 0x0000001e);  //   tail count (in bytes)
+    andl(limit, 0xffffffe0);   // vector count (in bytes)
+    jccb(Assembler::zero, COMPARE_TAIL);
+
+    lea(ary1, Address(ary1, limit, Address::times_1));
+    lea(ary2, Address(ary2, limit, Address::times_1));
+    negptr(limit);
+
+    bind(COMPARE_WIDE_VECTORS);
+    vmovdqu(vec1, Address(ary1, limit, Address::times_1));
+    vmovdqu(vec2, Address(ary2, limit, Address::times_1));
+    vpxor(vec1, vec2);
+
+    vptest(vec1, vec1);
+    jccb(Assembler::notZero, FALSE_LABEL);
+    addptr(limit, 32);
+    jcc(Assembler::notZero, COMPARE_WIDE_VECTORS);
+
+    testl(result, result);
+    jccb(Assembler::zero, TRUE_LABEL);
+
+    vmovdqu(vec1, Address(ary1, result, Address::times_1, -32));
+    vmovdqu(vec2, Address(ary2, result, Address::times_1, -32));
+    vpxor(vec1, vec2);
+
+    vptest(vec1, vec1);
+    jccb(Assembler::notZero, FALSE_LABEL);
+    jmpb(TRUE_LABEL);
+
+    bind(COMPARE_TAIL); // limit is zero
+    movl(limit, result);
+    // Fallthru to tail compare
+  } else if (UseSSE42Intrinsics) {
     // With SSE4.2, use double quad vector compare
     Label COMPARE_WIDE_VECTORS, COMPARE_TAIL;