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src/cpu/aarch64/vm/macroAssembler_aarch64.cpp
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@@ -4479,229 +4479,131 @@
bind(DONE);
BLOCK_COMMENT("} string_compare");
}
+// Compare Strings or char/byte arrays.
-void MacroAssembler::string_equals(Register str1, Register str2,
- Register cnt, Register result,
- Register tmp1) {
- Label SAME_CHARS, DONE, SHORT_LOOP, SHORT_STRING,
- NEXT_WORD;
+// is_string is true iff this is a string comparison.
- const Register tmp2 = rscratch1;
- assert_different_registers(str1, str2, cnt, result, tmp1, tmp2, rscratch2);
+// For Strings we're passed the address of the first characters in a1
+// and a2 and the length in cnt1.
- BLOCK_COMMENT("string_equals {");
+// For byte and char arrays we're passed the arrays themselves and we
+// have to extract length fields and do null checks here.
- // Start by assuming that the strings are not equal.
- mov(result, zr);
+// elem_size is the element size in bytes: either 1 or 2.
- // A very short string
- cmpw(cnt, 4);
- br(Assembler::LT, SHORT_STRING);
+// There are two implementations. For arrays >= 8 bytes, all
+// comparisons (including the final one, which may overlap) are
+// performed 8 bytes at a time. For arrays < 8 bytes, we compare a
+// halfword, then a short, and then a byte.
- // Check if the strings start at the same location.
- cmp(str1, str2);
- br(Assembler::EQ, SAME_CHARS);
-
- // Compare longwords
- {
- subw(cnt, cnt, 4); // The last longword is a special case
-
- // Move both string pointers to the last longword of their
- // strings, negate the remaining count, and convert it to bytes.
- lea(str1, Address(str1, cnt, Address::uxtw(1)));
- lea(str2, Address(str2, cnt, Address::uxtw(1)));
- sub(cnt, zr, cnt, LSL, 1);
-
- // Loop, loading longwords and comparing them into rscratch2.
- bind(NEXT_WORD);
- ldr(tmp1, Address(str1, cnt));
- ldr(tmp2, Address(str2, cnt));
- adds(cnt, cnt, wordSize);
- eor(rscratch2, tmp1, tmp2);
- cbnz(rscratch2, DONE);
- br(Assembler::LT, NEXT_WORD);
-
- // Last longword. In the case where length == 4 we compare the
- // same longword twice, but that's still faster than another
- // conditional branch.
-
- ldr(tmp1, Address(str1));
- ldr(tmp2, Address(str2));
- eor(rscratch2, tmp1, tmp2);
- cbz(rscratch2, SAME_CHARS);
- b(DONE);
- }
-
- bind(SHORT_STRING);
- // Is the length zero?
- cbz(cnt, SAME_CHARS);
-
- bind(SHORT_LOOP);
- load_unsigned_short(tmp1, Address(post(str1, 2)));
- load_unsigned_short(tmp2, Address(post(str2, 2)));
- subw(tmp1, tmp1, tmp2);
- cbnz(tmp1, DONE);
- sub(cnt, cnt, 1);
- cbnz(cnt, SHORT_LOOP);
-
- // Strings are equal.
- bind(SAME_CHARS);
- mov(result, true);
-
- // That's it
- bind(DONE);
-
- BLOCK_COMMENT("} string_equals");
-}
-
-
-void MacroAssembler::byte_arrays_equals(Register ary1, Register ary2,
- Register result, Register tmp1)
+void MacroAssembler::arrays_equals(Register a1, Register a2,
+ Register result, Register cnt1,
+ int elem_size, bool is_string)
{
- Register cnt1 = rscratch1;
- Register cnt2 = rscratch2;
+ Label SAME, DONE, SHORT, NEXT_WORD;
+ Register tmp1 = rscratch1;
Register tmp2 = rscratch2;
-
- Label SAME, DIFFER, NEXT, TAIL07, TAIL03, TAIL01;
-
+ Register cnt2 = tmp2; // cnt2 only used in array length compare
+ int elem_per_word = wordSize/elem_size;
+ int log_elem_size = exact_log2(elem_size);
int length_offset = arrayOopDesc::length_offset_in_bytes();
- int base_offset = arrayOopDesc::base_offset_in_bytes(T_BYTE);
-
- BLOCK_COMMENT("byte_arrays_equals {");
-
- // different until proven equal
- mov(result, false);
-
- // same array?
- cmp(ary1, ary2);
- br(Assembler::EQ, SAME);
-
- // ne if either null
- cbz(ary1, DIFFER);
- cbz(ary2, DIFFER);
-
- // lengths ne?
- ldrw(cnt1, Address(ary1, length_offset));
- ldrw(cnt2, Address(ary2, length_offset));
- cmp(cnt1, cnt2);
- br(Assembler::NE, DIFFER);
-
- lea(ary1, Address(ary1, base_offset));
- lea(ary2, Address(ary2, base_offset));
-
- subs(cnt1, cnt1, 8);
- br(LT, TAIL07);
-
- BIND(NEXT);
- ldr(tmp1, Address(post(ary1, 8)));
- ldr(tmp2, Address(post(ary2, 8)));
- subs(cnt1, cnt1, 8);
- eor(tmp1, tmp1, tmp2);
- cbnz(tmp1, DIFFER);
- br(GE, NEXT);
+ int base_offset
+ = arrayOopDesc::base_offset_in_bytes(elem_size == 2 ? T_CHAR : T_BYTE);
- BIND(TAIL07); // 0-7 bytes left, cnt1 = #bytes left - 4
- tst(cnt1, 0b100);
- br(EQ, TAIL03);
- ldrw(tmp1, Address(post(ary1, 4)));
- ldrw(tmp2, Address(post(ary2, 4)));
- cmp(tmp1, tmp2);
- br(NE, DIFFER);
-
- BIND(TAIL03); // 0-3 bytes left, cnt1 = #bytes left - 4
- tst(cnt1, 0b10);
- br(EQ, TAIL01);
- ldrh(tmp1, Address(post(ary1, 2)));
- ldrh(tmp2, Address(post(ary2, 2)));
- cmp(tmp1, tmp2);
- br(NE, DIFFER);
- BIND(TAIL01); // 0-1 byte left
- tst(cnt1, 0b01);
- br(EQ, SAME);
- ldrb(tmp1, ary1);
- ldrb(tmp2, ary2);
- cmp(tmp1, tmp2);
- br(NE, DIFFER);
+ assert(elem_size == 1 || elem_size == 2, "must be char or byte");
+ assert_different_registers(a1, a2, result, cnt1, rscratch1, rscratch2);
- BIND(SAME);
- mov(result, true);
- BIND(DIFFER); // result already set
-
- BLOCK_COMMENT("} byte_arrays_equals");
-}
-
-// Compare char[] arrays aligned to 4 bytes
-void MacroAssembler::char_arrays_equals(Register ary1, Register ary2,
- Register result, Register tmp1)
-{
- Register cnt1 = rscratch1;
- Register cnt2 = rscratch2;
- Register tmp2 = rscratch2;
-
- Label SAME, DIFFER, NEXT, TAIL03, TAIL01;
+ BLOCK_COMMENT(is_string ? "string_equals {" : "array_equals {");
- int length_offset = arrayOopDesc::length_offset_in_bytes();
- int base_offset = arrayOopDesc::base_offset_in_bytes(T_CHAR);
+ mov(result, false);
- BLOCK_COMMENT("char_arrays_equals {");
+ if (! is_string) {
+ // if (a==a2)
+ // return true;
+ eor(rscratch1, a1, a2);
+ cbz(rscratch1, SAME);
+ // if (a==null || a2==null)
+ // return false;
+ cbz(a1, DONE);
+ cbz(a2, DONE);
+ // if (a1.length != a2.length)
+ // return false;
+ ldrw(cnt1, Address(a1, length_offset));
+ ldrw(cnt2, Address(a2, length_offset));
+ eorw(rscratch1, cnt1, cnt2);
+ cbnzw(rscratch1, DONE);
- // different until proven equal
- mov(result, false);
+ lea(a1, Address(a1, base_offset));
+ lea(a2, Address(a2, base_offset));
+ }
- // same array?
- cmp(ary1, ary2);
- br(Assembler::EQ, SAME);
-
- // ne if either null
- cbz(ary1, DIFFER);
- cbz(ary2, DIFFER);
-
- // lengths ne?
- ldrw(cnt1, Address(ary1, length_offset));
- ldrw(cnt2, Address(ary2, length_offset));
- cmp(cnt1, cnt2);
- br(Assembler::NE, DIFFER);
-
- lea(ary1, Address(ary1, base_offset));
- lea(ary2, Address(ary2, base_offset));
-
- subs(cnt1, cnt1, 4);
- br(LT, TAIL03);
-
- BIND(NEXT);
- ldr(tmp1, Address(post(ary1, 8)));
- ldr(tmp2, Address(post(ary2, 8)));
- subs(cnt1, cnt1, 4);
+ // Check for short strings, i.e. smaller than wordSize.
+ subs(cnt1, cnt1, elem_per_word);
+ br(Assembler::LT, SHORT);
+
+ // Main 8 byte comparison loop.
+ bind(NEXT_WORD); {
+ ldr(tmp1, Address(post(a1, wordSize)));
+ ldr(tmp2, Address(post(a2, wordSize)));
+ subs(cnt1, cnt1, elem_per_word);
+ eor(tmp1, tmp1, tmp2);
+ cbnz(tmp1, DONE);
+ } br(GT, NEXT_WORD);
+ // Last longword. In the case where length == 4 we compare the
+ // same longword twice, but that's still faster than another
+ // conditional branch.
+ // cnt1 could be 0, -1, -2, -3, -4 for chars; -4 only happens when
+ // length == 4.
+ if (log_elem_size > 0)
+ lsl(cnt1, cnt1, log_elem_size);
+ ldr(tmp1, Address(a1, cnt1));
+ ldr(tmp2, Address(a2, cnt1));
eor(tmp1, tmp1, tmp2);
- cbnz(tmp1, DIFFER);
- br(GE, NEXT);
+ cbnz(tmp1, DONE);
+ b(SAME);
- BIND(TAIL03); // 0-3 chars left, cnt1 = #chars left - 4
- tst(cnt1, 0b10);
- br(EQ, TAIL01);
- ldrw(tmp1, Address(post(ary1, 4)));
- ldrw(tmp2, Address(post(ary2, 4)));
- cmp(tmp1, tmp2);
- br(NE, DIFFER);
- BIND(TAIL01); // 0-1 chars left
- tst(cnt1, 0b01);
- br(EQ, SAME);
- ldrh(tmp1, ary1);
- ldrh(tmp2, ary2);
- cmp(tmp1, tmp2);
- br(NE, DIFFER);
+ bind(SHORT);
+ Label TAIL03, TAIL01;
- BIND(SAME);
+ tbz(cnt1, 2 - log_elem_size, TAIL03); // 0-7 bytes left.
+ {
+ ldrw(tmp1, Address(post(a1, 4)));
+ ldrw(tmp2, Address(post(a2, 4)));
+ eorw(tmp1, tmp1, tmp2);
+ cbnzw(tmp1, DONE);
+ }
+ bind(TAIL03);
+ tbz(cnt1, 1 - log_elem_size, TAIL01); // 0-3 bytes left.
+ {
+ ldrh(tmp1, Address(post(a1, 2)));
+ ldrh(tmp2, Address(post(a2, 2)));
+ eorw(tmp1, tmp1, tmp2);
+ cbnzw(tmp1, DONE);
+ }
+ bind(TAIL01);
+ if (elem_size == 1) { // Only needed when comparing byte arrays.
+ tbz(cnt1, 0, SAME); // 0-1 bytes left.
+ {
+ ldrb(tmp1, a1);
+ ldrb(tmp2, a2);
+ eorw(tmp1, tmp1, tmp2);
+ cbnzw(tmp1, DONE);
+ }
+ }
+ // Arrays are equal.
+ bind(SAME);
mov(result, true);
- BIND(DIFFER); // result already set
- BLOCK_COMMENT("} char_arrays_equals");
+ // That's it.
+ bind(DONE);
+ BLOCK_COMMENT(is_string ? "} string_equals" : "} array_equals");
}
+
// encode char[] to byte[] in ISO_8859_1
void MacroAssembler::encode_iso_array(Register src, Register dst,
Register len, Register result,
FloatRegister Vtmp1, FloatRegister Vtmp2,
FloatRegister Vtmp3, FloatRegister Vtmp4)
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