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7059037: Use BIS for zeroing on T4

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Use BIS for zeroing new allocated big (2Kb and more) objects and arrays.

Reviewed-by: never, twisti, ysr
This commit is contained in:
Vladimir Kozlov 2011-08-26 08:52:22 -07:00
parent 19f7fb98b8
commit 6446205688
14 changed files with 232 additions and 35 deletions
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62
hotspot/src/cpu/sparc/vm/assembler_sparc.cpp
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@ -4973,3 +4973,65 @@ void MacroAssembler::char_arrays_equals(Register ary1, Register ary2,
// Caller should set it:
// add(G0, 1, result); // equals
}
// Use BIS for zeroing (count is in bytes).
void MacroAssembler::bis_zeroing(Register to, Register count, Register temp, Label& Ldone) {
assert(UseBlockZeroing && VM_Version::has_block_zeroing(), "only works with BIS zeroing");
Register end = count;
int cache_line_size = VM_Version::prefetch_data_size();
// Minimum count when BIS zeroing can be used since
// it needs membar which is expensive.
int block_zero_size = MAX2(cache_line_size*3, (int)BlockZeroingLowLimit);
Label small_loop;
// Check if count is negative (dead code) or zero.
// Note, count uses 64bit in 64 bit VM.
cmp_and_brx_short(count, 0, Assembler::lessEqual, Assembler::pn, Ldone);
// Use BIS zeroing only for big arrays since it requires membar.
if (Assembler::is_simm13(block_zero_size)) { // < 4096
cmp(count, block_zero_size);
} else {
set(block_zero_size, temp);
cmp(count, temp);
}
br(Assembler::lessUnsigned, false, Assembler::pt, small_loop);
delayed()->add(to, count, end);
// Note: size is >= three (32 bytes) cache lines.
// Clean the beginning of space up to next cache line.
for (int offs = 0; offs < cache_line_size; offs += 8) {
stx(G0, to, offs);
}
// align to next cache line
add(to, cache_line_size, to);
and3(to, -cache_line_size, to);
// Note: size left >= two (32 bytes) cache lines.
// BIS should not be used to zero tail (64 bytes)
// to avoid zeroing a header of the following object.
sub(end, (cache_line_size*2)-8, end);
Label bis_loop;
bind(bis_loop);
stxa(G0, to, G0, Assembler::ASI_ST_BLKINIT_PRIMARY);
add(to, cache_line_size, to);
cmp_and_brx_short(to, end, Assembler::lessUnsigned, Assembler::pt, bis_loop);
// BIS needs membar.
membar(Assembler::StoreLoad);
add(end, (cache_line_size*2)-8, end); // restore end
cmp_and_brx_short(to, end, Assembler::greaterEqualUnsigned, Assembler::pn, Ldone);
// Clean the tail.
bind(small_loop);
stx(G0, to, 0);
add(to, 8, to);
cmp_and_brx_short(to, end, Assembler::lessUnsigned, Assembler::pt, small_loop);
nop(); // Separate short branches
}