diff options
Diffstat (limited to 'compiler/optimizing/code_generator_mips.cc')
| -rw-r--r-- | compiler/optimizing/code_generator_mips.cc | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/compiler/optimizing/code_generator_mips.cc b/compiler/optimizing/code_generator_mips.cc index 0ed5756b53..476e8ab944 100644 --- a/compiler/optimizing/code_generator_mips.cc +++ b/compiler/optimizing/code_generator_mips.cc @@ -1868,12 +1868,27 @@ void CodeGeneratorMIPS::MarkGCCard(Register object, if (value_can_be_null) { __ Beqz(value, &done); } + // Load the address of the card table into `card`. __ LoadFromOffset(kLoadWord, card, TR, Thread::CardTableOffset<kMipsPointerSize>().Int32Value()); + // Calculate the address of the card corresponding to `object`. __ Srl(temp, object, gc::accounting::CardTable::kCardShift); __ Addu(temp, card, temp); + // Write the `art::gc::accounting::CardTable::kCardDirty` value into the + // `object`'s card. + // + // Register `card` contains the address of the card table. Note that the card + // table's base is biased during its creation so that it always starts at an + // address whose least-significant byte is equal to `kCardDirty` (see + // art::gc::accounting::CardTable::Create). Therefore the SB instruction + // below writes the `kCardDirty` (byte) value into the `object`'s card + // (located at `card + object >> kCardShift`). + // + // This dual use of the value in register `card` (1. to calculate the location + // of the card to mark; and 2. to load the `kCardDirty` value) saves a load + // (no need to explicitly load `kCardDirty` as an immediate value). __ Sb(card, temp, 0); if (value_can_be_null) { __ Bind(&done); |