Fix GC map generation edge case
Previously we checked the number of bits, but then rounded up to a
byte boundary. If ref_bitmap_bits was 65535, it would pass the check
but not actually fit in the 13 bits for ref_bitmap_bytes since we
rounded up to 8192 bytes.
Regression test infeasible due to smali limitations.
Bug: 21888453
Change-Id: If4b769431f27ecca14fe7852d017bcde01b3e146
diff --git a/compiler/dex/verified_method.cc b/compiler/dex/verified_method.cc
index ac7a4a7..9b141cc 100644
--- a/compiler/dex/verified_method.cc
+++ b/compiler/dex/verified_method.cc
@@ -89,14 +89,15 @@
DCHECK(dex_gc_map_.empty());
size_t num_entries, ref_bitmap_bits, pc_bits;
ComputeGcMapSizes(method_verifier, &num_entries, &ref_bitmap_bits, &pc_bits);
- // There's a single byte to encode the size of each bitmap.
- if (ref_bitmap_bits >= kBitsPerByte * 8192 /* 13-bit size */) {
+ const size_t ref_bitmap_bytes = RoundUp(ref_bitmap_bits, kBitsPerByte) / kBitsPerByte;
+ static constexpr size_t kFormatBits = 3;
+ // We have 16 - kFormatBits available for the ref_bitmap_bytes.
+ if ((ref_bitmap_bytes >> (16u - kFormatBits)) != 0) {
LOG(WARNING) << "Cannot encode GC map for method with " << ref_bitmap_bits << " registers: "
<< PrettyMethod(method_verifier->GetMethodReference().dex_method_index,
*method_verifier->GetMethodReference().dex_file);
return false;
}
- size_t ref_bitmap_bytes = RoundUp(ref_bitmap_bits, kBitsPerByte) / kBitsPerByte;
// There are 2 bytes to encode the number of entries.
if (num_entries >= 65536) {
LOG(WARNING) << "Cannot encode GC map for method with " << num_entries << " entries: "
@@ -122,7 +123,7 @@
size_t table_size = ((pc_bytes + ref_bitmap_bytes) * num_entries) + 4;
dex_gc_map_.reserve(table_size);
// Write table header.
- dex_gc_map_.push_back(format | ((ref_bitmap_bytes & ~0xFF) >> 5));
+ dex_gc_map_.push_back(format | ((ref_bitmap_bytes & ~0xFF) >> (kBitsPerByte - kFormatBits)));
dex_gc_map_.push_back(ref_bitmap_bytes & 0xFF);
dex_gc_map_.push_back(num_entries & 0xFF);
dex_gc_map_.push_back((num_entries >> 8) & 0xFF);
@@ -147,7 +148,7 @@
// Check that for every GC point there is a map entry, there aren't entries for non-GC points,
// that the table data is well formed and all references are marked (or not) in the bitmap.
verifier::DexPcToReferenceMap map(&data[0]);
- DCHECK_EQ(data.size(), map.RawSize());
+ CHECK_EQ(data.size(), map.RawSize()) << map.NumEntries() << " " << map.RegWidth();
size_t map_index = 0;
const DexFile::CodeItem* code_item = method_verifier->CodeItem();
for (size_t i = 0; i < code_item->insns_size_in_code_units_; i++) {
