Optimize stack map decoding.

We usually read several consecutive varints.
Add helper method optimized for that use case
(ideally reading 8 varints from single load).

This improves app startup by 0.4% (maps,speed).
PMD on golem seems to get around 5% faster.
CodeInfo::Decode on its own is 25% faster.

Bug: 133257467
Test: ./art/test.py -b --host --64
Change-Id: Iaf7e8469ed6397b1d1d4102e409b5731f7229557

1 files changed, 9 insertions, 0 deletions

diff --git a/compiler/optimizing/stack_map_stream.cc b/compiler/optimizing/stack_map_stream.cc
index 60ca61c133..8c3664312d 100644
--- a/compiler/optimizing/stack_map_stream.cc
+++ b/compiler/optimizing/stack_map_stream.cc
@@ -52,6 +52,15 @@ void StackMapStream::BeginMethod(size_t frame_size_in_bytes,
   core_spill_mask_ = core_spill_mask;
   fp_spill_mask_ = fp_spill_mask;
   num_dex_registers_ = num_dex_registers;
+
+  if (kVerifyStackMaps) {
+    dchecks_.emplace_back([=](const CodeInfo& code_info) {
+      DCHECK_EQ(code_info.packed_frame_size_, frame_size_in_bytes / kStackAlignment);
+      DCHECK_EQ(code_info.core_spill_mask_, core_spill_mask);
+      DCHECK_EQ(code_info.fp_spill_mask_, fp_spill_mask);
+      DCHECK_EQ(code_info.number_of_dex_registers_, num_dex_registers);
+    });
+  }
 }
 
 void StackMapStream::EndMethod() {