Use mmapped boot image class table for PIC app HLoadClass.

Implement new HLoadClass load kind for boot image classes
referenced by PIC-compiled apps (i.e. prebuilts) that uses
PC-relative load from a boot image ClassTable mmapped into
the apps .bss. This reduces the size of the PIC prebuilts
that reference boot image classes compared to the kBssEntry
as we can completely avoid the slow path and stack map
unless we need to do the class initialization check.

Prebuilt services.odex for aosp_angler-userdebug (arm64):
  - before: 20312800
  - after: 19775352 (-525KiB)

Test: m test-art-host-gtest
Test: testrunner.py --host
Test: testrunner.py --host --pictest
Test: testrunner.py --target on Nexus 6P.
Test: testrunner.py --target --pictest on Nexus 6P.
Test: Nexus 6P boots.
Bug: 31951624
Change-Id: I13adb19a1fa7d095a72a41f09daa6101876e77a8

1 files changed, 6 insertions, 0 deletions

diff --git a/compiler/optimizing/nodes.h b/compiler/optimizing/nodes.h
index 5e8c77102a..b551f37135 100644
--- a/compiler/optimizing/nodes.h
+++ b/compiler/optimizing/nodes.h
@@ -5675,6 +5675,10 @@ class HLoadClass FINAL : public HInstruction {
     // Used for boot image classes referenced by apps in AOT- and JIT-compiled code.
     kBootImageAddress,
 
+    // Use a PC-relative load from a boot image ClassTable mmapped into the .bss
+    // of the oat file.
+    kBootImageClassTable,
+
     // Load from an entry in the .bss section using a PC-relative load.
     // Used for classes outside boot image when .bss is accessible with a PC-relative load.
     kBssEntry,
@@ -5820,6 +5824,7 @@ class HLoadClass FINAL : public HInstruction {
   static bool HasTypeReference(LoadKind load_kind) {
     return load_kind == LoadKind::kReferrersClass ||
         load_kind == LoadKind::kBootImageLinkTimePcRelative ||
+        load_kind == LoadKind::kBootImageClassTable ||
         load_kind == LoadKind::kBssEntry ||
         load_kind == LoadKind::kRuntimeCall;
   }
@@ -5853,6 +5858,7 @@ inline void HLoadClass::AddSpecialInput(HInstruction* special_input) {
   // including literal pool loads, which are PC-relative too.
   DCHECK(GetLoadKind() == LoadKind::kBootImageLinkTimePcRelative ||
          GetLoadKind() == LoadKind::kBootImageAddress ||
+         GetLoadKind() == LoadKind::kBootImageClassTable ||
          GetLoadKind() == LoadKind::kBssEntry) << GetLoadKind();
   DCHECK(special_input_.GetInstruction() == nullptr);
   special_input_ = HUserRecord<HInstruction*>(special_input);