Move caller-saves saving/restoring to ReadBarrierMarkRegX.

Instead of saving/restoring live caller-save registers
before/after the call to read barrier mark entry points
ReadBarrierMarkRegX, have these entry points save/restore
all the caller-save registers themselves (except register
rX, which contains the return value).

Also refactor the assembly code of these entry points
using macros.

* Boot image code size variation on Nexus 5X
  (aosp_bullhead-userdebug build):
  - total ARM64 framework Oat files size change:
    119196792 bytes -> 115575920 bytes (-3.04%)
  - total ARM framework Oat files size change:
    100435212 bytes -> 97621188 bytes (-2.80%)

* Benchmarks (ARM64) score variations on Nexus 5X
  (aosp_bullhead-userdebug build):
  - RitzPerf (lower is better)
    - average score difference: -2.71%
  - CaffeineMark (higher is better)
    - no real difference for most tests
      (absolute variation lower than 1%)
    - better score on the "Method" benchmark:
      score variation 41253 -> 44891 (+8.82%)

Test: ART host and target (ARM, ARM64) tests.
Bug: 29506760
Bug: 12687968
Change-Id: I881bf73139a3f1c2bee9ffc6fc8c00f9a392afa6
diff --git a/runtime/arch/arm/entrypoints_init_arm.cc b/runtime/arch/arm/entrypoints_init_arm.cc
index 8f18ff3..dfa592c 100644
--- a/runtime/arch/arm/entrypoints_init_arm.cc
+++ b/runtime/arch/arm/entrypoints_init_arm.cc
@@ -33,7 +33,9 @@
 // Read barrier entrypoints.
 // art_quick_read_barrier_mark_regX uses an non-standard calling
 // convention: it expects its input in register X and returns its
-// result in that same register.
+// result in that same register, and saves and restores all
+// caller-save registers.
+extern "C" mirror::Object* art_quick_read_barrier_mark_reg00(mirror::Object*);
 extern "C" mirror::Object* art_quick_read_barrier_mark_reg01(mirror::Object*);
 extern "C" mirror::Object* art_quick_read_barrier_mark_reg02(mirror::Object*);
 extern "C" mirror::Object* art_quick_read_barrier_mark_reg03(mirror::Object*);
@@ -119,7 +121,7 @@
 
   // Read barrier.
   qpoints->pReadBarrierJni = ReadBarrierJni;
-  qpoints->pReadBarrierMarkReg00 = artReadBarrierMark;
+  qpoints->pReadBarrierMarkReg00 = art_quick_read_barrier_mark_reg00;
   qpoints->pReadBarrierMarkReg01 = art_quick_read_barrier_mark_reg01;
   qpoints->pReadBarrierMarkReg02 = art_quick_read_barrier_mark_reg02;
   qpoints->pReadBarrierMarkReg03 = art_quick_read_barrier_mark_reg03;