Remove custom CheckCast slow path caller saves for Baker CC.

For Baker CC, CheckCast has both a read-barrier marking slow
path and a pCheckCast slow path. When the latter is known to
leave the method, i.e. known to throw outside a try-block,
we do not need to save live registers for retrieval for the
exception delivery and since the read-barrier marking does
not need to save any registers either we were setting the
custom slow path caller saves to empty to avoid reserving
unnecessary spill space. Hovewer, this also leads to marking
live references in caller-save registers in the register
mask and while the read-barrier marking entrypoint doesn't
care, it causes a stack walk for the pCheckCast to try and
retrieve an unsaved register.

For the time being, revert to the default caller saves.

This is a partial revert of
    https://android-review.googlesource.com/254920

Test: Run ART test suite on host and Nexus 9.
Bug: 29231980
Bug: 30212852
Change-Id: I4e22125f3d8903c97506aa2e6e66bea8e8e6baef

1 files changed, 0 insertions, 5 deletions

diff --git a/compiler/optimizing/code_generator_arm.cc b/compiler/optimizing/code_generator_arm.cc
index 4c41ac89e7..40c2b9c1ec 100644
--- a/compiler/optimizing/code_generator_arm.cc
+++ b/compiler/optimizing/code_generator_arm.cc
@@ -5738,7 +5738,6 @@ void LocationsBuilderARM::VisitCheckCast(HCheckCast* instruction) {
   bool throws_into_catch = instruction->CanThrowIntoCatchBlock();
 
   TypeCheckKind type_check_kind = instruction->GetTypeCheckKind();
-  bool baker_read_barrier_slow_path = false;
   switch (type_check_kind) {
     case TypeCheckKind::kExactCheck:
     case TypeCheckKind::kAbstractClassCheck:
@@ -5747,7 +5746,6 @@ void LocationsBuilderARM::VisitCheckCast(HCheckCast* instruction) {
       call_kind = (throws_into_catch || kEmitCompilerReadBarrier) ?
           LocationSummary::kCallOnSlowPath :
           LocationSummary::kNoCall;  // In fact, call on a fatal (non-returning) slow path.
-      baker_read_barrier_slow_path = kUseBakerReadBarrier && !throws_into_catch;
       break;
     case TypeCheckKind::kArrayCheck:
     case TypeCheckKind::kUnresolvedCheck:
@@ -5757,9 +5755,6 @@ void LocationsBuilderARM::VisitCheckCast(HCheckCast* instruction) {
   }
 
   LocationSummary* locations = new (GetGraph()->GetArena()) LocationSummary(instruction, call_kind);
-  if (baker_read_barrier_slow_path) {
-    locations->SetCustomSlowPathCallerSaves(RegisterSet());  // No caller-save registers.
-  }
   locations->SetInAt(0, Location::RequiresRegister());
   locations->SetInAt(1, Location::RequiresRegister());
   // Note that TypeCheckSlowPathARM uses this "temp" register too.