Quick: Eliminate check-cast guaranteed by instance-of.
Eliminate check-cast if the result of an instance-of with
the very same type on the same value is used to branch to
the check-cast's block or a dominator of it.
Note that there already exists a verifier-based elimination
of check-cast but it excludes check-cast on interfaces. This
new optimization works for interface types and, since it's
GVN-based, it can better recognize when the same reference
is used for instance-of and check-cast.
Change-Id: Ib315199805099d1cb0534bb4a90dc51baa409685
diff --git a/compiler/dex/quick/gen_common.cc b/compiler/dex/quick/gen_common.cc
index e57889a..32a469d 100644
--- a/compiler/dex/quick/gen_common.cc
+++ b/compiler/dex/quick/gen_common.cc
@@ -1403,7 +1403,12 @@
}
}
-void Mir2Lir::GenCheckCast(uint32_t insn_idx, uint32_t type_idx, RegLocation rl_src) {
+void Mir2Lir::GenCheckCast(int opt_flags, uint32_t insn_idx, uint32_t type_idx,
+ RegLocation rl_src) {
+ if ((opt_flags & MIR_IGNORE_CHECK_CAST) != 0) {
+ // Compiler analysis proved that this check-cast would never cause an exception.
+ return;
+ }
bool type_known_final, type_known_abstract, use_declaring_class;
bool needs_access_check = !cu_->compiler_driver->CanAccessTypeWithoutChecks(cu_->method_idx,
*cu_->dex_file,
diff --git a/compiler/dex/quick/mir_to_lir.cc b/compiler/dex/quick/mir_to_lir.cc
index 8348626..8edc5fc 100644
--- a/compiler/dex/quick/mir_to_lir.cc
+++ b/compiler/dex/quick/mir_to_lir.cc
@@ -632,7 +632,7 @@
break;
case Instruction::CHECK_CAST: {
- GenCheckCast(mir->offset, vB, rl_src[0]);
+ GenCheckCast(opt_flags, mir->offset, vB, rl_src[0]);
break;
}
case Instruction::INSTANCE_OF:
diff --git a/compiler/dex/quick/mir_to_lir.h b/compiler/dex/quick/mir_to_lir.h
index 6f3f057..9a56171 100644
--- a/compiler/dex/quick/mir_to_lir.h
+++ b/compiler/dex/quick/mir_to_lir.h
@@ -826,7 +826,7 @@
void GenNewInstance(uint32_t type_idx, RegLocation rl_dest);
void GenThrow(RegLocation rl_src);
void GenInstanceof(uint32_t type_idx, RegLocation rl_dest, RegLocation rl_src);
- void GenCheckCast(uint32_t insn_idx, uint32_t type_idx, RegLocation rl_src);
+ void GenCheckCast(int opt_flags, uint32_t insn_idx, uint32_t type_idx, RegLocation rl_src);
void GenLong3Addr(OpKind first_op, OpKind second_op, RegLocation rl_dest,
RegLocation rl_src1, RegLocation rl_src2);
virtual void GenShiftOpLong(Instruction::Code opcode, RegLocation rl_dest,