Refactor handling of conditional branches with known result.
Detect IF_cc and IF_ccZ instructions with known results in
the basic block optimization phase (instead for the codegen
phase) and replace them with GOTO/NOP. Kill blocks that are
unreachable as a result.
Change-Id: I169c2fa6f1e8af685f4f3a7fe622f5da862ce329
diff --git a/compiler/dex/mir_optimization.cc b/compiler/dex/mir_optimization.cc
index 1f630f7..55f2abc 100644
--- a/compiler/dex/mir_optimization.cc
+++ b/compiler/dex/mir_optimization.cc
@@ -399,6 +399,28 @@
return compiler_temp;
}
+static bool EvaluateBranch(Instruction::Code opcode, int32_t src1, int32_t src2) {
+ bool is_taken;
+ switch (opcode) {
+ case Instruction::IF_EQ: is_taken = (src1 == src2); break;
+ case Instruction::IF_NE: is_taken = (src1 != src2); break;
+ case Instruction::IF_LT: is_taken = (src1 < src2); break;
+ case Instruction::IF_GE: is_taken = (src1 >= src2); break;
+ case Instruction::IF_GT: is_taken = (src1 > src2); break;
+ case Instruction::IF_LE: is_taken = (src1 <= src2); break;
+ case Instruction::IF_EQZ: is_taken = (src1 == 0); break;
+ case Instruction::IF_NEZ: is_taken = (src1 != 0); break;
+ case Instruction::IF_LTZ: is_taken = (src1 < 0); break;
+ case Instruction::IF_GEZ: is_taken = (src1 >= 0); break;
+ case Instruction::IF_GTZ: is_taken = (src1 > 0); break;
+ case Instruction::IF_LEZ: is_taken = (src1 <= 0); break;
+ default:
+ LOG(FATAL) << "Unexpected opcode " << opcode;
+ UNREACHABLE();
+ }
+ return is_taken;
+}
+
/* Do some MIR-level extended basic block optimizations */
bool MIRGraph::BasicBlockOpt(BasicBlock* bb) {
if (bb->block_type == kDead) {
@@ -424,6 +446,46 @@
// Look for interesting opcodes, skip otherwise
Instruction::Code opcode = mir->dalvikInsn.opcode;
switch (opcode) {
+ case Instruction::IF_EQ:
+ case Instruction::IF_NE:
+ case Instruction::IF_LT:
+ case Instruction::IF_GE:
+ case Instruction::IF_GT:
+ case Instruction::IF_LE:
+ if (!IsConst(mir->ssa_rep->uses[1])) {
+ break;
+ }
+ FALLTHROUGH_INTENDED;
+ case Instruction::IF_EQZ:
+ case Instruction::IF_NEZ:
+ case Instruction::IF_LTZ:
+ case Instruction::IF_GEZ:
+ case Instruction::IF_GTZ:
+ case Instruction::IF_LEZ:
+ // Result known at compile time?
+ if (IsConst(mir->ssa_rep->uses[0])) {
+ int32_t rhs = (mir->ssa_rep->num_uses == 2) ? ConstantValue(mir->ssa_rep->uses[1]) : 0;
+ bool is_taken = EvaluateBranch(opcode, ConstantValue(mir->ssa_rep->uses[0]), rhs);
+ BasicBlockId edge_to_kill = is_taken ? bb->fall_through : bb->taken;
+ if (is_taken) {
+ // Replace with GOTO.
+ bb->fall_through = NullBasicBlockId;
+ mir->dalvikInsn.opcode = Instruction::GOTO;
+ mir->dalvikInsn.vA =
+ IsInstructionIfCc(opcode) ? mir->dalvikInsn.vC : mir->dalvikInsn.vB;
+ } else {
+ // Make NOP.
+ bb->taken = NullBasicBlockId;
+ mir->dalvikInsn.opcode = static_cast<Instruction::Code>(kMirOpNop);
+ }
+ mir->ssa_rep->num_uses = 0;
+ BasicBlock* successor_to_unlink = GetBasicBlock(edge_to_kill);
+ successor_to_unlink->ErasePredecessor(bb->id);
+ if (successor_to_unlink->predecessors.empty()) {
+ successor_to_unlink->KillUnreachable(this);
+ }
+ }
+ break;
case Instruction::CMPL_FLOAT:
case Instruction::CMPL_DOUBLE:
case Instruction::CMPG_FLOAT:
diff --git a/compiler/dex/quick/codegen_util.cc b/compiler/dex/quick/codegen_util.cc
index 1cde01e..58bcee2 100644
--- a/compiler/dex/quick/codegen_util.cc
+++ b/compiler/dex/quick/codegen_util.cc
@@ -922,28 +922,6 @@
NewLIR1(kPseudoDalvikByteCodeBoundary, WrapPointer(ArenaStrdup(inst_str)));
}
-bool Mir2Lir::EvaluateBranch(Instruction::Code opcode, int32_t src1, int32_t src2) {
- bool is_taken;
- switch (opcode) {
- case Instruction::IF_EQ: is_taken = (src1 == src2); break;
- case Instruction::IF_NE: is_taken = (src1 != src2); break;
- case Instruction::IF_LT: is_taken = (src1 < src2); break;
- case Instruction::IF_GE: is_taken = (src1 >= src2); break;
- case Instruction::IF_GT: is_taken = (src1 > src2); break;
- case Instruction::IF_LE: is_taken = (src1 <= src2); break;
- case Instruction::IF_EQZ: is_taken = (src1 == 0); break;
- case Instruction::IF_NEZ: is_taken = (src1 != 0); break;
- case Instruction::IF_LTZ: is_taken = (src1 < 0); break;
- case Instruction::IF_GEZ: is_taken = (src1 >= 0); break;
- case Instruction::IF_GTZ: is_taken = (src1 > 0); break;
- case Instruction::IF_LEZ: is_taken = (src1 <= 0); break;
- default:
- LOG(FATAL) << "Unexpected opcode " << opcode;
- UNREACHABLE();
- }
- return is_taken;
-}
-
// Convert relation of src1/src2 to src2/src1
ConditionCode Mir2Lir::FlipComparisonOrder(ConditionCode before) {
ConditionCode res;
diff --git a/compiler/dex/quick/mir_to_lir.cc b/compiler/dex/quick/mir_to_lir.cc
index 0d30927..68856cd 100644
--- a/compiler/dex/quick/mir_to_lir.cc
+++ b/compiler/dex/quick/mir_to_lir.cc
@@ -657,24 +657,12 @@
case Instruction::IF_GT:
case Instruction::IF_LE: {
LIR* taken = &label_list[bb->taken];
- // Result known at compile time?
- if (rl_src[0].is_const && rl_src[1].is_const) {
- bool is_taken = EvaluateBranch(opcode, mir_graph_->ConstantValue(rl_src[0].orig_sreg),
- mir_graph_->ConstantValue(rl_src[1].orig_sreg));
- BasicBlockId target_id = is_taken ? bb->taken : bb->fall_through;
- if (mir_graph_->IsBackedge(bb, target_id) &&
- (kLeafOptimization || !mir_graph_->HasSuspendTestBetween(bb, target_id))) {
- GenSuspendTest(opt_flags);
- }
- OpUnconditionalBranch(&label_list[target_id]);
- } else {
- if (mir_graph_->IsBackwardsBranch(bb) &&
- (kLeafOptimization || !mir_graph_->HasSuspendTestBetween(bb, bb->taken) ||
- !mir_graph_->HasSuspendTestBetween(bb, bb->fall_through))) {
- GenSuspendTest(opt_flags);
- }
- GenCompareAndBranch(opcode, rl_src[0], rl_src[1], taken);
+ if (mir_graph_->IsBackwardsBranch(bb) &&
+ (kLeafOptimization || !mir_graph_->HasSuspendTestBetween(bb, bb->taken) ||
+ !mir_graph_->HasSuspendTestBetween(bb, bb->fall_through))) {
+ GenSuspendTest(opt_flags);
}
+ GenCompareAndBranch(opcode, rl_src[0], rl_src[1], taken);
break;
}
case Instruction::IF_EQZ:
@@ -684,23 +672,12 @@
case Instruction::IF_GTZ:
case Instruction::IF_LEZ: {
LIR* taken = &label_list[bb->taken];
- // Result known at compile time?
- if (rl_src[0].is_const) {
- bool is_taken = EvaluateBranch(opcode, mir_graph_->ConstantValue(rl_src[0].orig_sreg), 0);
- BasicBlockId target_id = is_taken ? bb->taken : bb->fall_through;
- if (mir_graph_->IsBackedge(bb, target_id) &&
- (kLeafOptimization || !mir_graph_->HasSuspendTestBetween(bb, target_id))) {
- GenSuspendTest(opt_flags);
- }
- OpUnconditionalBranch(&label_list[target_id]);
- } else {
- if (mir_graph_->IsBackwardsBranch(bb) &&
- (kLeafOptimization || !mir_graph_->HasSuspendTestBetween(bb, bb->taken) ||
- !mir_graph_->HasSuspendTestBetween(bb, bb->fall_through))) {
- GenSuspendTest(opt_flags);
- }
- GenCompareZeroAndBranch(opcode, rl_src[0], taken);
+ if (mir_graph_->IsBackwardsBranch(bb) &&
+ (kLeafOptimization || !mir_graph_->HasSuspendTestBetween(bb, bb->taken) ||
+ !mir_graph_->HasSuspendTestBetween(bb, bb->fall_through))) {
+ GenSuspendTest(opt_flags);
}
+ GenCompareZeroAndBranch(opcode, rl_src[0], taken);
break;
}
diff --git a/compiler/dex/quick/mir_to_lir.h b/compiler/dex/quick/mir_to_lir.h
index 6847717..88b260c 100644
--- a/compiler/dex/quick/mir_to_lir.h
+++ b/compiler/dex/quick/mir_to_lir.h
@@ -666,7 +666,6 @@
void MarkBoundary(DexOffset offset, const char* inst_str);
void NopLIR(LIR* lir);
void UnlinkLIR(LIR* lir);
- bool EvaluateBranch(Instruction::Code opcode, int src1, int src2);
bool IsInexpensiveConstant(RegLocation rl_src);
ConditionCode FlipComparisonOrder(ConditionCode before);
ConditionCode NegateComparison(ConditionCode before);