VM-codegen: Clean up the way we emit code for comparison instructions.

runtime/vm/intermediate_language_arm64.cc

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_ARM64.
 #if defined(TARGET_ARCH_ARM64)
 
 #include "vm/intermediate_language.h"
 
 #include "vm/compiler.h"
@@ skipping 147 matching lines @@
 
 
 void IfThenElseInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   const Register result = locs()->out(0).reg();
 
   Location left = locs()->in(0);
   Location right = locs()->in(1);
   ASSERT(!left.IsConstant() || !right.IsConstant());
 
   // Emit comparison code. This must not overwrite the result register.
+  // IfThenElseInstr::Supports() should prevent EmitComparisonCode from using
+  // the labels or returning an invalid condition.
   BranchLabels labels = {NULL, NULL, NULL};
   Condition true_condition = comparison()->EmitComparisonCode(compiler, labels);
+  ASSERT(true_condition != kInvalidCondition);
 
   const bool is_power_of_two_kind = IsPowerOfTwoKind(if_true_, if_false_);
 
   intptr_t true_value = if_true_;
   intptr_t false_value = if_false_;
 
   if (is_power_of_two_kind) {
     if (true_value == 0) {
       // We need to have zero in result on true_condition.
       true_condition = NegateCondition(true_condition);
@@ skipping 353 matching lines @@
       return GE;
     default:
       UNREACHABLE();
       return VS;
   }
 }
 
 
 static Condition EmitDoubleComparisonOp(FlowGraphCompiler* compiler,
                                         LocationSummary* locs,
+                                        BranchLabels labels,
                                         Token::Kind kind) {
   const VRegister left = locs->in(0).fpu_reg();
   const VRegister right = locs->in(1).fpu_reg();
   __ fcmpd(left, right);
   Condition true_condition = TokenKindToDoubleCondition(kind);
+  if (true_condition != NE) {
+    // Special case for NaN comparison. Result is always false unless
+    // relational operator is !=.
+    __ b(labels.false_label, VS);
+  }
   return true_condition;
 }
 
 
 Condition EqualityCompareInstr::EmitComparisonCode(FlowGraphCompiler* compiler,
                                                    BranchLabels labels) {
   if (operation_cid() == kSmiCid) {
     return EmitSmiComparisonOp(compiler, locs(), kind());
   } else {
     ASSERT(operation_cid() == kDoubleCid);
-    return EmitDoubleComparisonOp(compiler, locs(), kind());
+    return EmitDoubleComparisonOp(compiler, locs(), labels, kind());
   }
 }
 
 
-void EqualityCompareInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
-  ASSERT((kind() == Token::kEQ) || (kind() == Token::kNE));
-  Label is_true, is_false;
-  BranchLabels labels = {&is_true, &is_false, &is_false};
-  Condition true_condition = EmitComparisonCode(compiler, labels);
-  if ((operation_cid() == kDoubleCid) && (true_condition != NE)) {
-    // Special case for NaN comparison. Result is always false unless
-    // relational operator is !=.
-    __ b(&is_false, VS);
-  }
-  EmitBranchOnCondition(compiler, true_condition, labels);
-  // TODO(zra): instead of branching, use the csel instruction to get
-  // True or False into result.
-  const Register result = locs()->out(0).reg();
-  Label done;
-  __ Bind(&is_false);
-  __ LoadObject(result, Bool::False());
-  __ b(&done);
-  __ Bind(&is_true);
-  __ LoadObject(result, Bool::True());
-  __ Bind(&done);
-}
-
-
-void EqualityCompareInstr::EmitBranchCode(FlowGraphCompiler* compiler,
-                                          BranchInstr* branch) {
-  ASSERT((kind() == Token::kNE) || (kind() == Token::kEQ));
-
-  BranchLabels labels = compiler->CreateBranchLabels(branch);
-  Condition true_condition = EmitComparisonCode(compiler, labels);
-  if ((operation_cid() == kDoubleCid) && (true_condition != NE)) {
-    // Special case for NaN comparison. Result is always false unless
-    // relational operator is !=.
-    __ b(labels.false_label, VS);
-  }
-  EmitBranchOnCondition(compiler, true_condition, labels);
-}
-
-
 LocationSummary* TestSmiInstr::MakeLocationSummary(Zone* zone, bool opt) const {
   const intptr_t kNumInputs = 2;
   const intptr_t kNumTemps = 0;
   LocationSummary* locs = new (zone)
       LocationSummary(zone, kNumInputs, kNumTemps, LocationSummary::kNoCall);
   locs->set_in(0, Location::RequiresRegister());
   // Only one input can be a constant operand. The case of two constant
   // operands should be handled by constant propagation.
   locs->set_in(1, Location::RegisterOrConstant(right()));
   return locs;
 }
 
 
 Condition TestSmiInstr::EmitComparisonCode(FlowGraphCompiler* compiler,
                                            BranchLabels labels) {
   const Register left = locs()->in(0).reg();
   Location right = locs()->in(1);
   if (right.IsConstant()) {
     ASSERT(right.constant().IsSmi());
     const int64_t imm = reinterpret_cast<int64_t>(right.constant().raw());
     __ TestImmediate(left, imm);
   } else {
     __ tst(left, Operand(right.reg()));
   }
   Condition true_condition = (kind() == Token::kNE) ? NE : EQ;
   return true_condition;
 }
 
 
-void TestSmiInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
-  // Never emitted outside of the BranchInstr.
-  UNREACHABLE();
-}
-
-
-void TestSmiInstr::EmitBranchCode(FlowGraphCompiler* compiler,
-                                  BranchInstr* branch) {
-  BranchLabels labels = compiler->CreateBranchLabels(branch);
-  Condition true_condition = EmitComparisonCode(compiler, labels);
-  EmitBranchOnCondition(compiler, true_condition, labels);
-}
-
-
 LocationSummary* TestCidsInstr::MakeLocationSummary(Zone* zone,
                                                     bool opt) const {
   const intptr_t kNumInputs = 1;
   const intptr_t kNumTemps = 1;
   LocationSummary* locs = new (zone)
       LocationSummary(zone, kNumInputs, kNumTemps, LocationSummary::kNoCall);
   locs->set_in(0, Location::RequiresRegister());
   locs->set_temp(0, Location::RequiresRegister());
   locs->set_out(0, Location::RequiresRegister());
   return locs;
@@ skipping 32 matching lines @@
     // If the cid is not in the list, jump to the opposite label from the cids
     // that are in the list.  These must be all the same (see asserts in the
     // constructor).
     Label* target = result ? labels.false_label : labels.true_label;
     if (target != labels.fall_through) {
       __ b(target);
     }
   } else {
     __ b(deopt);
   }
-  // Dummy result as the last instruction is a jump, any conditional
-  // branch using the result will therefore be skipped.
-  return EQ;
+  // Dummy result as this method already did the jump, there's no need
+  // for the caller to branch on a condition.
+  return kInvalidCondition;
 }
 
 
-void TestCidsInstr::EmitBranchCode(FlowGraphCompiler* compiler,
-                                   BranchInstr* branch) {
-  BranchLabels labels = compiler->CreateBranchLabels(branch);
-  EmitComparisonCode(compiler, labels);
-}
-
-
-void TestCidsInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
-  const Register result_reg = locs()->out(0).reg();
-  Label is_true, is_false, done;
-  BranchLabels labels = {&is_true, &is_false, &is_false};
-  EmitComparisonCode(compiler, labels);
-  // TODO(zra): instead of branching, use the csel instruction to get
-  // True or False into result.
-  __ Bind(&is_false);
-  __ LoadObject(result_reg, Bool::False());
-  __ b(&done);
-  __ Bind(&is_true);
-  __ LoadObject(result_reg, Bool::True());
-  __ Bind(&done);
-}
-
-
 LocationSummary* RelationalOpInstr::MakeLocationSummary(Zone* zone,
                                                         bool opt) const {
   const intptr_t kNumInputs = 2;
   const intptr_t kNumTemps = 0;
   if (operation_cid() == kDoubleCid) {
     LocationSummary* summary = new (zone)
         LocationSummary(zone, kNumInputs, kNumTemps, LocationSummary::kNoCall);
     summary->set_in(0, Location::RequiresFpuRegister());
     summary->set_in(1, Location::RequiresFpuRegister());
     summary->set_out(0, Location::RequiresRegister());
@@ skipping 12 matching lines @@
   return summary;
 }
 
 
 Condition RelationalOpInstr::EmitComparisonCode(FlowGraphCompiler* compiler,
                                                 BranchLabels labels) {
   if (operation_cid() == kSmiCid) {
     return EmitSmiComparisonOp(compiler, locs(), kind());
   } else {
     ASSERT(operation_cid() == kDoubleCid);
-    return EmitDoubleComparisonOp(compiler, locs(), kind());
+    return EmitDoubleComparisonOp(compiler, locs(), labels, kind());
   }
 }
 
 
-void RelationalOpInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
-  Label is_true, is_false;
-  BranchLabels labels = {&is_true, &is_false, &is_false};
-  Condition true_condition = EmitComparisonCode(compiler, labels);
-  if ((operation_cid() == kDoubleCid) && (true_condition != NE)) {
-    // Special case for NaN comparison. Result is always false unless
-    // relational operator is !=.
-    __ b(&is_false, VS);
-  }
-  EmitBranchOnCondition(compiler, true_condition, labels);
-  // TODO(zra): instead of branching, use the csel instruction to get
-  // True or False into result.
-  const Register result = locs()->out(0).reg();
-  Label done;
-  __ Bind(&is_false);
-  __ LoadObject(result, Bool::False());
-  __ b(&done);
-  __ Bind(&is_true);
-  __ LoadObject(result, Bool::True());
-  __ Bind(&done);
-}
-
-
-void RelationalOpInstr::EmitBranchCode(FlowGraphCompiler* compiler,
-                                       BranchInstr* branch) {
-  BranchLabels labels = compiler->CreateBranchLabels(branch);
-  Condition true_condition = EmitComparisonCode(compiler, labels);
-  if ((operation_cid() == kDoubleCid) && (true_condition != NE)) {
-    // Special case for NaN comparison. Result is always false unless
-    // relational operator is !=.
-    __ b(labels.false_label, VS);
-  }
-  EmitBranchOnCondition(compiler, true_condition, labels);
-}
-
-
 LocationSummary* NativeCallInstr::MakeLocationSummary(Zone* zone,
                                                       bool opt) const {
   return MakeCallSummary(zone);
 }
 
 
 void NativeCallInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   SetupNative();
   const Register result = locs()->out(0).reg();
 
@@ skipping 2301 matching lines @@
 
 void CheckedSmiComparisonInstr::EmitBranchCode(FlowGraphCompiler* compiler,
                                                BranchInstr* branch) {
   BranchLabels labels = compiler->CreateBranchLabels(branch);
   CheckedSmiComparisonSlowPath* slow_path = new CheckedSmiComparisonSlowPath(
       this, compiler->CurrentTryIndex(), labels,
       /* merged = */ true);
   compiler->AddSlowPathCode(slow_path);
   EMIT_SMI_CHECK;
   Condition true_condition = EmitComparisonCode(compiler, labels);
+  ASSERT(true_condition != kInvalidCondition);
   EmitBranchOnCondition(compiler, true_condition, labels);
   __ Bind(slow_path->exit_label());
 }
 
 
 void CheckedSmiComparisonInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   Label true_label, false_label, done;
   BranchLabels labels = {&true_label, &false_label, &false_label};
   CheckedSmiComparisonSlowPath* slow_path = new CheckedSmiComparisonSlowPath(
       this, compiler->CurrentTryIndex(), labels,
       /* merged = */ false);
   compiler->AddSlowPathCode(slow_path);
   EMIT_SMI_CHECK;
   Condition true_condition = EmitComparisonCode(compiler, labels);
+  ASSERT(true_condition != kInvalidCondition);
   EmitBranchOnCondition(compiler, true_condition, labels);
   Register result = locs()->out(0).reg();
   __ Bind(&false_label);
   __ LoadObject(result, Bool::False());
   __ b(&done);
   __ Bind(&true_label);
   __ LoadObject(result, Bool::True());
   __ Bind(&done);
   __ Bind(slow_path->exit_label());
 }
@@ skipping 608 matching lines @@
     __ vmovrd(temp, value, 0);
     // Mask off the sign.
     __ AndImmediate(temp, temp, 0x7FFFFFFFFFFFFFFFLL);
     // Compare with +infinity.
     __ CompareImmediate(temp, 0x7FF0000000000000LL);
     return is_negated ? NE : EQ;
   }
 }
 
 
-void DoubleTestOpInstr::EmitBranchCode(FlowGraphCompiler* compiler,
-                                       BranchInstr* branch) {
-  ASSERT(compiler->is_optimizing());
-  BranchLabels labels = compiler->CreateBranchLabels(branch);
-  Condition true_condition = EmitComparisonCode(compiler, labels);
-  EmitBranchOnCondition(compiler, true_condition, labels);
-}
-
-
-void DoubleTestOpInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
-  ASSERT(compiler->is_optimizing());
-  Label is_true, is_false;
-  BranchLabels labels = {&is_true, &is_false, &is_false};
-  Condition true_condition = EmitComparisonCode(compiler, labels);
-  const Register result = locs()->out(0).reg();
-  if (op_kind() == MethodRecognizer::kDouble_getIsNaN) {
-    __ LoadObject(result, Bool::False());
-    __ LoadObject(TMP, Bool::True());
-    __ csel(result, TMP, result, true_condition);
-  } else {
-    __ LoadObject(result, Bool::False());
-    __ LoadObject(TMP, Bool::True());
-    __ csel(result, TMP, result, true_condition);
-  }
-}
-
-
 LocationSummary* BinaryFloat32x4OpInstr::MakeLocationSummary(Zone* zone,
                                                              bool opt) const {
   const intptr_t kNumInputs = 2;
   const intptr_t kNumTemps = 0;
   LocationSummary* summary = new (zone)
       LocationSummary(zone, kNumInputs, kNumTemps, LocationSummary::kNoCall);
   summary->set_in(0, Location::RequiresFpuRegister());
   summary->set_in(1, Location::RequiresFpuRegister());
   summary->set_out(0, Location::RequiresFpuRegister());
   return summary;
@@ skipping 2183 matching lines @@
         left.reg(), right.reg(), needs_number_check(), token_pos(), deopt_id_);
   }
   if (kind() != Token::kEQ_STRICT) {
     ASSERT(kind() == Token::kNE_STRICT);
     true_condition = NegateCondition(true_condition);
   }
   return true_condition;
 }
 
 
-void StrictCompareInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
-  __ Comment("StrictCompareInstr");
-  ASSERT(kind() == Token::kEQ_STRICT || kind() == Token::kNE_STRICT);
-
+void ComparisonInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   Label is_true, is_false;
   BranchLabels labels = {&is_true, &is_false, &is_false};
   Condition true_condition = EmitComparisonCode(compiler, labels);
-  EmitBranchOnCondition(compiler, true_condition, labels);
+  const Register result = this->locs()->out(0).reg();
 
-  const Register result = locs()->out(0).reg();
+  // TODO(dartbug.com/29908): Use csel here for better branch prediction?
+  if (true_condition != kInvalidCondition) {
+    EmitBranchOnCondition(compiler, true_condition, labels);
+  }
   Label done;
   __ Bind(&is_false);
   __ LoadObject(result, Bool::False());
   __ b(&done);
   __ Bind(&is_true);
   __ LoadObject(result, Bool::True());
   __ Bind(&done);
 }
 
 
-void StrictCompareInstr::EmitBranchCode(FlowGraphCompiler* compiler,
-                                        BranchInstr* branch) {
-  ASSERT(kind() == Token::kEQ_STRICT || kind() == Token::kNE_STRICT);
-
+void ComparisonInstr::EmitBranchCode(FlowGraphCompiler* compiler,
+                                     BranchInstr* branch) {
   BranchLabels labels = compiler->CreateBranchLabels(branch);
   Condition true_condition = EmitComparisonCode(compiler, labels);
-  EmitBranchOnCondition(compiler, true_condition, labels);
+  if (true_condition != kInvalidCondition) {
+    EmitBranchOnCondition(compiler, true_condition, labels);
+  }
 }
 
 
 LocationSummary* BooleanNegateInstr::MakeLocationSummary(Zone* zone,
                                                          bool opt) const {
   return LocationSummary::Make(zone, 1, Location::RequiresRegister(),
                                LocationSummary::kNoCall);
 }
 
 
@@ skipping 53 matching lines @@
   compiler->GenerateRuntimeCall(TokenPosition::kNoSource, deopt_id(),
                                 kGrowRegExpStackRuntimeEntry, 1, locs());
   __ Drop(1);
   __ Pop(result);
 }
 
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM64