[turbofan] Don't generate unnecessary minus zero checks.

src/compiler/effect-control-linearizer.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/effect-control-linearizer.h"
 
 #include "src/code-factory.h"
 #include "src/compiler/access-builder.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/linkage.h"
@@ skipping 1514 matching lines @@
   Node* is_safe =
       graph()->NewNode(machine()->Uint32LessThanOrEqual(), value, max_int);
   control = effect = graph()->NewNode(
       common()->DeoptimizeUnless(DeoptimizeReason::kLostPrecision), is_safe,
       frame_state, effect, control);
 
   return ValueEffectControl(value, effect, control);
 }
 
 EffectControlLinearizer::ValueEffectControl
-EffectControlLinearizer::BuildCheckedFloat64ToInt32(Node* value,
+EffectControlLinearizer::BuildCheckedFloat64ToInt32(CheckForMinusZeroMode mode,
+                                                    Node* value,
                                                     Node* frame_state,
                                                     Node* effect,
                                                     Node* control) {
   Node* value32 = graph()->NewNode(machine()->RoundFloat64ToInt32(), value);
   Node* check_same = graph()->NewNode(
       machine()->Float64Equal(), value,
       graph()->NewNode(machine()->ChangeInt32ToFloat64(), value32));
   control = effect = graph()->NewNode(
       common()->DeoptimizeUnless(DeoptimizeReason::kLostPrecisionOrNaN),
       check_same, frame_state, effect, control);
 
-  // Check if {value} is -0.
-  Node* check_zero = graph()->NewNode(machine()->Word32Equal(), value32,
-                                      jsgraph()->Int32Constant(0));
-  Node* branch_zero = graph()->NewNode(common()->Branch(BranchHint::kFalse),
-                                       check_zero, control);
+  if (mode == CheckForMinusZeroMode::kCheckForMinusZero) {
+    // Check if {value} is -0.
+    Node* check_zero = graph()->NewNode(machine()->Word32Equal(), value32,
+                                        jsgraph()->Int32Constant(0));
+    Node* branch_zero = graph()->NewNode(common()->Branch(BranchHint::kFalse),
+                                         check_zero, control);
 
-  Node* if_zero = graph()->NewNode(common()->IfTrue(), branch_zero);
-  Node* if_notzero = graph()->NewNode(common()->IfFalse(), branch_zero);
+    Node* if_zero = graph()->NewNode(common()->IfTrue(), branch_zero);
+    Node* if_notzero = graph()->NewNode(common()->IfFalse(), branch_zero);
 
-  // In case of 0, we need to check the high bits for the IEEE -0 pattern.
-  Node* check_negative = graph()->NewNode(
-      machine()->Int32LessThan(),
-      graph()->NewNode(machine()->Float64ExtractHighWord32(), value),
-      jsgraph()->Int32Constant(0));
+    // In case of 0, we need to check the high bits for the IEEE -0 pattern.
+    Node* check_negative = graph()->NewNode(
+        machine()->Int32LessThan(),
+        graph()->NewNode(machine()->Float64ExtractHighWord32(), value),
+        jsgraph()->Int32Constant(0));
 
-  Node* deopt_minus_zero =
-      graph()->NewNode(common()->DeoptimizeIf(DeoptimizeReason::kMinusZero),
-                       check_negative, frame_state, effect, if_zero);
+    Node* deopt_minus_zero =
+        graph()->NewNode(common()->DeoptimizeIf(DeoptimizeReason::kMinusZero),
+                         check_negative, frame_state, effect, if_zero);
 
-  Node* merge =
-      graph()->NewNode(common()->Merge(2), deopt_minus_zero, if_notzero);
+    control =
+        graph()->NewNode(common()->Merge(2), deopt_minus_zero, if_notzero);
+    effect = graph()->NewNode(common()->EffectPhi(2), deopt_minus_zero, effect,
+                              control);
+  }
 
-  effect =
-      graph()->NewNode(common()->EffectPhi(2), deopt_minus_zero, effect, merge);
-
-  return ValueEffectControl(value32, effect, merge);
+  return ValueEffectControl(value32, effect, control);
 }
 
 EffectControlLinearizer::ValueEffectControl
 EffectControlLinearizer::LowerCheckedFloat64ToInt32(Node* node,
                                                     Node* frame_state,
                                                     Node* effect,
                                                     Node* control) {
+  CheckForMinusZeroMode mode = CheckMinusZeroModeOf(node->op());
   Node* value = node->InputAt(0);
 
-  return BuildCheckedFloat64ToInt32(value, frame_state, effect, control);
+  return BuildCheckedFloat64ToInt32(mode, value, frame_state, effect, control);
 }
 
 EffectControlLinearizer::ValueEffectControl
 EffectControlLinearizer::LowerCheckedTaggedSignedToInt32(Node* node,
                                                          Node* frame_state,
                                                          Node* effect,
                                                          Node* control) {
   Node* value = node->InputAt(0);
 
   Node* check = ObjectIsSmi(value);
   control = effect =
       graph()->NewNode(common()->DeoptimizeUnless(DeoptimizeReason::kNotASmi),
                        check, frame_state, effect, control);
   value = ChangeSmiToInt32(value);
 
   return ValueEffectControl(value, effect, control);
 }
 
 EffectControlLinearizer::ValueEffectControl
 EffectControlLinearizer::LowerCheckedTaggedToInt32(Node* node,
                                                    Node* frame_state,
                                                    Node* effect,
                                                    Node* control) {
+  CheckForMinusZeroMode mode = CheckMinusZeroModeOf(node->op());
   Node* value = node->InputAt(0);
 
   Node* check = ObjectIsSmi(value);
   Node* branch =
       graph()->NewNode(common()->Branch(BranchHint::kTrue), check, control);
 
   // In the Smi case, just convert to int32.
   Node* if_true = graph()->NewNode(common()->IfTrue(), branch);
   Node* etrue = effect;
   Node* vtrue = ChangeSmiToInt32(value);
 
   // In the non-Smi case, check the heap numberness, load the number and convert
   // to int32.
   Node* if_false = graph()->NewNode(common()->IfFalse(), branch);
   Node* efalse = effect;
   Node* vfalse;
   {
     Node* value_map = efalse =
         graph()->NewNode(simplified()->LoadField(AccessBuilder::ForMap()),
                          value, efalse, if_false);
     Node* check = graph()->NewNode(machine()->WordEqual(), value_map,
                                    jsgraph()->HeapNumberMapConstant());
     if_false = efalse = graph()->NewNode(
         common()->DeoptimizeUnless(DeoptimizeReason::kNotAHeapNumber), check,
         frame_state, efalse, if_false);
     vfalse = efalse = graph()->NewNode(
         simplified()->LoadField(AccessBuilder::ForHeapNumberValue()), value,
         efalse, if_false);
     ValueEffectControl state =
-        BuildCheckedFloat64ToInt32(vfalse, frame_state, efalse, if_false);
+        BuildCheckedFloat64ToInt32(mode, vfalse, frame_state, efalse, if_false);
     if_false = state.control;
     efalse = state.effect;
     vfalse = state.value;
   }
 
   control = graph()->NewNode(common()->Merge(2), if_true, if_false);
   effect = graph()->NewNode(common()->EffectPhi(2), etrue, efalse, control);
   value = graph()->NewNode(common()->Phi(MachineRepresentation::kWord32, 2),
                            vtrue, vfalse, control);
 
@@ skipping 1068 matching lines @@
         isolate(), graph()->zone(), callable.descriptor(), 0, flags,
         Operator::kNoThrow);
     to_number_operator_.set(common()->Call(desc));
   }
   return to_number_operator_.get();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8