[wasm] Trim graph before scheduling.

src/compiler/ia32/instruction-selector-ia32.cc

Index: src/compiler/ia32/instruction-selector-ia32.cc
diff --git a/src/compiler/ia32/instruction-selector-ia32.cc b/src/compiler/ia32/instruction-selector-ia32.cc
index 7e98023f5dfacf81cc344199e08910ee84191f47..e710c8529534f3e8a7d010c7159ea6ffad6a5a9f 100644
--- a/src/compiler/ia32/instruction-selector-ia32.cc
+++ b/src/compiler/ia32/instruction-selector-ia32.cc
@@ -646,55 +646,78 @@ void InstructionSelector::VisitWord32Sar(Node* node) {
 void InstructionSelector::VisitInt32PairAdd(Node* node) {
   IA32OperandGenerator g(this);
 
-  // We use UseUniqueRegister here to avoid register sharing with the temp
-  // register.
-  InstructionOperand inputs[] = {
-      g.UseRegister(node->InputAt(0)), g.UseUniqueRegister(node->InputAt(1)),
-      g.UseRegister(node->InputAt(2)), g.UseUniqueRegister(node->InputAt(3))};
+  Node* projection1 = NodeProperties::FindProjection(node, 1);
+  if (projection1) {
+    // We use UseUniqueRegister here to avoid register sharing with the temp
+    // register.
+    InstructionOperand inputs[] = {
+        g.UseRegister(node->InputAt(0)), g.UseUniqueRegister(node->InputAt(1)),
+        g.UseRegister(node->InputAt(2)), g.UseUniqueRegister(node->InputAt(3))};
 
-  InstructionOperand outputs[] = {
-      g.DefineSameAsFirst(node),
-      g.DefineAsRegister(NodeProperties::FindProjection(node, 1))};
+    InstructionOperand outputs[] = {g.DefineSameAsFirst(node),
+                                    g.DefineAsRegister(projection1)};
 
-  InstructionOperand temps[] = {g.TempRegister()};
+    InstructionOperand temps[] = {g.TempRegister()};
 
-  Emit(kIA32AddPair, 2, outputs, 4, inputs, 1, temps);
+    Emit(kIA32AddPair, 2, outputs, 4, inputs, 1, temps);
+  } else {
+    // The high word of the result is not used, so we emit the standard 32 bit
+    // instruction.
+    Emit(kIA32Add, g.DefineSameAsFirst(node), g.UseRegister(node->InputAt(0)),
+         g.Use(node->InputAt(2)));
+  }
 }
 
 void InstructionSelector::VisitInt32PairSub(Node* node) {
   IA32OperandGenerator g(this);
 
-  // We use UseUniqueRegister here to avoid register sharing with the temp
-  // register.
-  InstructionOperand inputs[] = {
-      g.UseRegister(node->InputAt(0)), g.UseUniqueRegister(node->InputAt(1)),
-      g.UseRegister(node->InputAt(2)), g.UseUniqueRegister(node->InputAt(3))};
+  Node* projection1 = NodeProperties::FindProjection(node, 1);
+  if (projection1) {
+    // We use UseUniqueRegister here to avoid register sharing with the temp
+    // register.
+    InstructionOperand inputs[] = {
+        g.UseRegister(node->InputAt(0)), g.UseUniqueRegister(node->InputAt(1)),
+        g.UseRegister(node->InputAt(2)), g.UseUniqueRegister(node->InputAt(3))};
 
-  InstructionOperand outputs[] = {
-      g.DefineSameAsFirst(node),
-      g.DefineAsRegister(NodeProperties::FindProjection(node, 1))};
+    InstructionOperand outputs[] = {g.DefineSameAsFirst(node),
+                                    g.DefineAsRegister(projection1)};
 
-  InstructionOperand temps[] = {g.TempRegister()};
+    InstructionOperand temps[] = {g.TempRegister()};
 
-  Emit(kIA32SubPair, 2, outputs, 4, inputs, 1, temps);
+    Emit(kIA32SubPair, 2, outputs, 4, inputs, 1, temps);
+  } else {
+    // The high word of the result is not used, so we emit the standard 32 bit
+    // instruction.
+    Emit(kIA32Sub, g.DefineSameAsFirst(node), g.UseRegister(node->InputAt(0)),
+         g.Use(node->InputAt(2)));
+  }
 }
 
 void InstructionSelector::VisitInt32PairMul(Node* node) {
   IA32OperandGenerator g(this);
 
-  // InputAt(3) explicitly shares ecx with OutputRegister(1) to save one
-  // register and one mov instruction.
-  InstructionOperand inputs[] = {
-      g.UseUnique(node->InputAt(0)), g.UseUnique(node->InputAt(1)),
-      g.UseUniqueRegister(node->InputAt(2)), g.UseFixed(node->InputAt(3), ecx)};
+  Node* projection1 = NodeProperties::FindProjection(node, 1);
+  if (projection1) {
+    // InputAt(3) explicitly shares ecx with OutputRegister(1) to save one
+    // register and one mov instruction.
+    InstructionOperand inputs[] = {g.UseUnique(node->InputAt(0)),
+                                   g.UseUnique(node->InputAt(1)),
+                                   g.UseUniqueRegister(node->InputAt(2)),
+                                   g.UseFixed(node->InputAt(3), ecx)};
 
-  InstructionOperand outputs[] = {
-      g.DefineAsFixed(node, eax),
-      g.DefineAsFixed(NodeProperties::FindProjection(node, 1), ecx)};
+    InstructionOperand outputs[] = {
+        g.DefineAsFixed(node, eax),
+        g.DefineAsFixed(NodeProperties::FindProjection(node, 1), ecx)};
 
-  InstructionOperand temps[] = {g.TempRegister(edx)};
+    InstructionOperand temps[] = {g.TempRegister(edx)};
 
-  Emit(kIA32MulPair, 2, outputs, 4, inputs, 1, temps);
+    Emit(kIA32MulPair, 2, outputs, 4, inputs, 1, temps);
+  } else {
+    // The high word of the result is not used, so we emit the standard 32 bit
+    // instruction.
+    Emit(kIA32Imul, g.DefineSameAsFirst(node), g.UseRegister(node->InputAt(0)),
+         g.Use(node->InputAt(2)));
+  }
 }
 
 void VisitWord32PairShift(InstructionSelector* selector, InstructionCode opcode,
@@ -712,11 +735,15 @@ void VisitWord32PairShift(InstructionSelector* selector, InstructionCode opcode,
                                  g.UseFixed(node->InputAt(1), edx),
                                  shift_operand};
 
-  InstructionOperand outputs[] = {
-      g.DefineAsFixed(node, eax),
-      g.DefineAsFixed(NodeProperties::FindProjection(node, 1), edx)};
+  InstructionOperand outputs[2];
+  int32_t output_count = 0;
+  outputs[output_count++] = g.DefineAsFixed(node, eax);
+  Node* projection1 = NodeProperties::FindProjection(node, 1);
+  if (projection1) {
+    outputs[output_count++] = g.DefineAsFixed(projection1, edx);

[titzer, 2016/10/19 09:20:42]

This doesn't seem quite right. Isn't edx overwritten, even if the result is not
used?

[ahaas, 2016/10/19 09:59:19]

We always use edx because it is one of the input registers. If projection1
exists, then we also define edx as an output register.

[titzer, 2016/10/19 11:07:08]

That's what I mean. Shouldn't we always mark edx as clobbered so that the
register allocator knows?

+  }
 
-  selector->Emit(opcode, 2, outputs, 3, inputs);
+  selector->Emit(opcode, output_count, outputs, 3, inputs);
 }
 
 void InstructionSelector::VisitWord32PairShl(Node* node) {