[wasm] Reuse constrained input for same vreg

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 a5f72c70b230320108f454b9fd62fa654d51467f..45aa782a4ff77b8355c18ff426692739f44a3758 100644
--- a/src/compiler/ia32/instruction-selector-ia32.cc
+++ b/src/compiler/ia32/instruction-selector-ia32.cc
@@ -763,20 +763,27 @@ void InstructionSelector::VisitInt32PairMul(Node* node) {
 
   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)};
+    Node* lout = node;
+    Node* hout = NodeProperties::FindProjection(node, 1);
+    int temp1 = g.AllocateVirtualRegister();
+    int temp2 = g.AllocateVirtualRegister();
+    int temp3 = g.AllocateVirtualRegister();
+    int temp4 = g.AllocateVirtualRegister();
+
+    Emit(kIA32Imul, g.DefineAsFixedForVreg(temp1, ecx),
+         g.UseFixed(node->InputAt(3), ecx), g.Use(node->InputAt(0)));
+    Emit(kIA32Imul, g.DefineAsFixedForVreg(temp2, edx),
+         g.UseFixed(node->InputAt(1), edx), g.Use(node->InputAt(2)));
+    Emit(kIA32Add, g.DefineAsFixedForVreg(temp3, ecx),
+         g.UseFixedForVreg(temp2, ecx), g.UseRegisterForVreg(temp1));
+    InstructionOperand outputs[] = {g.DefineAsFixed(lout, eax),
+                                    g.DefineAsFixedForVreg(temp4, edx)};
+    InstructionOperand inputs[] = {g.UseUniqueRegister(node->InputAt(0)),
+                                   g.UseUniqueRegister(node->InputAt(2))};
+    Emit(kIA32Umul, 2, outputs, 2, inputs);
+    Emit(kIA32Add, g.DefineAsFixed(hout, ecx), g.UseFixedForVreg(temp3, ecx),
+         g.UseRegisterForVreg(temp4));
 
-    InstructionOperand outputs[] = {
-        g.DefineAsFixed(node, eax),
-        g.DefineAsFixed(NodeProperties::FindProjection(node, 1), ecx)};
-
-    InstructionOperand temps[] = {g.TempRegister(edx)};
-
-    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.