[wasm] Int64Lowering of Int64Mul on ia32 and arm.

src/compiler/ia32/code-generator-ia32.cc

Index: src/compiler/ia32/code-generator-ia32.cc
diff --git a/src/compiler/ia32/code-generator-ia32.cc b/src/compiler/ia32/code-generator-ia32.cc
index 4dc01b43208bbda09227834c32f00ba80f9f7dbf..de486d1691b93040eb74d9fe1ec45bb76455d4a0 100644
--- a/src/compiler/ia32/code-generator-ia32.cc
+++ b/src/compiler/ia32/code-generator-ia32.cc
@@ -727,6 +727,18 @@ void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
       }
       break;
     }
+    case kIA32MulPair: {
+      __ imul(i.OutputRegister(1), i.InputOperand(0));
+      __ mov(i.TempRegister(0), i.InputOperand(1));
+      __ imul(i.TempRegister(0), i.InputOperand(2));
+      __ add(i.OutputRegister(1), i.TempRegister(0));
+      __ mov(i.OutputRegister(0), i.InputOperand(0));
+      // Multiplies the low words and stores them in eax and edx.
+      __ mul(i.InputRegister(2));
+      __ add(i.OutputRegister(1), i.TempRegister(0));
+
+      break;
+    }
     case kIA32ShlPair:
       if (HasImmediateInput(instr, 2)) {
         __ ShlPair(i.InputRegister(1), i.InputRegister(0), i.InputInt6(2));