[wasm] Int64Lowering of Int64Add 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 482376d6aa15851c9e2b32ce6f6706e513475324..a230beac93f4e8cecce1c1405ca119d7c3e30c08 100644
--- a/src/compiler/ia32/code-generator-ia32.cc
+++ b/src/compiler/ia32/code-generator-ia32.cc
@@ -680,6 +680,14 @@ void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
         __ sar_cl(i.OutputOperand());
       }
       break;
+    case kIA32AddPair:
+      // i.OutputRegister(0) == i.InputRegister(0) ... left low word.
+      // i.OutputRegister(1) == i.InputRegister(1) ... left high word.
+      // i.InputRegister(2) ... right low word.
+      // i.InputRegister(3) ... right high word.
+      __ add(i.OutputRegister(0), i.InputRegister(2));
+      __ adc(i.OutputRegister(1), Operand(i.InputRegister(3)));
+      break;
     case kIA32PairShl:
       if (HasImmediateInput(instr, 2)) {
         __ PairShl(i.InputRegister(1), i.InputRegister(0), i.InputInt6(2));