X87: [wasm] Int64Lowering of Int64Sub on ia32 and arm.

src/compiler/x87/code-generator-x87.cc

Index: src/compiler/x87/code-generator-x87.cc
diff --git a/src/compiler/x87/code-generator-x87.cc b/src/compiler/x87/code-generator-x87.cc
index a59a6ad978402cbfbc80b62bcc3df76138ce7999..3828e7d5cf0cd9ea564916f95ca458aab2eddbef 100644
--- a/src/compiler/x87/code-generator-x87.cc
+++ b/src/compiler/x87/code-generator-x87.cc
@@ -787,6 +787,31 @@ void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
       }
       break;
     }
+    case kX87SubPair: {
+      // i.OutputRegister(0) == i.InputRegister(0) ... left low word.
+      // i.InputRegister(1) ... left high word.
+      // i.InputRegister(2) ... right low word.
+      // i.InputRegister(3) ... right high word.
+      bool use_temp = false;
+      if (i.OutputRegister(0).code() == i.InputRegister(1).code() ||
+          i.OutputRegister(0).code() == i.InputRegister(3).code()) {
+        // We cannot write to the output register directly, because it would
+        // overwrite an input for adc. We have to use the temp register.
+        use_temp = true;
+        __ Move(i.TempRegister(0), i.InputRegister(0));
+        __ sub(i.TempRegister(0), i.InputRegister(2));
+      } else {
+        __ sub(i.OutputRegister(0), i.InputRegister(2));
+      }
+      __ sbb(i.InputRegister(1), Operand(i.InputRegister(3)));
+      if (i.OutputRegister(1).code() != i.InputRegister(1).code()) {
+        __ Move(i.OutputRegister(1), i.InputRegister(1));
+      }
+      if (use_temp) {
+        __ Move(i.OutputRegister(0), i.TempRegister(0));
+      }
+      break;
+    }
     case kX87ShlPair:
       if (HasImmediateInput(instr, 2)) {
         __ ShlPair(i.InputRegister(1), i.InputRegister(0), i.InputInt6(2));