[Atomics] Make Atomics.exchange a builtin using TF

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

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/code-generator.h"
 
 #include "src/compilation-info.h"
 #include "src/compiler/code-generator-impl.h"
 #include "src/compiler/gap-resolver.h"
 #include "src/compiler/node-matchers.h"
@@ skipping 1870 matching lines @@
       break;
     case kIA32Poke: {
       int const slot = MiscField::decode(instr->opcode());
       if (HasImmediateInput(instr, 0)) {
         __ mov(Operand(esp, slot * kPointerSize), i.InputImmediate(0));
       } else {
         __ mov(Operand(esp, slot * kPointerSize), i.InputRegister(0));
       }
       break;
     }
-    case kIA32Xchgb: {
-      size_t index = 0;
-      Operand operand = i.MemoryOperand(&index);
-      __ xchg_b(i.InputRegister(index), operand);
-      break;
-    }
-    case kIA32Xchgw: {
-      size_t index = 0;
-      Operand operand = i.MemoryOperand(&index);
-      __ xchg_w(i.InputRegister(index), operand);
-      break;
-    }
-    case kIA32Xchgl: {
-      size_t index = 0;
-      Operand operand = i.MemoryOperand(&index);
-      __ xchg(i.InputRegister(index), operand);
-      break;
-    }
     case kCheckedLoadInt8:
       ASSEMBLE_CHECKED_LOAD_INTEGER(movsx_b);
       break;
     case kCheckedLoadUint8:
       ASSEMBLE_CHECKED_LOAD_INTEGER(movzx_b);
       break;
     case kCheckedLoadInt16:
       ASSEMBLE_CHECKED_LOAD_INTEGER(movsx_w);
       break;
     case kCheckedLoadUint16:
@@ skipping 26 matching lines @@
     case kIA32StackCheck: {
       ExternalReference const stack_limit =
           ExternalReference::address_of_stack_limit(isolate());
       __ cmp(esp, Operand::StaticVariable(stack_limit));
       break;
     }
     case kCheckedLoadWord64:
     case kCheckedStoreWord64:
       UNREACHABLE();  // currently unsupported checked int64 load/store.
       break;
+#define EXCHANGE_OPERANDS                \
+  size_t index = 0;                      \
+  Register r = i.InputRegister(index++); \
+  Operand operand = i.MemoryOperand(&index);

[binji, 2017/02/22 02:08:38]

looks like if index is not used afterward it is simpler to just use
i.InputRegister(0) and i.MemoryOperand(1), then you can ditch the macro (as it
doesn't seem to be a common pattern in this file)

[aseemgarg, 2017/02/22 03:29:02]

Done.

+    case kAtomicExchangeInt8: {
+      EXCHANGE_OPERANDS
+      __ xchg_b(r, operand);
+      __ movsx_b(r, r);
+      break;
+    }
+    case kAtomicExchangeUint8: {
+      EXCHANGE_OPERANDS
+      __ xchg_b(r, operand);
+      __ movzx_b(r, r);
+      break;
+    }
+    case kAtomicExchangeInt16: {
+      EXCHANGE_OPERANDS
+      __ xchg_w(r, operand);
+      __ movsx_w(r, r);
+      break;
+    }
+    case kAtomicExchangeUint16: {
+      EXCHANGE_OPERANDS
+      __ xchg_w(r, operand);
+      __ movzx_w(r, r);
+      break;
+    }
+    case kAtomicExchangeWord32: {
+      EXCHANGE_OPERANDS
+      __ xchg(r, operand);
+      break;
+    }
+#undef EXCHANGE_OPERANDS
     case kAtomicLoadInt8:
     case kAtomicLoadUint8:
     case kAtomicLoadInt16:
     case kAtomicLoadUint16:
     case kAtomicLoadWord32:
     case kAtomicStoreWord8:
     case kAtomicStoreWord16:
     case kAtomicStoreWord32:
       UNREACHABLE();  // Won't be generated by instruction selector.
       break;
@@ skipping 701 matching lines @@
     int padding_size = last_lazy_deopt_pc_ + space_needed - current_pc;
     __ Nop(padding_size);
   }
 }
 
 #undef __
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8