[Atomics] Make Atomics.exchange a builtin using TF

src/compiler/x64/code-generator-x64.cc

Index: src/compiler/x64/code-generator-x64.cc
diff --git a/src/compiler/x64/code-generator-x64.cc b/src/compiler/x64/code-generator-x64.cc
index cd4eeedf10dcec10fc9bc0aa34dda01645ca73e5..1970cded70fdf3fb66d33208f6f4f77b973ed224 100644
--- a/src/compiler/x64/code-generator-x64.cc
+++ b/src/compiler/x64/code-generator-x64.cc
@@ -2134,24 +2134,6 @@ CodeGenerator::CodeGenResult CodeGenerator::AssembleArchInstruction(
       }
       break;
     }
-    case kX64Xchgb: {
-      size_t index = 0;
-      Operand operand = i.MemoryOperand(&index);
-      __ xchgb(i.InputRegister(index), operand);
-      break;
-    }
-    case kX64Xchgw: {
-      size_t index = 0;
-      Operand operand = i.MemoryOperand(&index);
-      __ xchgw(i.InputRegister(index), operand);
-      break;
-    }
-    case kX64Xchgl: {
-      size_t index = 0;
-      Operand operand = i.MemoryOperand(&index);
-      __ xchgl(i.InputRegister(index), operand);
-      break;
-    }
     case kX64Int32x4Create: {
       CpuFeatureScope sse_scope(masm(), SSE4_1);
       XMMRegister dst = i.OutputSimd128Register();
@@ -2229,6 +2211,36 @@ CodeGenerator::CodeGenResult CodeGenerator::AssembleArchInstruction(
     case kX64StackCheck:
       __ CompareRoot(rsp, Heap::kStackLimitRootIndex);
       break;
+#define EXCHANGE_OPERANDS                \
+  size_t index = 0;                      \
+  Register r = i.InputRegister(index++); \
+  Operand operand = i.MemoryOperand(&index);
+    case kAtomicExchangeInt8: {
+      EXCHANGE_OPERANDS
+      __ xchgb(r, operand, true);

[binji, 2017/01/17 21:45:50]

just add the appropriate extension instruction here, rather than adding a param
to xchgb

[aseemgarg, 2017/01/21 08:40:37]

Done.

+      break;
+    }
+    case kAtomicExchangeUint8: {
+      EXCHANGE_OPERANDS
+      __ xchgb(r, operand, false);
+      break;
+    }
+    case kAtomicExchangeInt16: {
+      EXCHANGE_OPERANDS
+      __ xchgw(r, operand, true);
+      break;
+    }
+    case kAtomicExchangeUint16: {
+      EXCHANGE_OPERANDS
+      __ xchgw(r, operand, false);
+      break;
+    }
+    case kAtomicExchangeWord32: {
+      EXCHANGE_OPERANDS
+      __ xchgl(r, operand);
+      break;
+    }
+#undef EXCHANGE_OPERANDS
     case kAtomicLoadInt8:
     case kAtomicLoadUint8:
     case kAtomicLoadInt16: