Revert to use macro REG_MASK_BIT, now with parentheses.

runtime/vm/flow_graph_compiler.cc

Index: runtime/vm/flow_graph_compiler.cc
diff --git a/runtime/vm/flow_graph_compiler.cc b/runtime/vm/flow_graph_compiler.cc
index 640600225848c52e8b7ecfdbbf10209ce4be52b8..74af234a78d583fe98c7cf213ca3905b94cd4632 100644
--- a/runtime/vm/flow_graph_compiler.cc
+++ b/runtime/vm/flow_graph_compiler.cc
@@ -1190,19 +1190,15 @@ static Register AllocateFreeRegister(bool* blocked_registers) {
 }
 
 
-static uword RegMaskBit(Register reg) {
-  return ((reg) != kNoRegister) ? (1 << (reg)) : 0;
-}
-
-
+#define REG_MASK_BIT(reg) (((reg) != kNoRegister) ? (1 << (reg)) : 0)
 // Mask of globally reserved registers. Some other registers are only reserved
 // in particular code (e.g., ARGS_DESC_REG in intrinsics).
-static const uword kReservedCpuRegisters = RegMaskBit(SPREG)
-                                         | RegMaskBit(FPREG)
-                                         | RegMaskBit(TMP)
-                                         | RegMaskBit(TMP2)
-                                         | RegMaskBit(PP)
-                                         | RegMaskBit(THR);
+static const uword kReservedCpuRegisters = REG_MASK_BIT(SPREG)
+                                         | REG_MASK_BIT(FPREG)
+                                         | REG_MASK_BIT(TMP)
+                                         | REG_MASK_BIT(TMP2)
+                                         | REG_MASK_BIT(PP)
+                                         | REG_MASK_BIT(THR);
 
 
 void FlowGraphCompiler::AllocateRegistersLocally(Instruction* instr) {
@@ -1509,10 +1505,10 @@ ParallelMoveResolver::ScratchRegisterScope::ScratchRegisterScope(
     : resolver_(resolver),
       reg_(kNoRegister),
       spilled_(false) {
-  uword blocked_mask = RegMaskBit(blocked) | kReservedCpuRegisters;
+  uword blocked_mask = REG_MASK_BIT(blocked) | kReservedCpuRegisters;
   if (resolver->compiler_->intrinsic_mode()) {
     // Block additional registers that must be preserved for intrinsics.
-    blocked_mask |= RegMaskBit(ARGS_DESC_REG);
+    blocked_mask |= REG_MASK_BIT(ARGS_DESC_REG);
   }
   reg_ = static_cast<Register>(
       resolver_->AllocateScratchRegister(Location::kRegister,