Change the order of blocking in AllocateRegistersLocally.

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 14e4dd9eefce52ffe4ee45b8f113b873b3559c9d..45c9e7351ef644a02d67293085405bc5e0f677c2 100644
--- a/runtime/vm/flow_graph_compiler.cc
+++ b/runtime/vm/flow_graph_compiler.cc
@@ -729,20 +729,15 @@ void FlowGraphCompiler::AllocateRegistersLocally(Instruction* instr) {
   bool blocked_registers[kNumberOfCpuRegisters];
 
   // Mark all available registers free.
-  for (intptr_t i = 0; i < kFirstFreeCpuRegister; i++) {
-    blocked_registers[i] = true;
-  }
-  for (intptr_t i = kFirstFreeCpuRegister; i <= kLastFreeCpuRegister; i++) {
+  for (intptr_t i = 0; i < kNumberOfCpuRegisters; i++) {
     blocked_registers[i] = false;
   }
-  for (intptr_t i = kLastFreeCpuRegister + 1; i < kNumberOfCpuRegisters; i++) {
-    blocked_registers[i] = true;
-  }
 
   // Mark all fixed input, temp and output registers as used.
   for (intptr_t i = 0; i < locs->input_count(); i++) {
     Location loc = locs->in(i);
     if (loc.IsRegister()) {
+      // Check that a register is not specified twice in the summary.
       ASSERT(!blocked_registers[loc.reg()]);
       blocked_registers[loc.reg()] = true;
     }
@@ -751,6 +746,7 @@ void FlowGraphCompiler::AllocateRegistersLocally(Instruction* instr) {
   for (intptr_t i = 0; i < locs->temp_count(); i++) {
     Location loc = locs->temp(i);
     if (loc.IsRegister()) {
+      // Check that a register is not specified twice in the summary.
       ASSERT(!blocked_registers[loc.reg()]);
       blocked_registers[loc.reg()] = true;
     }
@@ -773,6 +769,14 @@ void FlowGraphCompiler::AllocateRegistersLocally(Instruction* instr) {
     blocked_registers[PP] = true;
   }
 
+  // Block all non-free registers.
+  for (intptr_t i = 0; i < kFirstFreeCpuRegister; i++) {
+    blocked_registers[i] = true;
+  }
+  for (intptr_t i = kLastFreeCpuRegister + 1; i < kNumberOfCpuRegisters; i++) {
+    blocked_registers[i] = true;
+  }
+
   // Allocate all unallocated input locations.
   const bool should_pop = !instr->IsPushArgument();
   for (intptr_t i = locs->input_count() - 1; i >= 0; i--) {