Use GPRs for mints

runtime/vm/flow_graph_compiler_arm.cc

Index: runtime/vm/flow_graph_compiler_arm.cc
diff --git a/runtime/vm/flow_graph_compiler_arm.cc b/runtime/vm/flow_graph_compiler_arm.cc
index 3ea3503ba95bfacef7cba235ab2e64a48534c17c..17253e2f43c0b24b0e69b9939a7b2066a256c5c8 100644
--- a/runtime/vm/flow_graph_compiler_arm.cc
+++ b/runtime/vm/flow_graph_compiler_arm.cc
@@ -1446,23 +1446,25 @@ void FlowGraphCompiler::SaveLiveRegisters(LocationSummary* locs) {
     ASSERT(offset == (fpu_regs_count * kFpuRegisterSize));
   }
 
-  // Store general purpose registers with the lowest register number at the
+  // Store general purpose registers with the highest register number at the
   // lowest address.
-  const intptr_t cpu_registers = locs->live_registers()->cpu_registers();
-  ASSERT((cpu_registers & ~kAllCpuRegistersList) == 0);
-  if (cpu_registers != 0) {
-    __ PushList(cpu_registers);
+  for (intptr_t reg_idx = 0; reg_idx < kNumberOfCpuRegisters; ++reg_idx) {
+    Register reg = static_cast<Register>(reg_idx);
+    if (locs->live_registers()->ContainsRegister(reg)) {
+      __ Push(reg);
+    }

[regis, 2014/05/22 17:09:40]

Is there a good reason for this change? It should be documented.

[Cutch, 2014/05/23 21:33:54]

Yes, there was a very serious bug where the stackmap for a safepoint encoded
registers in the *opposite* order than __ PushList pushed them. This resulted in
random crashes during GC where a stack slot was expected to have an object (or
smi) but it had an untagged value. I've added a note in my cleanup CL:

https://codereview.chromium.org/299833011

[regis, 2014/05/23 22:36:59]

Cool you found it!

   }
 }
 
 
 void FlowGraphCompiler::RestoreLiveRegisters(LocationSummary* locs) {
-  // General purpose registers have the lowest register number at the
+  // General purpose registers have the highest register number at the
   // lowest address.
-  const intptr_t cpu_registers = locs->live_registers()->cpu_registers();
-  ASSERT((cpu_registers & ~kAllCpuRegistersList) == 0);
-  if (cpu_registers != 0) {
-    __ PopList(cpu_registers);
+  for (intptr_t reg_idx = kNumberOfCpuRegisters - 1; reg_idx >= 0; --reg_idx) {
+    Register reg = static_cast<Register>(reg_idx);
+    if (locs->live_registers()->ContainsRegister(reg)) {
+      __ Pop(reg);
+    }
   }
 
   const intptr_t fpu_regs_count = locs->live_registers()->FpuRegisterCount();