Use GPRs for mints

runtime/vm/flow_graph_compiler_arm.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_ARM.
 #if defined(TARGET_ARCH_ARM)
 
 #include "vm/flow_graph_compiler.h"
 
 #include "vm/ast_printer.h"
@@ skipping 1428 matching lines @@
         DRegister d2 = OddDRegisterOf(fpu_reg);
         // TOOD(regis): merge stores using vstmd instruction.
         __ vstrd(d1, Address(SP, offset));
         __ vstrd(d2, Address(SP, offset + 2 * kWordSize));
         offset += kFpuRegisterSize;
       }
     }
     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();
   if (fpu_regs_count > 0) {
     // Fpu registers have the lowest register number at the lowest address.
     intptr_t offset = 0;
     for (intptr_t reg_idx = 0; reg_idx < kNumberOfFpuRegisters; ++reg_idx) {
       QRegister fpu_reg = static_cast<QRegister>(reg_idx);
       if (locs->live_registers()->ContainsFpuRegister(fpu_reg)) {
         DRegister d1 = EvenDRegisterOf(fpu_reg);
@@ skipping 339 matching lines @@
   DRegister dreg = EvenDRegisterOf(reg);
   __ vldrd(dreg, Address(SP, kDoubleSize, Address::PostIndex));
 }
 
 
 #undef __
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM