Clobber non-live temporaries on some paths involving a possible slow-path allocation.

runtime/vm/flow_graph_compiler_arm64.cc

 // Copyright (c) 2014, 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_ARM64.
 #if defined(TARGET_ARCH_ARM64)
 
 #include "vm/flow_graph_compiler.h"
 
 #include "vm/ast_printer.h"
@@ skipping 1410 matching lines @@
     __ CompareRegisters(left, right);
   }
 }
 
 
 // This function must be in sync with FlowGraphCompiler::RecordSafepoint and
 // FlowGraphCompiler::SlowPathEnvironmentFor.
 void FlowGraphCompiler::SaveLiveRegisters(LocationSummary* locs) {
 #if defined(DEBUG)
   locs->CheckWritableInputs();
+  ClobberDeadTempRegisters(locs);
 #endif
 
   // TODO(vegorov): consider saving only caller save (volatile) registers.
   const intptr_t fpu_regs_count = locs->live_registers()->FpuRegisterCount();
   if (fpu_regs_count > 0) {
     // Store fpu registers with the lowest register number at the lowest
     // address.
     for (intptr_t reg_idx = kNumberOfVRegisters - 1;
                   reg_idx >= 0; --reg_idx) {
       VRegister fpu_reg = static_cast<VRegister>(reg_idx);
       if (locs->live_registers()->ContainsFpuRegister(fpu_reg)) {
         __ PushQuad(fpu_reg);
       }
     }
   }
 
   // Store general purpose registers with the highest register number at the
   // lowest address. The order in which the registers are pushed must match the
   // order in which the registers are encoded in the safe point's stack map.
   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);
     }
   }
 }
 
 
 void FlowGraphCompiler::RestoreLiveRegisters(LocationSummary* locs) {
+#if defined(DEBUG)
+  ClobberDeadTempRegisters(locs);
+#endif
   // General purpose registers have the highest register number at the
   // lowest address.
   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.
     for (intptr_t reg_idx = 0; reg_idx < kNumberOfVRegisters; ++reg_idx) {
       VRegister fpu_reg = static_cast<VRegister>(reg_idx);
       if (locs->live_registers()->ContainsFpuRegister(fpu_reg)) {
         __ PopQuad(fpu_reg);
       }
     }
   }
 }
 
 
+#if defined(DEBUG)
+void FlowGraphCompiler::ClobberDeadTempRegisters(LocationSummary* locs) {
+  // Clobber temporaries that have not been manually preserved.
+  for (intptr_t i = 0; i < locs->temp_count(); ++i) {
+    Location tmp = locs->temp(i);
+    // TODO(zerny): clobber non-live temporary FPU registers.
+    if (tmp.IsRegister() &&
+        !locs->live_registers()->ContainsRegister(tmp.reg())) {
+      __ movz(tmp.reg(), Immediate(0xf7), 0);
+    }
+  }
+}
+#endif
+
+
 void FlowGraphCompiler::EmitTestAndCall(const ICData& ic_data,
                                         Register class_id_reg,
                                         intptr_t argument_count,
                                         const Array& argument_names,
                                         Label* deopt,
                                         intptr_t deopt_id,
                                         intptr_t token_index,
                                         LocationSummary* locs) {
   ASSERT(is_optimizing());
   ASSERT(!ic_data.IsNull() && (ic_data.NumberOfUsedChecks() > 0));
@@ skipping 316 matching lines @@
 void ParallelMoveResolver::RestoreFpuScratch(FpuRegister reg) {
   __ PopDouble(reg);
 }
 
 
 #undef __
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM64