Fix lazy deoptimization in the presence of exceptions

runtime/vm/intermediate_language_ia32.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_IA32.
 #if defined(TARGET_ARCH_IA32)
 
 #include "vm/intermediate_language.h"
 
 #include "vm/compiler.h"
 #include "vm/dart_entry.h"
 #include "vm/flow_graph.h"
 #include "vm/flow_graph_compiler.h"
 #include "vm/flow_graph_range_analysis.h"
+#include "vm/instructions.h"
 #include "vm/locations.h"
 #include "vm/object_store.h"
 #include "vm/parser.h"
 #include "vm/stack_frame.h"
 #include "vm/stub_code.h"
 #include "vm/symbols.h"
 
 #define __ compiler->assembler()->
 #define Z (compiler->zone())
 
@@ skipping 2515 matching lines @@
 
 
 LocationSummary* CatchBlockEntryInstr::MakeLocationSummary(Zone* zone,
                                                            bool opt) const {
   UNREACHABLE();
   return NULL;
 }
 
 
 void CatchBlockEntryInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
+  // Ensure space for patching return sites for lazy deopt.
+  __ nop(CallPattern::pattern_length_in_bytes());

[Florian Schneider, 2016/09/23 19:53:34]

Needed to ensure, patching a return-address does not overlap with a catch entry
block (also on x64). On ARM/MIPS/ARM64, there is always space after the call
(one instructions dropping the arguments)

[rmacnak, 2016/09/26 20:21:48]

Just noting that space might disappear on the RISC architectures with a register
calling convention.

[Florian Schneider, 2016/09/26 23:05:28]

Actually, I'll add space on ARM/MIPS archs as well. The call pattern can be up
to 5 instructions which may overlap with the entry.

Also, it only is needed in JIT mode, and in optimized code.

+
   __ Bind(compiler->GetJumpLabel(this));
   compiler->AddExceptionHandler(catch_try_index(),
                                 try_index(),
                                 compiler->assembler()->CodeSize(),
                                 catch_handler_types_,
                                 needs_stacktrace());
+  // On lazy deoptimization we patch the optimized code here to enter the
+  // deoptimization stub.
+  const intptr_t deopt_id = Thread::ToDeoptAfter(GetDeoptId());
+  if (compiler->is_optimizing()) {
+    compiler->AddDeoptIndexAtCall(deopt_id);
+  } else {
+    compiler->AddCurrentDescriptor(RawPcDescriptors::kDeopt,
+                                   deopt_id,
+                                   TokenPosition::kNoSource);
+  }
   if (HasParallelMove()) {
     compiler->parallel_move_resolver()->EmitNativeCode(parallel_move());
   }
 
   // Restore ESP from EBP as we are coming from a throw and the code for
   // popping arguments has not been run.
   const intptr_t fp_sp_dist =
       (kFirstLocalSlotFromFp + 1 - compiler->StackSize()) * kWordSize;
   ASSERT(fp_sp_dist <= 0);
   __ leal(ESP, Address(EBP, fp_sp_dist));
@@ skipping 4211 matching lines @@
   // EAX: Function.
   // EDX: Arguments descriptor array.
   // ECX: Smi 0 (no IC data; the lazy-compile stub expects a GC-safe value).
   __ xorl(ECX, ECX);
   __ call(EBX);
   compiler->RecordSafepoint(locs());
   // Marks either the continuation point in unoptimized code or the
   // deoptimization point in optimized code, after call.
   const intptr_t deopt_id_after = Thread::ToDeoptAfter(deopt_id());
   if (compiler->is_optimizing()) {
-    compiler->AddDeoptIndexAtCall(deopt_id_after, token_pos());
+    compiler->AddDeoptIndexAtCall(deopt_id_after);
   }
   // Add deoptimization continuation point after the call and before the
   // arguments are removed.
   // In optimized code this descriptor is needed for exception handling.
   compiler->AddCurrentDescriptor(RawPcDescriptors::kDeopt,
                                  deopt_id_after,
                                  token_pos());
   __ Drop(argument_count);
 }
 
@@ skipping 73 matching lines @@
   __ Drop(1);
   __ popl(result);
 }
 
 
 }  // namespace dart
 
 #undef __
 
 #endif  // defined TARGET_ARCH_IA32