Fix lazy deoptimization in the presence of exceptions

runtime/vm/intermediate_language_ia32.cc

Index: runtime/vm/intermediate_language_ia32.cc
diff --git a/runtime/vm/intermediate_language_ia32.cc b/runtime/vm/intermediate_language_ia32.cc
index 1595297274d20bf943469181f58d63b28494b2ad..2d0a4c2860909633c0d7cac0f44a774bc9734f4d 100644
--- a/runtime/vm/intermediate_language_ia32.cc
+++ b/runtime/vm/intermediate_language_ia32.cc
@@ -12,6 +12,7 @@
 #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"
@@ -2547,12 +2548,25 @@ LocationSummary* CatchBlockEntryInstr::MakeLocationSummary(Zone* zone,
 
 
 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());
   }
@@ -6784,7 +6798,7 @@ void ClosureCallInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   // 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.