From 81e730e5f11a4ad2d0ba90edf2530d5f00989af9 Mon Sep 17 00:00:00 2001
From: Vladimir Ivanov <vlivanov@openjdk.org>
Date: Mon, 25 Jan 2021 20:02:56 +0000
Subject: [PATCH] 8259276: C2: Empty expression stack when reexecuting
 tableswitch/lookupswitch instructions after deoptimization

Reviewed-by: dlong, kvn, thartmann
---
 src/hotspot/share/opto/graphKit.cpp | 12 +++++++++---
 src/hotspot/share/opto/parse2.cpp   | 12 ++++++++----
 2 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/src/hotspot/share/opto/graphKit.cpp b/src/hotspot/share/opto/graphKit.cpp
index 14c3807d2e2..31668b880c2 100644
--- a/src/hotspot/share/opto/graphKit.cpp
+++ b/src/hotspot/share/opto/graphKit.cpp
@@ -823,8 +823,7 @@ bool GraphKit::dead_locals_are_killed() {
 
 #endif //ASSERT
 
-// Helper function for enforcing certain bytecodes to reexecute if
-// deoptimization happens
+// Helper function for enforcing certain bytecodes to reexecute if deoptimization happens.
 static bool should_reexecute_implied_by_bytecode(JVMState *jvms, bool is_anewarray) {
   ciMethod* cur_method = jvms->method();
   int       cur_bci   = jvms->bci();
@@ -839,8 +838,9 @@ static bool should_reexecute_implied_by_bytecode(JVMState *jvms, bool is_anewarr
     // is limited by dimensions and guarded by flag so in some cases
     // multianewarray() runtime calls will be generated and
     // the bytecode should not be reexecutes (stack will not be reset).
-  } else
+  } else {
     return false;
+  }
 }
 
 // Helper function for adding JVMState and debug information to node
@@ -894,6 +894,12 @@ void GraphKit::add_safepoint_edges(SafePointNode* call, bool must_throw) {
   // deoptimization happens. We set the reexecute state for them here
   if (out_jvms->is_reexecute_undefined() && //don't change if already specified
       should_reexecute_implied_by_bytecode(out_jvms, call->is_AllocateArray())) {
+#ifdef ASSERT
+    int inputs = 0, not_used; // initialized by GraphKit::compute_stack_effects()
+    assert(method() == youngest_jvms->method(), "sanity");
+    assert(compute_stack_effects(inputs, not_used), "unknown bytecode: %s", Bytecodes::name(java_bc()));
+    assert(out_jvms->sp() >= (uint)inputs, "not enough operands for reexecution");
+#endif // ASSERT
     out_jvms->set_should_reexecute(true); //NOTE: youngest_jvms not changed
   }
 
diff --git a/src/hotspot/share/opto/parse2.cpp b/src/hotspot/share/opto/parse2.cpp
index c006de2ae5a..9d89184db10 100644
--- a/src/hotspot/share/opto/parse2.cpp
+++ b/src/hotspot/share/opto/parse2.cpp
@@ -419,7 +419,6 @@ static void merge_ranges(SwitchRange* ranges, int& rp) {
 
 //-------------------------------do_tableswitch--------------------------------
 void Parse::do_tableswitch() {
-  Node* lookup = pop();
   // Get information about tableswitch
   int default_dest = iter().get_dest_table(0);
   int lo_index     = iter().get_int_table(1);
@@ -429,6 +428,7 @@ void Parse::do_tableswitch() {
   if (len < 1) {
     // If this is a backward branch, add safepoint
     maybe_add_safepoint(default_dest);
+    pop(); // the effect of the instruction execution on the operand stack
     merge(default_dest);
     return;
   }
@@ -485,22 +485,24 @@ void Parse::do_tableswitch() {
   }
 
   // Safepoint in case if backward branch observed
-  if( makes_backward_branch && UseLoopSafepoints )
+  if (makes_backward_branch && UseLoopSafepoints) {
     add_safepoint();
+  }
 
+  Node* lookup = pop(); // lookup value
   jump_switch_ranges(lookup, &ranges[0], &ranges[rp]);
 }
 
 
 //------------------------------do_lookupswitch--------------------------------
 void Parse::do_lookupswitch() {
-  Node *lookup = pop();         // lookup value
   // Get information about lookupswitch
   int default_dest = iter().get_dest_table(0);
   int len          = iter().get_int_table(1);
 
   if (len < 1) {    // If this is a backward branch, add safepoint
     maybe_add_safepoint(default_dest);
+    pop(); // the effect of the instruction execution on the operand stack
     merge(default_dest);
     return;
   }
@@ -577,9 +579,11 @@ void Parse::do_lookupswitch() {
   }
 
   // Safepoint in case backward branch observed
-  if (makes_backward_branch && UseLoopSafepoints)
+  if (makes_backward_branch && UseLoopSafepoints) {
     add_safepoint();
+  }
 
+  Node *lookup = pop(); // lookup value
   jump_switch_ranges(lookup, &ranges[0], &ranges[rp]);
 }