8303951: Add asserts before record_method_not_compilable where possible

Reviewed-by: kvn, thartmann

src/hotspot/share/compiler/compileBroker.cpp

@@ -2277,7 +2277,8 @@ void CompileBroker::invoke_compiler_on_method(CompileTask* task) {
     DirectivesStack::release(directive);
 
     if (!ci_env.failing() && !task->is_success()) {
-      //assert(false, "compiler should always document failure");
+      assert(ci_env.failure_reason() != nullptr, "expect failure reason");
+      assert(false, "compiler should always document failure: %s", ci_env.failure_reason());
       // The compiler elected, without comment, not to register a result.
       // Do not attempt further compilations of this method.
       ci_env.record_method_not_compilable("compile failed");

src/hotspot/share/opto/buildOopMap.cpp

@@ -251,7 +251,11 @@ OopMap *OopFlow::build_oop_map( Node *n, int max_reg, PhaseRegAlloc *regalloc, i
 
       // Check for a legal reg name in the oopMap and bailout if it is not.
       if (!omap->legal_vm_reg_name(r)) {
-        regalloc->C->record_method_not_compilable("illegal oopMap register name");
+        stringStream ss;
+        ss.print("illegal oopMap register name: ");
+        r->print_on(&ss);
+        assert(false, "%s", ss.as_string());
+        regalloc->C->record_method_not_compilable(ss.as_string());
         continue;
       }
       if( t->is_ptr()->_offset == 0 ) { // Not derived?
@@ -318,7 +322,11 @@ OopMap *OopFlow::build_oop_map( Node *n, int max_reg, PhaseRegAlloc *regalloc, i
       assert( !OptoReg::is_valid(_callees[reg]), "oop can't be callee save" );
       // Check for a legal reg name in the oopMap and bailout if it is not.
       if (!omap->legal_vm_reg_name(r)) {
-        regalloc->C->record_method_not_compilable("illegal oopMap register name");
+        stringStream ss;
+        ss.print("illegal oopMap register name: ");
+        r->print_on(&ss);
+        assert(false, "%s", ss.as_string());
+        regalloc->C->record_method_not_compilable(ss.as_string());
         continue;
       }
       if( mcall ) {

src/hotspot/share/opto/compile.cpp

@@ -753,7 +753,11 @@ Compile::Compile( ciEnv* ci_env, ciMethod* target, int osr_bci,
     }
     if (failing())  return;
     if (cg == nullptr) {
-      record_method_not_compilable("cannot parse method");
+      const char* reason = InlineTree::check_can_parse(method());
+      assert(reason != nullptr, "expect reason for parse failure");
+      stringStream ss;
+      ss.print("cannot parse method: %s", reason);
+      record_method_not_compilable(ss.as_string());
       return;
     }
 
@@ -762,7 +766,10 @@ Compile::Compile( ciEnv* ci_env, ciMethod* target, int osr_bci,
     JVMState* jvms = build_start_state(start(), tf());
     if ((jvms = cg->generate(jvms)) == nullptr) {
       if (!failure_reason_is(C2Compiler::retry_class_loading_during_parsing())) {
-        record_method_not_compilable("method parse failed");
+        assert(failure_reason() != nullptr, "expect reason for parse failure");
+        stringStream ss;
+        ss.print("method parse failed: %s", failure_reason());
+        record_method_not_compilable(ss.as_string());
       }
       return;
     }
@@ -3922,6 +3929,8 @@ bool Compile::final_graph_reshaping() {
   // an infinite loop may have been eliminated by the optimizer,
   // in which case the graph will be empty.
   if (root()->req() == 1) {
+    // Do not compile method that is only a trivial infinite loop,
+    // since the content of the loop may have been eliminated.
     record_method_not_compilable("trivial infinite loop");
     return true;
   }
@@ -3987,8 +3996,11 @@ bool Compile::final_graph_reshaping() {
           }
         }
       }
+
       // Recheck with a better notion of 'required_outcnt'
       if (n->outcnt() != required_outcnt) {
+        DEBUG_ONLY( n->dump_bfs(1, 0, "-"); );
+        assert(false, "malformed control flow");
         record_method_not_compilable("malformed control flow");
         return true;            // Not all targets reachable!
       }
@@ -4007,6 +4019,9 @@ bool Compile::final_graph_reshaping() {
     // must be infinite loops.
     for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++)
       if (!frc._visited.test(n->fast_out(j)->_idx)) {
+        DEBUG_ONLY( n->fast_out(j)->dump(); );
+        DEBUG_ONLY( n->dump_bfs(1, 0, "-"); );
+        assert(false, "infinite loop");
         record_method_not_compilable("infinite loop");
         return true;            // Found unvisited kid; must be unreach
       }

src/hotspot/share/opto/domgraph.cpp

@@ -86,6 +86,7 @@ void PhaseCFG::build_dominator_tree() {
     // such dead loops (as was done for the NTarjan code farther below).
     // Since this situation is so unlikely, instead I've decided to bail out.
     // CNC 7/24/2001
+    assert(false, "unreachable loop");
     C->record_method_not_compilable("unreachable loop");
     return;
   }

src/hotspot/share/opto/gcm.cpp

@@ -1500,6 +1500,7 @@ void PhaseCFG::global_code_motion() {
   Node_Stack stack((C->live_nodes() >> 2) + 16); // pre-grow
   if (!schedule_early(visited, stack)) {
     // Bailout without retry
+    assert(false, "early schedule failed");
     C->record_method_not_compilable("early schedule failed");
     return;
   }
@@ -1600,6 +1601,7 @@ void PhaseCFG::global_code_motion() {
     Block* block = get_block(i);
     if (!schedule_local(block, ready_cnt, visited, recalc_pressure_nodes)) {
       if (!C->failure_reason_is(C2Compiler::retry_no_subsuming_loads())) {
+        assert(false, "local schedule failed");
         C->record_method_not_compilable("local schedule failed");
       }
       _regalloc = nullptr;

src/hotspot/share/opto/loopnode.cpp

@@ -4310,6 +4310,7 @@ void PhaseIdealLoop::build_and_optimize() {
   if (!has_node(C->root())) {
     if (!_verify_only) {
       C->clear_major_progress();
+      assert(false, "empty program detected during loop optimization");
       C->record_method_not_compilable("empty program detected during loop optimization");
     }
     return;
@@ -5171,6 +5172,7 @@ int PhaseIdealLoop::build_loop_tree_impl( Node *n, int pre_order ) {
             m->dump();
           }
 #endif
+          // This is a rare case that we do not want to handle in C2.
           C->record_method_not_compilable("unhandled CFG detected during loop optimization");
           return pre_order;
         }

src/hotspot/share/opto/matcher.cpp

@@ -142,6 +142,7 @@ OptoReg::Name Matcher::warp_incoming_stk_arg( VMReg reg ) {
       _in_arg_limit = OptoReg::add(warped, 1); // Bump max stack slot seen
     if (!RegMask::can_represent_arg(warped)) {
       // the compiler cannot represent this method's calling sequence
+      // Bailout. We do not have space to represent all arguments.
       C->record_method_not_compilable("unsupported incoming calling sequence");
       return OptoReg::Bad;
     }
@@ -311,6 +312,7 @@ void Matcher::match( ) {
 
   if (!RegMask::can_represent_arg(OptoReg::add(_out_arg_limit,-1))) {
     // the compiler cannot represent this method's calling sequence
+    // Bailout. We do not have space to represent all arguments.
     C->record_method_not_compilable("must be able to represent all call arguments in reg mask");
   }
 
@@ -358,6 +360,7 @@ void Matcher::match( ) {
     Node* xroot =        xform( C->root(), 1 );
     if (xroot == nullptr) {
       Matcher::soft_match_failure();  // recursive matching process failed
+      assert(false, "instruction match failed");
       C->record_method_not_compilable("instruction match failed");
     } else {
       // During matching shared constants were attached to C->root()
@@ -389,7 +392,15 @@ void Matcher::match( ) {
     }
   }
   if (C->top() == nullptr || C->root() == nullptr) {
-    C->record_method_not_compilable("graph lost"); // %%% cannot happen?
+    // New graph lost. This is due to a compilation failure we encountered earlier.
+    stringStream ss;
+    if (C->failure_reason() != nullptr) {
+      ss.print("graph lost: %s", C->failure_reason());
+    } else {
+      assert(C->failure_reason() != nullptr, "graph lost: reason unknown");
+      ss.print("graph lost: reason unknown");
+    }
+    C->record_method_not_compilable(ss.as_string());
   }
   if (C->failing()) {
     // delete old;
@@ -1242,6 +1253,7 @@ OptoReg::Name Matcher::warp_outgoing_stk_arg( VMReg reg, OptoReg::Name begin_out
     if( warped >= out_arg_limit_per_call )
       out_arg_limit_per_call = OptoReg::add(warped,1);
     if (!RegMask::can_represent_arg(warped)) {
+      // Bailout. For example not enough space on stack for all arguments. Happens for methods with too many arguments.
       C->record_method_not_compilable("unsupported calling sequence");
       return OptoReg::Bad;
     }
@@ -1434,6 +1446,7 @@ MachNode *Matcher::match_sfpt( SafePointNode *sfpt ) {
     uint r_cnt = mcall->tf()->range()->cnt();
     MachProjNode *proj = new MachProjNode( mcall, r_cnt+10000, RegMask::Empty, MachProjNode::fat_proj );
     if (!RegMask::can_represent_arg(OptoReg::Name(out_arg_limit_per_call-1))) {
+      // Bailout. We do not have space to represent all arguments.
       C->record_method_not_compilable("unsupported outgoing calling sequence");
     } else {
       for (int i = begin_out_arg_area; i < out_arg_limit_per_call; i++)
@@ -1621,6 +1634,7 @@ Node* Matcher::Label_Root(const Node* n, State* svec, Node* control, Node*& mem)
   // out of stack space.  See bugs 6272980 & 6227033 for more info.
   LabelRootDepth++;
   if (LabelRootDepth > MaxLabelRootDepth) {
+    // Bailout. Can for example be hit with a deep chain of operations.
     C->record_method_not_compilable("Out of stack space, increase MaxLabelRootDepth");
     return nullptr;
   }

src/hotspot/share/opto/output.cpp

@@ -2849,6 +2849,8 @@ void Scheduling::anti_do_def( Block *b, Node *def, OptoReg::Name def_reg, int is
       pinch = new Node(1); // Pinch point to-be
     }
     if (pinch->_idx >= _regalloc->node_regs_max_index()) {
+      DEBUG_ONLY( pinch->dump(); );
+      assert(false, "too many D-U pinch points: %d >= %d", pinch->_idx, _regalloc->node_regs_max_index());
       _cfg->C->record_method_not_compilable("too many D-U pinch points");
       return;
     }

src/hotspot/share/opto/parse1.cpp

@@ -213,6 +213,7 @@ void Parse::load_interpreter_state(Node* osr_buf) {
   }
   // Do not OSR inside finally clauses:
   if (osr_block->has_trap_at(osr_block->start())) {
+    assert(false, "OSR starts with an immediate trap");
     C->record_method_not_compilable("OSR starts with an immediate trap");
     return;
   }
@@ -253,6 +254,7 @@ void Parse::load_interpreter_state(Node* osr_buf) {
   MethodLivenessResult live_locals = method()->liveness_at_bci(osr_bci());
   if (!live_locals.is_valid()) {
     // Degenerate or breakpointed method.
+    assert(false, "OSR in empty or breakpointed method");
     C->record_method_not_compilable("OSR in empty or breakpointed method");
     return;
   }
@@ -429,6 +431,7 @@ Parse::Parse(JVMState* caller, ciMethod* parse_method, float expected_uses)
   _iter.reset_to_method(method());
   _flow = method()->get_flow_analysis();
   if (_flow->failing()) {
+    assert(false, "type flow failed during parsing");
     C->record_method_not_compilable(_flow->failure_reason());
   }
 
@@ -507,6 +510,7 @@ Parse::Parse(JVMState* caller, ciMethod* parse_method, float expected_uses)
     _entry_bci = C->entry_bci();
     _flow = method()->get_osr_flow_analysis(osr_bci());
     if (_flow->failing()) {
+      assert(false, "type flow analysis failed for OSR compilation");
       C->record_method_not_compilable(_flow->failure_reason());
 #ifndef PRODUCT
       if (PrintOpto && (Verbose || WizardMode)) {
@@ -1044,6 +1048,7 @@ void Parse::do_exits() {
       // loading.  It could also be due to an error, so mark this method as not compilable because
       // otherwise this could lead to an infinite compile loop.
       // In any case, this code path is rarely (and never in my testing) reached.
+      assert(false, "Can't determine return type.");
       C->record_method_not_compilable("Can't determine return type.");
       return;
     }
@@ -1119,6 +1124,7 @@ SafePointNode* Parse::create_entry_map() {
   // Check for really stupid bail-out cases.
   uint len = TypeFunc::Parms + method()->max_locals() + method()->max_stack();
   if (len >= 32760) {
+    // Bailout expected, this is a very rare edge case.
     C->record_method_not_compilable("too many local variables");
     return nullptr;
   }

src/hotspot/share/opto/reg_split.cpp

@@ -306,6 +306,7 @@ Node* clone_node(Node* def, Block *b, Compile* C) {
       C->record_failure(C2Compiler::retry_no_subsuming_loads());
     } else {
       // Bailout without retry
+      assert(false, "RA Split failed: attempt to clone node with anti_dependence");
       C->record_method_not_compilable("RA Split failed: attempt to clone node with anti_dependence");
     }
     return 0;