Optimize exception frames allocation

* Make llvm-gcroot a ModulePass
* Use llvm-gcroot to calculate the minimum number of exception frames necessary.

src/codegen.cpp

@@ -381,6 +381,7 @@ static Function *gcroot_func;
 static Function *gckill_func;
 static Function *jlcall_frame_func;
 static Function *gcroot_flush_func;
+static Function *except_enter_func;
 
 static std::vector<Type *> two_pvalue_llvmt;
 static std::vector<Type *> three_pvalue_llvmt;
@@ -505,7 +506,6 @@ typedef struct {
  std::vector<bool> ssavalue_assigned;
  std::map<int, jl_arrayvar_t> *arrayvars;
  std::map<int, BasicBlock*> *labels;
- std::map<int, Value*> *handlers;
  jl_module_t *module;
  jl_lambda_info_t *linfo;
  const char *name;
@@ -3259,18 +3259,7 @@ static jl_cgval_t emit_expr(jl_value_t *expr, jl_codectx_t *ctx)
  else if (head == enter_sym) {
  assert(jl_is_long(args[0]));
  int labl = jl_unbox_long(args[0]);
- Value *jbuf = builder.CreateGEP((*ctx->handlers)[labl],
- ConstantInt::get(T_size,0));
- builder.CreateCall(prepare_call(jlenter_func), jbuf);
-#ifndef _OS_WINDOWS_
-#ifdef LLVM37
- CallInst *sj = builder.CreateCall(prepare_call(setjmp_func), { jbuf, ConstantInt::get(T_int32,0) });
-#else
- CallInst *sj = builder.CreateCall2(prepare_call(setjmp_func), jbuf, ConstantInt::get(T_int32,0));
-#endif
-#else
- CallInst *sj = builder.CreateCall(prepare_call(setjmp_func), jbuf);
-#endif
+ CallInst *sj = builder.CreateCall(prepare_call(except_enter_func));
  // We need to mark this on the call site as well. See issue #6757
  sj->setCanReturnTwice();
  Value *isz = builder.CreateICmpEQ(sj, ConstantInt::get(T_int32,0));
@@ -3892,11 +3881,9 @@ static std::unique_ptr<Module> emit_function(jl_lambda_info_t *lam, jl_llvm_func
  //jl_printf(JL_STDOUT, "\n");
  std::map<int, jl_arrayvar_t> arrayvars;
  std::map<int, BasicBlock*> labels;
- std::map<int, Value*> handlers;
  jl_codectx_t ctx = {};
  ctx.arrayvars = &arrayvars;
  ctx.labels = &labels;
- ctx.handlers = &handlers;
  ctx.module = lam->def ? lam->def->module : ptls->current_module;
  ctx.linfo = lam;
  ctx.name = jl_symbol_name(lam->def ? lam->def->name : anonymous_sym);
@@ -4329,18 +4316,6 @@ static std::unique_ptr<Module> emit_function(jl_lambda_info_t *lam, jl_llvm_func
  allocate_gc_frame(b0, &ctx);
 
  // step 8. allocate space for exception handler contexts
- for(i=0; i < stmtslen; i++) {
- jl_value_t *stmt = jl_array_ptr_ref(stmts,i);
- if (jl_is_expr(stmt) && ((jl_expr_t*)stmt)->head == enter_sym) {
- int labl = jl_unbox_long(jl_exprarg(stmt,0));
- AllocaInst *handlr =
- builder.CreateAlloca(T_int8,
- ConstantInt::get(T_int32,
- sizeof(jl_handler_t)));
- handlr->setAlignment(16);
- handlers[labl] = handlr;
- }
- }
 
  // step 9. allocate local variables slots
  // must be in the first basic block for the llvm mem2reg pass to work
@@ -5533,6 +5508,12 @@ static void init_julia_llvm_env(Module *m)
  "julia.gcroot_flush", m);
  add_named_global(gcroot_flush_func, (void*)NULL, /*dllimport*/false);
 
+ except_enter_func = Function::Create(FunctionType::get(T_int32, false),
+ Function::ExternalLinkage,
+ "julia.except_enter", m);
+ except_enter_func->addFnAttr(Attribute::ReturnsTwice);
+ add_named_global(except_enter_func, (void*)NULL, /*dllimport*/false);
+
  // set up optimization passes
 #ifdef LLVM37
 // No DataLayout pass needed anymore.