[CodeGen] avoid crash if an exception is raised during llvm cpu codeg…

…en (apache#9786)

* avoid crash if an exception is raised during llvm cpu codegen

* use pytest.raises

src/target/llvm/codegen_cpu.cc

@@ -492,6 +492,28 @@ llvm::BasicBlock* CodeGenCPU::CheckCallSuccess(llvm::Value* retcode) {
 }
 
 void CodeGenCPU::CreateComputeScope(const AttrStmtNode* op) {
+  /*! \brief maintain states that should be guarded when step into compute scope */
+  struct ComputeScopeStates {
+    explicit ComputeScopeStates(CodeGenCPU* parent) : parent_(parent) {}
+
+    void EnterWithScope() {
+      std::swap(function_, parent_->function_);
+      std::swap(analyzer_, parent_->analyzer_);
+      std::swap(var_map_, parent_->var_map_);
+    }
+
+    void ExitWithScope() {
+      std::swap(function_, parent_->function_);
+      std::swap(analyzer_, parent_->analyzer_);
+      std::swap(var_map_, parent_->var_map_);
+    }
+
+    llvm::Function* function_{nullptr};
+    std::unordered_map<const VarNode*, llvm::Value*> var_map_;
+    std::unique_ptr<arith::Analyzer> analyzer_{std::make_unique<arith::Analyzer>()};
+    CodeGenCPU* parent_;
+  };
+
   // There are two reasons why we create another function for compute_scope
   // - Make sure the generated compute function is clearly separately(though it can get inlined)
   // - Set noalias on all the pointer arguments, some of them are loaded from TVMArgs.
@@ -515,13 +537,13 @@ void CodeGenCPU::CreateComputeScope(const AttrStmtNode* op) {
       llvm::Function::Create(ftype, llvm::Function::InternalLinkage,
                              value->value.operator llvm::StringRef(), module_.get());
   BasicBlock* compute_call_end = CheckCallSuccess(builder_->CreateCall(fcompute, arg_values));
-  // setup compute function.
-  std::unordered_map<const VarNode*, llvm::Value*> new_vmap;
+  // enter compute scope and setup compute function.
+  With<ComputeScopeStates> scope_states_guard(this);
   size_t idx = 0;
   for (auto it = fcompute->arg_begin(); it != fcompute->arg_end(); ++it, ++idx) {
     llvm::Argument* v = &(*it);
     const Var& var = vargs[idx];
-    new_vmap[var.get()] = v;
+    var_map_[var.get()] = v;
     if (var.dtype().is_handle() && !alias_var_set_.count(var.get())) {
       // set non alias.
 #if TVM_LLVM_VERSION >= 50
@@ -544,18 +566,11 @@ void CodeGenCPU::CreateComputeScope(const AttrStmtNode* op) {
     }
 #endif
   }
-  auto new_analyzer = std::make_unique<arith::Analyzer>();
-  std::swap(function_, fcompute);
-  std::swap(analyzer_, new_analyzer);
-  std::swap(var_map_, new_vmap);
+  function_ = fcompute;
   BasicBlock* compute_entry = BasicBlock::Create(*ctx_, "entry", function_);
   builder_->SetInsertPoint(compute_entry);
   this->VisitStmt(op->body);
   builder_->CreateRet(ConstInt32(0));
-  // swap the var map back, now we are back on track.
-  std::swap(var_map_, new_vmap);
-  std::swap(analyzer_, new_analyzer);
-  std::swap(function_, fcompute);
   builder_->SetInsertPoint(compute_call_end);
 }
 

tests/python/unittest/test_target_codegen_llvm.py

@@ -24,6 +24,7 @@
 from tvm import te
 from tvm.relay.backend import Runtime
 from tvm.contrib import utils, clang
+import tvm.script.tir as T
 import numpy as np
 
 import math
@@ -906,5 +907,22 @@ def test_llvm_scalar_concat():
         m = tvm.build(mod, [x, y, z], target="llvm")
 
 
+@tvm.testing.requires_llvm
+def test_raise_exception_during_codegen():
+    @T.prim_func
+    def threadpool_nested_parallel_loop(
+        A: T.Buffer[(4, 4), "float32"], B: T.Buffer[(4, 4), "float32"]
+    ) -> None:
+        T.func_attr({"global_symbol": "main", "tir.noalias": True})
+        for i in T.parallel(4):
+            for j in T.parallel(4):
+                T.store(B.data, i * 4 + j, T.load("float32", A.data, i * 4 + j) * 2.0)
+
+    with pytest.raises(tvm.TVMError) as e:
+        tvm.build({"llvm": tvm.IRModule.from_expr(threadpool_nested_parallel_loop)})
+    msg = str(e)
+    assert msg.find("Nested parallel loop is not supported") != -1
+
+
 if __name__ == "__main__":
     sys.exit(pytest.main([__file__] + sys.argv[1:]))