tensor,codegen: fix a bug where kernel cache could be modified

include/taco/codegen/module.h

@@ -21,8 +21,6 @@ class Module {
     setJITTmpdir();
   }
 
-  void reset();
-
   /// Compile the source into a library, returning its full path
   std::string compile();
 

src/codegen/module.cpp

@@ -32,15 +32,6 @@ void Module::setJITLibname() {
     libname[i] = chars[rand() % chars.length()];
 }
 
-void Module::reset() {
-  funcs.clear();
-  moduleFromUserSource = false;
-  header.str("");
-  header.clear();
-  source.str("");
-  source.clear();
-}
-
 void Module::addFunction(Stmt func) {
   funcs.push_back(func);
 }

src/tensor.cpp

@@ -595,7 +595,10 @@ void TensorBase::compile(taco::IndexStmt stmt, bool assembleWhileCompute) {
 
   content->assembleFunc = lower(stmtToCompile, "assemble", true, false);
   content->computeFunc = lower(stmtToCompile, "compute",  assembleWhileCompute, true);
-  content->module->reset();
+  // If we have to recompile the kernel, we need to create a new Module. Since
+  // the module we are holding on to could have been retrieved from the cache,
+  // we can't modify it.
+  content->module = make_shared<Module>();
   content->module->addFunction(content->assembleFunc);
   content->module->addFunction(content->computeFunc);
   content->module->compile();

test/tests-tensor.cpp

@@ -479,3 +479,18 @@ TEST(tensor, recompile) {
   ASSERT_TRUE(c.needsCompile());
   ASSERT_EQ(c.begin()->second, 42.0);
 }
+
+TEST(tensor, cache) {
+  auto dim = 2;
+  IndexVar i("i"), j("j");
+  Tensor<int> a("a", {dim, dim}, {Dense, Dense});
+  Tensor<int> b("b", {dim, dim}, {Dense, Dense});
+  Tensor<int> c("c", {dim, dim}, {Dense, Dense});
+  // Add a computation to the cache.
+  c(i, j) = a(i, j); c.evaluate();
+  // Add a new computation to the cache.
+  c(i, j) = a(i, j) + b(i, j); c.evaluate();
+  // The addition of the new computation shouldn't have affected the cache's
+  // ability to answer a request for the first query.
+  c(i, j) = a(i, j); c.evaluate();
+}