Inject only relevant local variables in the expression evaluation context
Summary:
In r259902, LLDB started injecting all the locals in every expression
evaluation. This fixed a bunch of issues, but also caused others, mostly
performance regressions on some codebases. The regressions were bad
enough that we added a setting in r274783 to control the behavior and
we have been shipping with the setting off to avoid the perf regressions.
This patch changes the logic injecting the local variables to only inject
the ones present in the expression typed by the user. The approach is
fairly simple and just scans the typed expression for every local name.
Hopefully this gives us the best of both world as it just realizes the
types of the variables really used by the expression.
Landing this requires the 2 other issues I pointed out today to be addressed
but I wanted to gather comments right away.
Original patch by Frédéric Riss!
Reviewers: jingham, clayborg, friss, shafik
Reviewed By: jingham, clayborg
Subscribers: teemperor, labath, lldb-commits
Tags: #lldb
Differential Revision: https://reviews.llvm.org/D46551
llvm-svn: 359773
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionSourceCode.cpp b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionSourceCode.cpp
index 2fc690e..0bc664c 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionSourceCode.cpp
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionSourceCode.cpp
@@ -8,6 +8,9 @@
#include "ClangExpressionSourceCode.h"
+#include "clang/Basic/CharInfo.h"
+#include "llvm/ADT/StringRef.h"
+
#include "Plugins/ExpressionParser/Clang/ClangModulesDeclVendor.h"
#include "Plugins/ExpressionParser/Clang/ClangPersistentVariables.h"
#include "lldb/Symbol/Block.h"
@@ -161,8 +164,43 @@
}
}
+/// Checks if the expression body contains the given variable as a token.
+/// \param body The expression body.
+/// \param var The variable token we are looking for.
+/// \return True iff the expression body containes the variable as a token.
+static bool ExprBodyContainsVar(llvm::StringRef body, llvm::StringRef var) {
+ assert(var.find_if([](char c) { return !clang::isIdentifierBody(c); }) ==
+ llvm::StringRef::npos &&
+ "variable contains non-identifier chars?");
+
+ size_t start = 0;
+ // Iterate over all occurences of the variable string in our expression.
+ while ((start = body.find(var, start)) != llvm::StringRef::npos) {
+ // We found our variable name in the expression. Check that the token
+ // that contains our needle is equal to our variable and not just contains
+ // the character sequence by accident.
+ // Prevents situations where we for example inlcude the variable 'FOO' in an
+ // expression like 'FOObar + 1'.
+ bool has_characters_before =
+ start != 0 && clang::isIdentifierBody(body[start - 1]);
+ bool has_characters_after =
+ start + var.size() < body.size() &&
+ clang::isIdentifierBody(body[start + var.size()]);
+
+ // Our token just contained the variable name as a substring. Continue
+ // searching the rest of the expression.
+ if (has_characters_before || has_characters_after) {
+ ++start;
+ continue;
+ }
+ return true;
+ }
+ return false;
+}
+
static void AddLocalVariableDecls(const lldb::VariableListSP &var_list_sp,
- StreamString &stream) {
+ StreamString &stream,
+ const std::string &expr) {
for (size_t i = 0; i < var_list_sp->GetSize(); i++) {
lldb::VariableSP var_sp = var_list_sp->GetVariableAtIndex(i);
@@ -170,15 +208,17 @@
if (!var_name || var_name == "this" || var_name == ".block_descriptor")
continue;
+ if (!expr.empty() && !ExprBodyContainsVar(expr, var_name.GetStringRef()))
+ continue;
+
stream.Printf("using $__lldb_local_vars::%s;\n", var_name.AsCString());
}
}
-bool ClangExpressionSourceCode::GetText(std::string &text,
- lldb::LanguageType wrapping_language,
- bool static_method,
- ExecutionContext &exe_ctx, bool add_locals,
- llvm::ArrayRef<std::string> modules) const {
+bool ClangExpressionSourceCode::GetText(
+ std::string &text, lldb::LanguageType wrapping_language, bool static_method,
+ ExecutionContext &exe_ctx, bool add_locals, bool force_add_all_locals,
+ llvm::ArrayRef<std::string> modules) const {
const char *target_specific_defines = "typedef signed char BOOL;\n";
std::string module_macros;
@@ -256,7 +296,8 @@
if (target->GetInjectLocalVariables(&exe_ctx)) {
lldb::VariableListSP var_list_sp =
frame->GetInScopeVariableList(false, true);
- AddLocalVariableDecls(var_list_sp, lldb_local_var_decls);
+ AddLocalVariableDecls(var_list_sp, lldb_local_var_decls,
+ force_add_all_locals ? "" : m_body);
}
}
}