[LifetimeSafety] Add language option for experimental lifetime safety (llvm#149592)

Add a language option flag for experimental lifetime safety analysis in C++.

This change provides a language option to control the experimental lifetime safety analysis feature, making it more explicit and easier to enable/disable. Previously, the feature was controlled indirectly through a diagnostic warning flag, which we do not want to accidentally enable with `-Weverything` (atm)!

- Added a new language option `EnableLifetimeSafety` in `LangOptions.def` for experimental lifetime safety analysis in C++
- Added corresponding driver options `-fexperimental-lifetime-safety` and `-fno-experimental-lifetime-safety` in `Options.td`
- Modified `AnalysisBasedWarnings.cpp` to use the new language option flag instead of checking if a specific diagnostic is ignored
- Updated a test case to use the new flag instead of relying on the warning flag alone

Author: usx95

clang/include/clang/Basic/LangOptions.def

@@ -506,6 +506,8 @@ LANGOPT(CheckConstexprFunctionBodies, 1, 1, Benign,
 
 LANGOPT(BoundsSafety, 1, 0, NotCompatible, "Bounds safety extension for C")
 
+LANGOPT(EnableLifetimeSafety, 1, 0, NotCompatible, "Experimental lifetime safety analysis for C++")
+
 LANGOPT(PreserveVec3Type, 1, 0, NotCompatible, "Preserve 3-component vector type")
 
 #undef LANGOPT

clang/include/clang/Driver/Options.td

@@ -1913,6 +1913,14 @@ defm bounds_safety : BoolFOption<
   BothFlags<[], [CC1Option],
           " experimental bounds safety extension for C">>;
 
+defm lifetime_safety : BoolFOption<
+  "experimental-lifetime-safety",
+  LangOpts<"EnableLifetimeSafety">, DefaultFalse,
+  PosFlag<SetTrue, [], [CC1Option], "Enable">,
+  NegFlag<SetFalse, [], [CC1Option], "Disable">,
+  BothFlags<[], [CC1Option],
+          " experimental lifetime safety for C++">>;
+
 defm addrsig : BoolFOption<"addrsig",
   CodeGenOpts<"Addrsig">, DefaultFalse,
   PosFlag<SetTrue, [], [ClangOption, CC1Option], "Emit">,

clang/lib/Sema/AnalysisBasedWarnings.cpp

@@ -2890,8 +2890,7 @@ void clang::sema::AnalysisBasedWarnings::IssueWarnings(
       .setAlwaysAdd(Stmt::UnaryOperatorClass);
   }
 
-  bool EnableLifetimeSafetyAnalysis = !Diags.isIgnored(
-      diag::warn_experimental_lifetime_safety_dummy_warning, D->getBeginLoc());
+  bool EnableLifetimeSafetyAnalysis = S.getLangOpts().EnableLifetimeSafety;
   // Install the logical handler.
   std::optional<LogicalErrorHandler> LEH;
   if (LogicalErrorHandler::hasActiveDiagnostics(Diags, D->getBeginLoc())) {

clang/test/Sema/warn-lifetime-safety-dataflow.cpp

@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -mllvm -debug-only=LifetimeFacts,LifetimeLoanPropagation -Wexperimental-lifetime-safety %s 2>&1 | FileCheck %s
+// RUN: %clang_cc1 -fexperimental-lifetime-safety -mllvm -debug-only=LifetimeFacts -Wexperimental-lifetime-safety %s 2>&1 | FileCheck %s
 // REQUIRES: asserts
 
 struct MyObj {
@@ -19,10 +19,6 @@ MyObj* return_local_addr() {
 // CHECK:   ReturnOfOrigin (OriginID: [[O_RET_VAL]])
 // CHECK:   Expire (LoanID: [[L_X]])
 }
-// CHECK: LoanPropagation results:
-// CHECK-DAG: Origin [[O_ADDR_X]] contains Loan [[L_X]]
-// CHECK-DAG: Origin [[O_P]] contains Loan [[L_X]]
-// CHECK-DAG: Origin [[O_RET_VAL]] contains Loan [[L_X]]
 
 
 // Pointer Assignment and Return
@@ -47,15 +43,6 @@ MyObj* assign_and_return_local_addr() {
 // CHECK: ReturnOfOrigin (OriginID: [[O_PTR2_RVAL_2]])
 // CHECK: Expire (LoanID: [[L_Y]])
 }
-// CHECK: LoanPropagation results:
-// CHECK-DAG: Origin [[O_ADDR_Y]] contains Loan [[L_Y]]
-// CHECK-DAG: Origin [[O_PTR1]] contains Loan [[L_Y]]
-// CHECK-DAG: Origin [[O_PTR2]] contains Loan [[L_Y]]
-// CHECK-DAG: Origin [[O_PTR1_RVAL]] contains Loan [[L_Y]]
-// CHECK-DAG: Origin [[O_PTR1_RVAL_2]] contains Loan [[L_Y]]
-// CHECK-DAG: Origin [[O_PTR2_RVAL]] contains Loan [[L_Y]]
-// CHECK-DAG: Origin [[O_PTR2_RVAL_2]] contains Loan [[L_Y]]
-
 
 // Return of Non-Pointer Type
 // CHECK-LABEL: Function: return_int_val
@@ -65,8 +52,6 @@ int return_int_val() {
   return x;
 }
 // CHECK-NEXT: End of Block
-// CHECK: LoanPropagation results:
-// CHECK:  <empty>
 
 
 // Loan Expiration (Automatic Variable, C++)
@@ -79,9 +64,6 @@ void loan_expires_cpp() {
 // CHECK: AssignOrigin (DestID: [[O_POBJ:[0-9]+]], SrcID: [[O_ADDR_OBJ]])
 // CHECK: Expire (LoanID: [[L_OBJ]])
 }
-// CHECK: LoanPropagation results:
-// CHECK-DAG: Origin [[O_ADDR_OBJ]] contains Loan [[L_OBJ]]
-// CHECK-DAG: Origin [[O_POBJ]] contains Loan [[L_OBJ]]
 
 
 // FIXME: No expire for Trivial Destructors
@@ -96,10 +78,6 @@ void loan_expires_trivial() {
 // CHECK-NEXT: End of Block
   // FIXME: Add check for Expire once trivial destructors are handled for expiration.
 }
-// CHECK: LoanPropagation results:
-// CHECK-DAG: Origin [[O_ADDR_TRIVIAL_OBJ]] contains Loan [[L_TRIVIAL_OBJ]]
-// CHECK-DAG: Origin [[O_PTOBJ]] contains Loan [[L_TRIVIAL_OBJ]]
-
 
 // CHECK-LABEL: Function: conditional
 void conditional(bool condition) {
@@ -119,13 +97,6 @@ void conditional(bool condition) {
   // CHECK: AssignOrigin (DestID: [[O_P_RVAL:[0-9]+]], SrcID: [[O_P]])
   // CHECK: AssignOrigin (DestID: [[O_Q:[0-9]+]], SrcID: [[O_P_RVAL]])
 }
-// CHECK: LoanPropagation results:
-// CHECK-DAG: Origin [[O_ADDR_A]] contains Loan [[L_A]]
-// CHECK-DAG: Origin [[O_ADDR_B]] contains Loan [[L_B]]
-// CHECK-DAG: Origin [[O_P]] contains Loan [[L_A]]
-// CHECK-DAG: Origin [[O_P]] contains Loan [[L_B]]
-// CHECK-DAG: Origin [[O_Q]] contains Loan [[L_A]]
-// CHECK-DAG: Origin [[O_Q]] contains Loan [[L_B]]
 
 
 // CHECK-LABEL: Function: pointers_in_a_cycle
@@ -161,25 +132,6 @@ void pointers_in_a_cycle(bool condition) {
 // CHECK:   AssignOrigin (DestID: [[O_P3]], SrcID: [[O_TEMP_RVAL]])
   }
 }
-// At the end of the analysis, the origins for the pointers involved in the cycle
-// (p1, p2, p3, temp) should all contain the loans from v1, v2, and v3 at the fixed point.
-// CHECK: LoanPropagation results:
-// CHECK-DAG: Origin [[O_P1]] contains Loan [[L_V1]]
-// CHECK-DAG: Origin [[O_P1]] contains Loan [[L_V2]]
-// CHECK-DAG: Origin [[O_P1]] contains Loan [[L_V3]]
-// CHECK-DAG: Origin [[O_P2]] contains Loan [[L_V1]]
-// CHECK-DAG: Origin [[O_P2]] contains Loan [[L_V2]]
-// CHECK-DAG: Origin [[O_P2]] contains Loan [[L_V3]]
-// CHECK-DAG: Origin [[O_P3]] contains Loan [[L_V1]]
-// CHECK-DAG: Origin [[O_P3]] contains Loan [[L_V2]]
-// CHECK-DAG: Origin [[O_P3]] contains Loan [[L_V3]]
-// CHECK-DAG: Origin [[O_TEMP]] contains Loan [[L_V1]]
-// CHECK-DAG: Origin [[O_TEMP]] contains Loan [[L_V2]]
-// CHECK-DAG: Origin [[O_TEMP]] contains Loan [[L_V3]]
-// CHECK-DAG: Origin [[O_ADDR_V1]] contains Loan [[L_V1]]
-// CHECK-DAG: Origin [[O_ADDR_V2]] contains Loan [[L_V2]]
-// CHECK-DAG: Origin [[O_ADDR_V3]] contains Loan [[L_V3]]
-
 
 // CHECK-LABEL: Function: overwrite_origin
 void overwrite_origin() {
@@ -195,10 +147,6 @@ void overwrite_origin() {
 // CHECK:   Expire (LoanID: [[L_S2]])
 // CHECK:   Expire (LoanID: [[L_S1]])
 }
-// CHECK: LoanPropagation results:
-// CHECK:     Origin [[O_P]] contains Loan [[L_S2]]
-// CHECK-NOT: Origin [[O_P]] contains Loan [[L_S1]]
-
 
 // CHECK-LABEL: Function: reassign_to_null
 void reassign_to_null() {
@@ -213,8 +161,6 @@ void reassign_to_null() {
 }
 // FIXME: Have a better representation for nullptr than just an empty origin. 
 //        It should be a separate loan and origin kind.
-// CHECK: LoanPropagation results:
-// CHECK: Origin [[O_P]] contains no loans
 
 
 // CHECK-LABEL: Function: reassign_in_if
@@ -235,11 +181,6 @@ void reassign_in_if(bool condition) {
 // CHECK:   Expire (LoanID: [[L_S2]])
 // CHECK:   Expire (LoanID: [[L_S1]])
 }
-// CHECK: LoanPropagation results:
-// CHECK-DAG: Origin [[O_P]] contains Loan [[L_S1]]
-// CHECK-DAG: Origin [[O_P]] contains Loan [[L_S2]]
-// CHECK-DAG: Origin [[O_ADDR_S1]] contains Loan [[L_S1]]
-// CHECK-DAG: Origin [[O_ADDR_S2]] contains Loan [[L_S2]]
 
 
 // CHECK-LABEL: Function: assign_in_switch
@@ -276,14 +217,6 @@ void assign_in_switch(int mode) {
 // CHECK-DAG:   Expire (LoanID: [[L_S2]])
 // CHECK-DAG:   Expire (LoanID: [[L_S1]])
 }
-// CHECK: LoanPropagation results:
-// CHECK-DAG: Origin [[O_P]] contains Loan [[L_S1]]
-// CHECK-DAG: Origin [[O_P]] contains Loan [[L_S2]]
-// CHECK-DAG: Origin [[O_P]] contains Loan [[L_S3]]
-// CHECK-DAG: Origin [[O_ADDR_S1]] contains Loan [[L_S1]]
-// CHECK-DAG: Origin [[O_ADDR_S2]] contains Loan [[L_S2]]
-// CHECK-DAG: Origin [[O_ADDR_S3]] contains Loan [[L_S3]]
-
 
 // CHECK-LABEL: Function: loan_in_loop
 void loan_in_loop(bool condition) {
@@ -299,10 +232,6 @@ void loan_in_loop(bool condition) {
 // CHECK:   Expire (LoanID: [[L_INNER]])
   }
 }
-// CHECK: LoanPropagation results:
-// CHECK-DAG: Origin [[O_P]] contains Loan [[L_INNER]]
-// CHECK-DAG: Origin [[O_ADDR_INNER]] contains Loan [[L_INNER]]
-
 
 // CHECK-LABEL: Function: loop_with_break
 void loop_with_break(int count) {
@@ -326,13 +255,6 @@ void loop_with_break(int count) {
 // CHECK:   Expire (LoanID: [[L_S1]])
 }
 
-// CHECK-LABEL: LoanPropagation results:
-// CHECK-DAG: Origin [[O_P]] contains Loan [[L_S1]]
-// CHECK-DAG: Origin [[O_P]] contains Loan [[L_S2]]
-// CHECK-DAG: Origin [[O_ADDR_S1]] contains Loan [[L_S1]]
-// CHECK-DAG: Origin [[O_ADDR_S2]] contains Loan [[L_S2]]
-
-
 // CHECK-LABEL: Function: nested_scopes
 void nested_scopes() {
   MyObj* p = nullptr;
@@ -355,13 +277,6 @@ void nested_scopes() {
 // CHECK:   Expire (LoanID: [[L_OUTER]])
 }
 
-// CHECK-LABEL: LoanPropagation results:
-// CHECK-DAG: Origin [[O_P]] contains Loan [[L_INNER]]
-// CHECK-DAG: Origin [[O_ADDR_INNER]] contains Loan [[L_INNER]]
-// CHECK-DAG: Origin [[O_ADDR_OUTER]] contains Loan [[L_OUTER]]
-// CHECK-NOT: Origin [[O_P]] contains Loan [[L_OUTER]]
-
-
 // CHECK-LABEL: Function: pointer_indirection
 void pointer_indirection() {
   int a;