Remove a kludge from analysis based warnings that used to detect

temporaries with no-return destructors. The CFG now properly supports
temporaries and implicit destructors which both makes this kludge no
longer work, and conveniently removes the need for it.

Turn on CFG handling of implicit destructors and initializers. Several
ad-hoc benchmarks don't indicate any measurable performance impact from
growing the CFG, and it fixes real correctness problems with warnings.

As a result of turning on these CFG elements, we started to tickle an
inf-loop in the unreachable code logic used for warnings. The fix is
trivial.

llvm-svn: 123056

clang/lib/Analysis/ReachableCode.cpp

@@ -30,12 +30,11 @@ static SourceLocation GetUnreachableLoc(const CFGBlock &b, SourceRange &R1,
   unsigned sn = 0;
   R1 = R2 = SourceRange();
 
-top:
   if (sn < b.size()) {
     CFGStmt CS = b[sn].getAs<CFGStmt>();
     if (!CS)
-      goto top;
-    
+      return SourceLocation();
+
     S = CS.getStmt(); 
   } else if (b.getTerminator())
     S = b.getTerminator();

clang/lib/Sema/AnalysisBasedWarnings.cpp

@@ -177,19 +177,6 @@ static ControlFlowKind CheckFallThrough(AnalysisContext &AC) {
         }
       }
     }
-    // FIXME: Remove this hack once temporaries and their destructors are
-    // modeled correctly by the CFG.
-    if (ExprWithCleanups *E = dyn_cast<ExprWithCleanups>(S)) {
-      for (unsigned I = 0, N = E->getNumTemporaries(); I != N; ++I) {
-        const FunctionDecl *FD = E->getTemporary(I)->getDestructor();
-        if (FD->hasAttr<NoReturnAttr>() ||
-            FD->getType()->getAs<FunctionType>()->getNoReturnAttr()) {
-          NoReturnEdge = true;
-          HasFakeEdge = true;
-          break;
-        }
-      }
-    }
     // FIXME: Add noreturn message sends.
     if (NoReturnEdge == false)
       HasPlainEdge = true;
@@ -405,7 +392,8 @@ AnalysisBasedWarnings::IssueWarnings(sema::AnalysisBasedWarnings::Policy P,
 
   // Don't generate EH edges for CallExprs as we'd like to avoid the n^2
   // explosion for destrutors that can result and the compile time hit.
-  AnalysisContext AC(D, 0, false);
+  AnalysisContext AC(D, 0, /*useUnoptimizedCFG=*/false, /*addehedges=*/false,
+                     /*addImplicitDtors=*/true, /*addInitializers=*/true);
 
   // Warning: check missing 'return'
   if (P.enableCheckFallThrough) {

clang/test/SemaCXX/return-noreturn.cpp

@@ -7,14 +7,11 @@ namespace PR6884 {
     ~abort_struct() __attribute__((noreturn));
   };
 
-  // FIXME: Should either of these actually warn, since the destructor is
-  //  marked noreturn?
-
   int f() {
     abort_struct();
-  } // expected-warning{{control reaches end of non-void function}}
+  }
 
   int f2() {
     abort_struct s;
-  } // expected-warning{{control reaches end of non-void function}}
+  }
 }