-Wunreachable-code: refine recognition of unreachable "sigil" to cope…

… with implicit casts in C++.

Fixes <rdar://problem/16631033>.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@206360 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/AST/Expr.h

@@ -699,6 +699,9 @@ class Expr : public Stmt {
   /// or CastExprs, returning their operand.
   Expr *IgnoreParenCasts() LLVM_READONLY;
 
+  /// Ignore casts.  Strip off any CastExprs, returning their operand.
+  Expr *IgnoreCasts() LLVM_READONLY;
+
   /// IgnoreParenImpCasts - Ignore parentheses and implicit casts.  Strip off
   /// any ParenExpr or ImplicitCastExprs, returning their operand.
   Expr *IgnoreParenImpCasts() LLVM_READONLY;
@@ -760,6 +763,11 @@ class Expr : public Stmt {
   const Expr *IgnoreParenCasts() const LLVM_READONLY {
     return const_cast<Expr*>(this)->IgnoreParenCasts();
   }
+  /// Strip off casts, but keep parentheses.
+  const Expr *IgnoreCasts() const LLVM_READONLY {
+    return const_cast<Expr*>(this)->IgnoreCasts();
+  }
+
   const Expr *IgnoreParenNoopCasts(ASTContext &Ctx) const LLVM_READONLY {
     return const_cast<Expr*>(this)->IgnoreParenNoopCasts(Ctx);
   }

lib/AST/Expr.cpp

@@ -2400,6 +2400,27 @@ Expr *Expr::IgnoreParenCasts() {
   }
 }
 
+Expr *Expr::IgnoreCasts() {
+  Expr *E = this;
+  while (true) {
+    if (CastExpr *P = dyn_cast<CastExpr>(E)) {
+      E = P->getSubExpr();
+      continue;
+    }
+    if (MaterializeTemporaryExpr *Materialize
+        = dyn_cast<MaterializeTemporaryExpr>(E)) {
+      E = Materialize->GetTemporaryExpr();
+      continue;
+    }
+    if (SubstNonTypeTemplateParmExpr *NTTP
+        = dyn_cast<SubstNonTypeTemplateParmExpr>(E)) {
+      E = NTTP->getReplacement();
+      continue;
+    }
+    return E;
+  }
+}
+
 /// IgnoreParenLValueCasts - Ignore parentheses and lvalue-to-rvalue
 /// casts.  This is intended purely as a temporary workaround for code
 /// that hasn't yet been rewritten to do the right thing about those

lib/Analysis/ReachableCode.cpp

@@ -139,14 +139,17 @@ static bool isConfigurationValue(const Stmt *S,
   if (!S)
     return false;
 
+  if (const Expr *Ex = dyn_cast<Expr>(S))
+    S = Ex->IgnoreCasts();
+
   // Special case looking for the sigil '()' around an integer literal.
   if (const ParenExpr *PE = dyn_cast<ParenExpr>(S))
     if (!PE->getLocStart().isMacroID())
       return isConfigurationValue(PE->getSubExpr(), PP, SilenceableCondVal, 
                                   IncludeIntegers, true);
 
   if (const Expr *Ex = dyn_cast<Expr>(S))
-    S = Ex->IgnoreParenCasts();
+    S = Ex->IgnoreCasts();
 
   bool IgnoreYES_NO = false;
 

test/SemaCXX/warn-unreachable.cpp

@@ -327,6 +327,36 @@ void test_with_paren_silencing(int x) {
     calledFun();
 }
 
+void test_with_paren_silencing_impcast(int x) {
+  if (0) calledFun(); // expected-warning {{will never be executed}} expected-note {{silence by adding parentheses to mark code as explicitly dead}}
+  if ((0)) calledFun(); // no-warning
+
+  if (1) // expected-note {{silence by adding parentheses to mark code as explicitly dead}}
+    calledFun();
+  else
+    calledFun(); // expected-warning {{will never be executed}}
+
+  if ((1))
+    calledFun();
+  else
+    calledFun(); // no-warning
+
+  if (!1) // expected-note {{silence by adding parentheses to mark code as explicitly dead}}
+    calledFun(); // expected-warning {{code will never be executed}}
+  else
+    calledFun();
+
+  if ((!1))
+    calledFun(); // no-warning
+  else
+    calledFun();
+
+  if (!(1))
+    calledFun(); // no-warning
+  else
+    calledFun();
+}
+
 void tautological_compare(bool x, int y) {
   if (x > 10)           // expected-note {{silence}}
     calledFun();        // expected-warning {{will never be executed}}