r239476 - some StmtExprs do not have side-effects
Scott Douglass
sdouglass at arm.com
Wed Jun 10 08:18:23 PDT 2015
Author: scott-0
Date: Wed Jun 10 10:18:23 2015
New Revision: 239476
URL: http://llvm.org/viewvc/llvm-project?rev=239476&view=rev
Log:
some StmtExprs do not have side-effects
Differential Revision: http://reviews.llvm.org/D10211
Added:
cfe/trunk/test/Sema/stmtexprs.c (with props)
Modified:
cfe/trunk/include/clang/AST/EvaluatedExprVisitor.h
cfe/trunk/lib/AST/Expr.cpp
Modified: cfe/trunk/include/clang/AST/EvaluatedExprVisitor.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/AST/EvaluatedExprVisitor.h?rev=239476&r1=239475&r2=239476&view=diff
==============================================================================
--- cfe/trunk/include/clang/AST/EvaluatedExprVisitor.h (original)
+++ cfe/trunk/include/clang/AST/EvaluatedExprVisitor.h Wed Jun 10 10:18:23 2015
@@ -28,6 +28,7 @@ class ASTContext;
/// of its potentially-evaluated subexpressions, recursively.
template<template <typename> class Ptr, typename ImplClass>
class EvaluatedExprVisitorBase : public StmtVisitorBase<Ptr, ImplClass, void> {
+protected:
const ASTContext &Context;
public:
Modified: cfe/trunk/lib/AST/Expr.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/Expr.cpp?rev=239476&r1=239475&r2=239476&view=diff
==============================================================================
--- cfe/trunk/lib/AST/Expr.cpp (original)
+++ cfe/trunk/lib/AST/Expr.cpp Wed Jun 10 10:18:23 2015
@@ -2887,6 +2887,28 @@ bool Expr::isConstantInitializer(ASTCont
return false;
}
+namespace {
+ /// \brief Look for any side effects within a Stmt.
+ class SideEffectFinder : public ConstEvaluatedExprVisitor<SideEffectFinder> {
+ typedef ConstEvaluatedExprVisitor<SideEffectFinder> Inherited;
+ const bool IncludePossibleEffects;
+ bool HasSideEffects;
+
+ public:
+ explicit SideEffectFinder(const ASTContext &Context, bool IncludePossible)
+ : Inherited(Context),
+ IncludePossibleEffects(IncludePossible), HasSideEffects(false) { }
+
+ bool hasSideEffects() const { return HasSideEffects; }
+
+ void VisitExpr(const Expr *E) {
+ if (!HasSideEffects &&
+ E->HasSideEffects(Context, IncludePossibleEffects))
+ HasSideEffects = true;
+ }
+ };
+}
+
bool Expr::HasSideEffects(const ASTContext &Ctx,
bool IncludePossibleEffects) const {
// In circumstances where we care about definite side effects instead of
@@ -2974,7 +2996,6 @@ bool Expr::HasSideEffects(const ASTConte
case CompoundAssignOperatorClass:
case VAArgExprClass:
case AtomicExprClass:
- case StmtExprClass:
case CXXThrowExprClass:
case CXXNewExprClass:
case CXXDeleteExprClass:
@@ -2982,6 +3003,13 @@ bool Expr::HasSideEffects(const ASTConte
// These always have a side-effect.
return true;
+ case StmtExprClass: {
+ // StmtExprs have a side-effect if any substatement does.
+ SideEffectFinder Finder(Ctx, IncludePossibleEffects);
+ Finder.Visit(cast<StmtExpr>(this)->getSubStmt());
+ return Finder.hasSideEffects();
+ }
+
case ParenExprClass:
case ArraySubscriptExprClass:
case MemberExprClass:
Added: cfe/trunk/test/Sema/stmtexprs.c
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/stmtexprs.c?rev=239476&view=auto
==============================================================================
--- cfe/trunk/test/Sema/stmtexprs.c (added)
+++ cfe/trunk/test/Sema/stmtexprs.c Wed Jun 10 10:18:23 2015
@@ -0,0 +1,9 @@
+// RUN: %clang_cc1 %s -verify -pedantic -fsyntax-only -Wno-gnu-statement-expression
+
+int stmtexpr_fn();
+void stmtexprs(int i) {
+ __builtin_assume( ({ 1; }) ); // no warning about "side effects"
+ __builtin_assume( ({ if (i) { (void)0; }; 42; }) ); // no warning about "side effects"
+ // expected-warning at +1 {{the argument to '__builtin_assume' has side effects that will be discarded}}
+ __builtin_assume( ({ if (i) ({ stmtexpr_fn(); }); 1; }) );
+}
Propchange: cfe/trunk/test/Sema/stmtexprs.c
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Propchange: cfe/trunk/test/Sema/stmtexprs.c
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svn:keywords = Rev Date Author URL Id
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