[cfe-commits] r109314 - in /cfe/trunk: lib/Sema/SemaExpr.cpp test/CodeGenCXX/static-init-2.cpp test/Sema/exprs.c test/Sema/switch.c test/SemaCXX/switch.cpp

[Chris Lattner]

Author: lattner
Date: Fri Jul 23 20:10:11 2010
New Revision: 109314

URL: http://llvm.org/viewvc/llvm-project?rev=109314&view=rev
Log:
turn down the logical bitwise confusion warning to not warn 
when the RHS of the ||/&& is ever 0 or 1.  This handles a variety of
creative idioms for "true" used in C programs and fixes many false 
positives at the expense of a few false negatives.  This fixes
rdar://8230351.


Modified:
    cfe/trunk/lib/Sema/SemaExpr.cpp
    cfe/trunk/test/CodeGenCXX/static-init-2.cpp
    cfe/trunk/test/Sema/exprs.c
    cfe/trunk/test/Sema/switch.c
    cfe/trunk/test/SemaCXX/switch.cpp

Modified: cfe/trunk/lib/Sema/SemaExpr.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaExpr.cpp?rev=109314&r1=109313&r2=109314&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaExpr.cpp (original)
+++ cfe/trunk/lib/Sema/SemaExpr.cpp Fri Jul 23 20:10:11 2010
@@ -5819,18 +5819,21 @@
   // bitwise one.  We do this when the LHS is a non-bool integer and the RHS
   // is a constant.
   if (lex->getType()->isIntegerType() && !lex->getType()->isBooleanType() &&
-      rex->getType()->isIntegerType() && rex->isEvaluatable(Context) &&
-      // Don't warn if the RHS is a (constant folded) boolean expression like
-      // "sizeof(int) == 4".
-      !rex->isKnownToHaveBooleanValue() &&
+      rex->getType()->isIntegerType() &&
       // Don't warn in macros.
-      !Loc.isMacroID())
-    Diag(Loc, diag::warn_logical_instead_of_bitwise)
-     << rex->getSourceRange()
-      << (Opc == BinaryOperator::LAnd ? "&&" : "||")
-      << (Opc == BinaryOperator::LAnd ? "&" : "|");
-  
-  
+      !Loc.isMacroID()) {
+    // If the RHS can be constant folded, and if it constant folds to something
+    // that isn't 0 or 1 (which indicate a potential logical operation that
+    // happened to fold to true/false) then warn.
+    Expr::EvalResult Result;
+    if (rex->Evaluate(Result, Context) && !Result.HasSideEffects &&
+        Result.Val.getInt() != 0 && Result.Val.getInt() != 1) {
+      Diag(Loc, diag::warn_logical_instead_of_bitwise)
+       << rex->getSourceRange()
+        << (Opc == BinaryOperator::LAnd ? "&&" : "||")
+        << (Opc == BinaryOperator::LAnd ? "&" : "|");
+    }
+  }
   
   if (!Context.getLangOptions().CPlusPlus) {
     UsualUnaryConversions(lex);

Modified: cfe/trunk/test/CodeGenCXX/static-init-2.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/static-init-2.cpp?rev=109314&r1=109313&r2=109314&view=diff
==============================================================================
--- cfe/trunk/test/CodeGenCXX/static-init-2.cpp (original)
+++ cfe/trunk/test/CodeGenCXX/static-init-2.cpp Fri Jul 23 20:10:11 2010
@@ -3,4 +3,4 @@
 // Make sure we don't crash generating y; its value is constant, but the
 // initializer has side effects, so EmitConstantExpr should fail.
 int x();
-int y = x() && 0;   // expected-warning {{use of logical && with constant operand}}
+int y = x() && 0;

Modified: cfe/trunk/test/Sema/exprs.c
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/exprs.c?rev=109314&r1=109313&r2=109314&view=diff
==============================================================================
--- cfe/trunk/test/Sema/exprs.c (original)
+++ cfe/trunk/test/Sema/exprs.c Fri Jul 23 20:10:11 2010
@@ -145,5 +145,8 @@
 int test20(int x) {
   return x && 4; // expected-warning {{use of logical && with constant operand; switch to bitwise & or remove constant}}
 
-  return x && sizeof(int) == 4;  // no warning.
+  return x && sizeof(int) == 4;  // no warning, RHS is logical op.
+  
+  // no warning, this is an idiom for "true" in old C style.
+  return x && (signed char)1;
 }

Modified: cfe/trunk/test/Sema/switch.c
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/switch.c?rev=109314&r1=109313&r2=109314&view=diff
==============================================================================
--- cfe/trunk/test/Sema/switch.c (original)
+++ cfe/trunk/test/Sema/switch.c Fri Jul 23 20:10:11 2010
@@ -50,14 +50,12 @@
   }
   
   switch (cond) {
-  case g() && 0: // expected-error {{expression is not an integer constant expression}} // expected-note {{subexpression not valid in an integer constant expression}} \
-                    expected-warning {{use of logical && with constant operand}}
+  case g() && 0: // expected-error {{expression is not an integer constant expression}} // expected-note {{subexpression not valid in an integer constant expression}}
     break;
   }
   
   switch (cond) {
-  case 0 ... g() || 1: // expected-error {{expression is not an integer constant expression}} // expected-note {{subexpression not valid in an integer constant expression}} \\
-                          expected-warning {{use of logical || with constant operand}}
+  case 0 ... g() || 1: // expected-error {{expression is not an integer constant expression}} // expected-note {{subexpression not valid in an integer constant expression}}
     break;
   }
 }

Modified: cfe/trunk/test/SemaCXX/switch.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/switch.cpp?rev=109314&r1=109313&r2=109314&view=diff
==============================================================================
--- cfe/trunk/test/SemaCXX/switch.cpp (original)
+++ cfe/trunk/test/SemaCXX/switch.cpp Fri Jul 23 20:10:11 2010
@@ -8,8 +8,7 @@
   }
 
   int n = 3;
-  switch (n && 1) { // expected-warning {{bool}} \
-                    // expected-warning {{use of logical && with constant operand}}
+  switch (n && 1) { // expected-warning {{bool}}
     case 1:
       break;
   }