[PATCH] D24861: [Sema] extend Wshift-op-parentheses so it warns for multiplicative operators

[Daniel Marjamäki via cfe-commits]

danielmarjamaki removed rL LLVM as the repository for this revision.
danielmarjamaki updated this revision to Diff 72797.
danielmarjamaki added a comment.

Don't write warning for multiplication in LHS of <<. Often the execution order is not important.


https://reviews.llvm.org/D24861

Files:
  lib/Sema/SemaExpr.cpp
  test/Sema/parentheses.cpp

Index: test/Sema/parentheses.cpp
===================================================================
--- test/Sema/parentheses.cpp
+++ test/Sema/parentheses.cpp
@@ -95,6 +95,23 @@
   // CHECK: fix-it:"{{.*}}":{[[@LINE-2]]:10-[[@LINE-2]]:10}:"("
   // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:15-[[@LINE-3]]:15}:")"
 
+  (void)(a >> b * c); // expected-warning {{operator '>>' has lower precedence than '*'; '*' will be evaluated first}} \
+                         expected-note {{place parentheses around the '*' expression to silence this warning}}
+  // CHECK: fix-it:"{{.*}}":{[[@LINE-2]]:15-[[@LINE-2]]:15}:"("
+  // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:20-[[@LINE-3]]:20}:")"
+
+  (void)(a / b << c); // expected-warning {{operator '<<' has lower precedence than '/'; '/' will be evaluated first}} \
+                         expected-note {{place parentheses around the '/' expression to silence this warning}}
+  // CHECK: fix-it:"{{.*}}":{[[@LINE-2]]:10-[[@LINE-2]]:10}:"("
+  // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:15-[[@LINE-3]]:15}:")"
+
+  (void)(a % b << c); // expected-warning {{operator '<<' has lower precedence than '%'; '%' will be evaluated first}} \
+                         expected-note {{place parentheses around the '%' expression to silence this warning}}
+  // CHECK: fix-it:"{{.*}}":{[[@LINE-2]]:10-[[@LINE-2]]:10}:"("
+  // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:15-[[@LINE-3]]:15}:")"
+
+  (void)(a * b << c); // no warning, often the execution order does not matter.
+
   Stream() << b + c;
   Stream() >> b + c; // expected-warning {{operator '>>' has lower precedence than '+'; '+' will be evaluated first}} \
                         expected-note {{place parentheses around the '+' expression to silence this warning}}
Index: lib/Sema/SemaExpr.cpp
===================================================================
--- lib/Sema/SemaExpr.cpp
+++ lib/Sema/SemaExpr.cpp
@@ -11246,18 +11246,24 @@
   }
 }
 
-static void DiagnoseAdditionInShift(Sema &S, SourceLocation OpLoc,
-                                    Expr *SubExpr, StringRef Shift) {
-  if (BinaryOperator *Bop = dyn_cast<BinaryOperator>(SubExpr)) {
-    if (Bop->getOpcode() == BO_Add || Bop->getOpcode() == BO_Sub) {
-      StringRef Op = Bop->getOpcodeStr();
-      S.Diag(Bop->getOperatorLoc(), diag::warn_addition_in_bitshift)
-          << Bop->getSourceRange() << OpLoc << Shift << Op;
-      SuggestParentheses(S, Bop->getOperatorLoc(),
-          S.PDiag(diag::note_precedence_silence) << Op,
-          Bop->getSourceRange());
-    }
-  }
+static void DiagnoseAddOrMulInShift(Sema &S, SourceLocation OpLoc,
+                                    Expr *SubExpr, StringRef Shift,
+                                    bool ShiftLeftLHS) {
+  BinaryOperator *Bop = dyn_cast<BinaryOperator>(SubExpr);
+  if (!Bop)
+    return;
+  if (!Bop->isAdditiveOp() && !Bop->isMultiplicativeOp())
+    return;
+  // In many cases, execution order does not matter for 'A*B<<C'.
+  if (ShiftLeftLHS && Bop->getOpcode() == BO_Mul)
+    return;
+
+  StringRef Op = Bop->getOpcodeStr();
+  S.Diag(Bop->getOperatorLoc(), diag::warn_addition_in_bitshift)
+      << Bop->getSourceRange() << OpLoc << Shift << Op;
+  SuggestParentheses(S, Bop->getOperatorLoc(),
+                     S.PDiag(diag::note_precedence_silence) << Op,
+                     Bop->getSourceRange());
 }
 
 static void DiagnoseShiftCompare(Sema &S, SourceLocation OpLoc,
@@ -11313,8 +11319,8 @@
   if ((Opc == BO_Shl && LHSExpr->getType()->isIntegralType(Self.getASTContext()))
       || Opc == BO_Shr) {
     StringRef Shift = BinaryOperator::getOpcodeStr(Opc);
-    DiagnoseAdditionInShift(Self, OpLoc, LHSExpr, Shift);
-    DiagnoseAdditionInShift(Self, OpLoc, RHSExpr, Shift);
+    DiagnoseAddOrMulInShift(Self, OpLoc, LHSExpr, Shift, Opc == BO_Shl);
+    DiagnoseAddOrMulInShift(Self, OpLoc, RHSExpr, Shift, false);
   }
 
   // Warn on overloaded shift operators and comparisons, such as:


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