Extend -Wtautological-overlap-compare to more cases.

Previously, -Wtautological-overlap-compare did not warn on cases where the
boolean expression was in an assignment or return statement.  This patch
should cause all boolean statements to be passed to the tautological compare
checks in the CFG analysis.

This is one of the issues from PR13101

llvm-svn: 290920

1 files changed, 7 insertions, 3 deletions

diff --git a/clang/lib/Analysis/CFG.cpp b/clang/lib/Analysis/CFG.cpp
index bf3cc05cdb6..a1a463f1d03 100644
--- a/clang/lib/Analysis/CFG.cpp
+++ b/clang/lib/Analysis/CFG.cpp
@@ -1690,15 +1690,19 @@ CFGBuilder::VisitLogicalOperator(BinaryOperator *B,
     // we have been provided.
     ExitBlock = RHSBlock = createBlock(false);
 
+    // Even though KnownVal is only used in the else branch of the next
+    // conditional, tryEvaluateBool performs additional checking on the
+    // Expr, so it should be called unconditionally.
+    TryResult KnownVal = tryEvaluateBool(RHS);
+    if (!KnownVal.isKnown())
+      KnownVal = tryEvaluateBool(B);
+
     if (!Term) {
       assert(TrueBlock == FalseBlock);
       addSuccessor(RHSBlock, TrueBlock);
     }
     else {
       RHSBlock->setTerminator(Term);
-      TryResult KnownVal = tryEvaluateBool(RHS);
-      if (!KnownVal.isKnown())
-        KnownVal = tryEvaluateBool(B);
       addSuccessor(RHSBlock, TrueBlock, !KnownVal.isFalse());
       addSuccessor(RHSBlock, FalseBlock, !KnownVal.isTrue());
     }