In vector comparisons, handle scalar LHS just as we handle scalar RHS

Summary: Fixes PR27258

Reviewers: rsmith

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D19123

llvm-svn: 266366

1 files changed, 11 insertions, 9 deletions

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index fcc608fa1f5..bd56596446e 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -7929,14 +7929,16 @@ QualType Sema::CheckVectorOperands(ExprResult &LHS, ExprResult &RHS,
       return RHSType;
   }
 
-  // If we're allowing lax vector conversions, only the total (data) size
-  // needs to be the same.
-  // FIXME: Should we really be allowing this?
-  // FIXME: We really just pick the LHS type arbitrarily?
-  if (isLaxVectorConversion(RHSType, LHSType)) {
-    QualType resultType = LHSType;
-    RHS = ImpCastExprToType(RHS.get(), resultType, CK_BitCast);
-    return resultType;
+  // If we're allowing lax vector conversions, only the total (data) size needs
+  // to be the same. If one of the types is scalar, the result is always the
+  // vector type. Don't allow this if the scalar operand is an lvalue.
+  QualType VecType = LHSVecType ? LHSType : RHSType;
+  QualType ScalarType = LHSVecType ? RHSType : LHSType;
+  ExprResult *ScalarExpr = LHSVecType ? &RHS : &LHS;
+  if (isLaxVectorConversion(ScalarType, VecType) &&
+      !ScalarExpr->get()->isLValue()) {
+    *ScalarExpr = ImpCastExprToType(ScalarExpr->get(), VecType, CK_BitCast);
+    return VecType;
   }
 
   // Okay, the expression is invalid.
@@ -9480,7 +9482,7 @@ QualType Sema::CheckVectorCompareOperands(ExprResult &LHS, ExprResult &RHS,
   }
   
   // Return a signed type for the vector.
-  return GetSignedVectorType(LHSType);
+  return GetSignedVectorType(vType);
 }
 
 QualType Sema::CheckVectorLogicalOperands(ExprResult &LHS, ExprResult &RHS,