1 files changed, 90 insertions, 1 deletions

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index d5416d4d057..533b3b7da9f 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -1250,6 +1250,93 @@ static QualType handleComplexIntConversion(Sema &S, ExprResult &LHS,
   return ComplexType;
 }
 
+/// Return the rank of a given fixed point or integer type. The value itself
+/// doesn't matter, but the values must be increasing with proper increasing
+/// rank as described in N1169 4.1.1.
+static unsigned GetFixedPointRank(QualType Ty) {
+  const auto *BTy = Ty->getAs<BuiltinType>();
+  assert(BTy && "Expected a builtin type.");
+
+  switch (BTy->getKind()) {
+  case BuiltinType::ShortFract:
+  case BuiltinType::UShortFract:
+  case BuiltinType::SatShortFract:
+  case BuiltinType::SatUShortFract:
+    return 1;
+  case BuiltinType::Fract:
+  case BuiltinType::UFract:
+  case BuiltinType::SatFract:
+  case BuiltinType::SatUFract:
+    return 2;
+  case BuiltinType::LongFract:
+  case BuiltinType::ULongFract:
+  case BuiltinType::SatLongFract:
+  case BuiltinType::SatULongFract:
+    return 3;
+  case BuiltinType::ShortAccum:
+  case BuiltinType::UShortAccum:
+  case BuiltinType::SatShortAccum:
+  case BuiltinType::SatUShortAccum:
+    return 4;
+  case BuiltinType::Accum:
+  case BuiltinType::UAccum:
+  case BuiltinType::SatAccum:
+  case BuiltinType::SatUAccum:
+    return 5;
+  case BuiltinType::LongAccum:
+  case BuiltinType::ULongAccum:
+  case BuiltinType::SatLongAccum:
+  case BuiltinType::SatULongAccum:
+    return 6;
+  default:
+    if (BTy->isInteger())
+      return 0;
+    llvm_unreachable("Unexpected fixed point or integer type");
+  }
+}
+
+/// handleFixedPointConversion - Fixed point operations between fixed
+/// point types and integers or other fixed point types do not fall under
+/// usual arithmetic conversion since these conversions could result in loss
+/// of precsision (N1169 4.1.4). These operations should be calculated with
+/// the full precision of their result type (N1169 4.1.6.2.1).
+static QualType handleFixedPointConversion(Sema &S, QualType LHSTy,
+                                           QualType RHSTy) {
+  assert((LHSTy->isFixedPointType() || RHSTy->isFixedPointType()) &&
+         "Expected at least one of the operands to be a fixed point type");
+  assert((LHSTy->isFixedPointOrIntegerType() ||
+          RHSTy->isFixedPointOrIntegerType()) &&
+         "Special fixed point arithmetic operation conversions are only "
+         "applied to ints or other fixed point types");
+
+  // If one operand has signed fixed-point type and the other operand has
+  // unsigned fixed-point type, then the unsigned fixed-point operand is
+  // converted to its corresponding signed fixed-point type and the resulting
+  // type is the type of the converted operand.
+  if (RHSTy->isSignedFixedPointType() && LHSTy->isUnsignedFixedPointType())
+    LHSTy = S.Context.getCorrespondingSignedFixedPointType(LHSTy);
+  else if (RHSTy->isUnsignedFixedPointType() && LHSTy->isSignedFixedPointType())
+    RHSTy = S.Context.getCorrespondingSignedFixedPointType(RHSTy);
+
+  // The result type is the type with the highest rank, whereby a fixed-point
+  // conversion rank is always greater than an integer conversion rank; if the
+  // type of either of the operands is a saturating fixedpoint type, the result
+  // type shall be the saturating fixed-point type corresponding to the type
+  // with the highest rank; the resulting value is converted (taking into
+  // account rounding and overflow) to the precision of the resulting type.
+  // Same ranks between signed and unsigned types are resolved earlier, so both
+  // types are either signed or both unsigned at this point.
+  unsigned LHSTyRank = GetFixedPointRank(LHSTy);
+  unsigned RHSTyRank = GetFixedPointRank(RHSTy);
+
+  QualType ResultTy = LHSTyRank > RHSTyRank ? LHSTy : RHSTy;
+
+  if (LHSTy->isSaturatedFixedPointType() || RHSTy->isSaturatedFixedPointType())
+    ResultTy = S.Context.getCorrespondingSaturatedType(ResultTy);
+
+  return ResultTy;
+}
+
 /// UsualArithmeticConversions - Performs various conversions that are common to
 /// binary operators (C99 6.3.1.8). If both operands aren't arithmetic, this
 /// routine returns the first non-arithmetic type found. The client is
@@ -1322,12 +1409,14 @@ QualType Sema::UsualArithmeticConversions(ExprResult &LHS, ExprResult &RHS,
     return handleComplexIntConversion(*this, LHS, RHS, LHSType, RHSType,
                                       IsCompAssign);
 
+  if (LHSType->isFixedPointType() || RHSType->isFixedPointType())
+    return handleFixedPointConversion(*this, LHSType, RHSType);
+
   // Finally, we have two differing integer types.
   return handleIntegerConversion<doIntegralCast, doIntegralCast>
            (*this, LHS, RHS, LHSType, RHSType, IsCompAssign);
 }
 
-
 //===----------------------------------------------------------------------===//
 //  Semantic Analysis for various Expression Types
 //===----------------------------------------------------------------------===//