Scalar shifts in the OpenCL specification (as of v. 1.2) are defined to be

with respect to the lower "left-hand-side bitwidth" bits, even when negative);
see OpenCL spec 6.3j. This patch both implements this behaviour in the code
generator and "constant folding" bits of Sema, and also prevents tests
to detect undefinedness in terms of the weaker C99 or C++ specifications
from being applied. 


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@171755 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 41 insertions, 17 deletions

diff --git a/lib/AST/ExprConstant.cpp b/lib/AST/ExprConstant.cpp
index a472951ab6..338cd74b32 100644
--- a/lib/AST/ExprConstant.cpp
+++ b/lib/AST/ExprConstant.cpp
@@ -4708,9 +4708,14 @@ bool DataRecursiveIntBinOpEvaluator::
       return Success(E->getOpcode() == BO_Rem ? LHS % RHS : LHS / RHS, E,
                      Result);
     case BO_Shl: {
-      // During constant-folding, a negative shift is an opposite shift. Such
-      // a shift is not a constant expression.
-      if (RHS.isSigned() && RHS.isNegative()) {
+      if (Info.getLangOpts().OpenCL)
+        // OpenCL 6.3j: shift values are effectively % word size of LHS.
+        RHS &= APSInt(llvm::APInt(LHS.getBitWidth(),
+                      static_cast<uint64_t>(LHS.getBitWidth() - 1)),
+                      RHS.isUnsigned());
+      else if (RHS.isSigned() && RHS.isNegative()) {
+        // During constant-folding, a negative shift is an opposite shift. Such
+        // a shift is not a constant expression.
         CCEDiag(E, diag::note_constexpr_negative_shift) << RHS;
         RHS = -RHS;
         goto shift_right;
@@ -4735,9 +4740,14 @@ bool DataRecursiveIntBinOpEvaluator::
       return Success(LHS << SA, E, Result);
     }
     case BO_Shr: {
-      // During constant-folding, a negative shift is an opposite shift. Such a
-      // shift is not a constant expression.
-      if (RHS.isSigned() && RHS.isNegative()) {
+      if (Info.getLangOpts().OpenCL)
+        // OpenCL 6.3j: shift values are effectively % word size of LHS.
+        RHS &= APSInt(llvm::APInt(LHS.getBitWidth(),
+                      static_cast<uint64_t>(LHS.getBitWidth() - 1)),
+                      RHS.isUnsigned());
+      else if (RHS.isSigned() && RHS.isNegative()) {
+        // During constant-folding, a negative shift is an opposite shift. Such a
+        // shift is not a constant expression.
         CCEDiag(E, diag::note_constexpr_negative_shift) << RHS;
         RHS = -RHS;
         goto shift_left;
diff --git a/lib/CodeGen/CGExprScalar.cpp b/lib/CodeGen/CGExprScalar.cpp
index eb62343bc6..7ec4bc2297 100644
--- a/lib/CodeGen/CGExprScalar.cpp
+++ b/lib/CodeGen/CGExprScalar.cpp
@@ -429,6 +429,8 @@ public:
   // Check for undefined division and modulus behaviors.
   void EmitUndefinedBehaviorIntegerDivAndRemCheck(const BinOpInfo &Ops, 
                                                   llvm::Value *Zero,bool isDiv);
+  // Common helper for getting how wide LHS of shift is.
+  static Value *GetWidthMinusOneValue(Value* LHS,Value* RHS);
   Value *EmitDiv(const BinOpInfo &Ops);
   Value *EmitRem(const BinOpInfo &Ops);
   Value *EmitAdd(const BinOpInfo &Ops);
@@ -2365,6 +2367,11 @@ Value *ScalarExprEmitter::EmitSub(const BinOpInfo &op) {
   return Builder.CreateExactSDiv(diffInChars, divisor, "sub.ptr.div");
 }
 
+Value *ScalarExprEmitter::GetWidthMinusOneValue(Value* LHS,Value* RHS) {
+  unsigned Width = cast<llvm::IntegerType>(LHS->getType())->getBitWidth();
+  return llvm::ConstantInt::get(RHS->getType(), Width - 1);
+}
+
 Value *ScalarExprEmitter::EmitShl(const BinOpInfo &Ops) {
   // LLVM requires the LHS and RHS to be the same type: promote or truncate the
   // RHS to the same size as the LHS.
@@ -2372,11 +2379,9 @@ Value *ScalarExprEmitter::EmitShl(const BinOpInfo &Ops) {
   if (Ops.LHS->getType() != RHS->getType())
     RHS = Builder.CreateIntCast(RHS, Ops.LHS->getType(), false, "sh_prom");
 
-  if (CGF.getLangOpts().SanitizeShift &&
-      isa<llvm::IntegerType>(Ops.LHS->getType())) {
-    unsigned Width = cast<llvm::IntegerType>(Ops.LHS->getType())->getBitWidth();
-    llvm::Value *WidthMinusOne =
-      llvm::ConstantInt::get(RHS->getType(), Width - 1);
+  if (CGF.getLangOpts().SanitizeShift && !CGF.getLangOpts().OpenCL
+      && isa<llvm::IntegerType>(Ops.LHS->getType())) {
+    llvm::Value *WidthMinusOne = GetWidthMinusOneValue(Ops.LHS, RHS);
     // FIXME: Emit the branching explicitly rather than emitting the check
     // twice.
     EmitBinOpCheck(Builder.CreateICmpULE(RHS, WidthMinusOne), Ops);
@@ -2401,6 +2406,9 @@ Value *ScalarExprEmitter::EmitShl(const BinOpInfo &Ops) {
       EmitBinOpCheck(Builder.CreateICmpEQ(BitsShiftedOff, Zero), Ops);
     }
   }
+  // OpenCL 6.3j: shift values are effectively % word size of LHS.
+  if (CGF.getLangOpts().OpenCL)
+    RHS = Builder.CreateAnd(RHS, GetWidthMinusOneValue(Ops.LHS, RHS), "shl.mask");
 
   return Builder.CreateShl(Ops.LHS, RHS, "shl");
 }
@@ -2412,12 +2420,13 @@ Value *ScalarExprEmitter::EmitShr(const BinOpInfo &Ops) {
   if (Ops.LHS->getType() != RHS->getType())
     RHS = Builder.CreateIntCast(RHS, Ops.LHS->getType(), false, "sh_prom");
 
-  if (CGF.getLangOpts().SanitizeShift &&
-      isa<llvm::IntegerType>(Ops.LHS->getType())) {
-    unsigned Width = cast<llvm::IntegerType>(Ops.LHS->getType())->getBitWidth();
-    llvm::Value *WidthVal = llvm::ConstantInt::get(RHS->getType(), Width);
-    EmitBinOpCheck(Builder.CreateICmpULT(RHS, WidthVal), Ops);
-  }
+  if (CGF.getLangOpts().SanitizeShift && !CGF.getLangOpts().OpenCL
+      && isa<llvm::IntegerType>(Ops.LHS->getType()))
+    EmitBinOpCheck(Builder.CreateICmpULE(RHS, GetWidthMinusOneValue(Ops.LHS, RHS)), Ops);
+
+  // OpenCL 6.3j: shift values are effectively % word size of LHS.
+  if (CGF.getLangOpts().OpenCL)
+    RHS = Builder.CreateAnd(RHS, GetWidthMinusOneValue(Ops.LHS, RHS), "shr.mask");
 
   if (Ops.Ty->hasUnsignedIntegerRepresentation())
     return Builder.CreateLShr(Ops.LHS, RHS, "shr");
diff --git a/lib/Sema/SemaExpr.cpp b/lib/Sema/SemaExpr.cpp
index b71491008b..bac897748f 100644
--- a/lib/Sema/SemaExpr.cpp
+++ b/lib/Sema/SemaExpr.cpp
@@ -6578,6 +6578,11 @@ static bool isScopedEnumerationType(QualType T) {
 static void DiagnoseBadShiftValues(Sema& S, ExprResult &LHS, ExprResult &RHS,
                                    SourceLocation Loc, unsigned Opc,
                                    QualType LHSType) {
+  // OpenCL 6.3j: shift values are effectively % word size of LHS (more defined),
+  // so skip remaining warnings as we don't want to modify values within Sema.
+  if (S.getLangOpts().OpenCL)
+    return;
+
   llvm::APSInt Right;
   // Check right/shifter operand
   if (RHS.get()->isValueDependent() ||