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
diff --git a/lib/AST/ExprConstant.cpp b/lib/AST/ExprConstant.cpp
index a472951..338cd74 100644
--- a/lib/AST/ExprConstant.cpp
+++ b/lib/AST/ExprConstant.cpp
@@ -4708,9 +4708,14 @@
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 @@
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 eb62343..7ec4bc2 100644
--- a/lib/CodeGen/CGExprScalar.cpp
+++ b/lib/CodeGen/CGExprScalar.cpp
@@ -429,6 +429,8 @@
// 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 @@
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 @@
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 @@
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 @@
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 b714910..bac8977 100644
--- a/lib/Sema/SemaExpr.cpp
+++ b/lib/Sema/SemaExpr.cpp
@@ -6578,6 +6578,11 @@
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() ||
diff --git a/test/CodeGen/catch-undef-behavior.c b/test/CodeGen/catch-undef-behavior.c
index d0b6d19..9170666 100644
--- a/test/CodeGen/catch-undef-behavior.c
+++ b/test/CodeGen/catch-undef-behavior.c
@@ -99,7 +99,7 @@
// CHECK: @rsh_inbounds
int rsh_inbounds(int a, int b) {
- // CHECK: %[[INBOUNDS:.*]] = icmp ult i32 %[[RHS:.*]], 32
+ // CHECK: %[[INBOUNDS:.*]] = icmp ule i32 %[[RHS:.*]], 31
// CHECK: br i1 %[[INBOUNDS]]
// CHECK: %[[ARG1:.*]] = zext
diff --git a/test/CodeGenOpenCL/shifts.cl b/test/CodeGenOpenCL/shifts.cl
new file mode 100644
index 0000000..b84ec1e
--- /dev/null
+++ b/test/CodeGenOpenCL/shifts.cl
@@ -0,0 +1,28 @@
+// RUN: %clang_cc1 -x cl -O1 -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s
+// OpenCL essentially reduces all shift amounts to the last word-size bits before evaluating.
+// Test this both for variables and constants evaluated in the front-end.
+
+
+//CHECK: @positiveShift32
+int positiveShift32(int a,int b) {
+ //CHECK: %shl.mask = and i32 %b, 31
+ //CHECK-NEXT: %shl = shl i32 %a, %shl.mask
+ int c = a<<b;
+ int d = ((int)1)<<33;
+ //CHECK-NEXT: %add = add nsw i32 %shl, 2
+ int e = c + d;
+ //CHECK-NEXT: ret i32 %add
+ return e;
+}
+
+//CHECK: @positiveShift64
+long positiveShift64(long a,long b) {
+ //CHECK: %shr.mask = and i64 %b, 63
+ //CHECK-NEXT: %shr = ashr i64 %a, %shr.mask
+ long c = a>>b;
+ long d = ((long)8)>>65;
+ //CHECK-NEXT: %add = add nsw i64 %shr, 4
+ long e = c + d;
+ //CHECK-NEXT: ret i64 %add
+ return e;
+}
diff --git a/test/Sema/shiftOpenCL.cl b/test/Sema/shiftOpenCL.cl
new file mode 100644
index 0000000..3bf9718
--- /dev/null
+++ b/test/Sema/shiftOpenCL.cl
@@ -0,0 +1,14 @@
+// RUN: %clang_cc1 -x cl -O1 -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s
+// OpenCL essentially reduces all shift amounts to the last word-size bits before evaluating.
+// Test this both for variables and constants evaluated in the front-end.
+
+//CHECK: @array0 = common global [256 x i8]
+char array0[((int)1)<<40];
+//CHECK: @array1 = common global [256 x i8]
+char array1[((int)1)<<(-24)];
+
+//CHECK: @negativeShift32
+int negativeShift32(int a,int b) {
+ //CHECK: ret i32 65536
+ return ((int)1)<<(-16);
+}