Hi,
with this change, the following compiles to "ret i32 undef":
int main(int argc, char **argv) {
constexpr int x = 1;
constexpr int y = 2;
int z;
__builtin_sadd_overflow(x, y, &z);
return z;
}
On Wed, Jun 13, 2018 at 1:43 PM, Erich Keane via cfe-commits <
cfe-commits@lists.llvm.org> wrote:
> Author: erichkeane
> Date: Wed Jun 13 13:43:27 2018
> New Revision: 334650
>
> URL: http://llvm.org/viewvc/llvm-project?rev=334650&view=rev
> Log:
> Implement constexpr __builtin_*_overflow
>
> As requested here:https://bugs.llvm.org/show_bug.cgi?id=37633
> permit the __builtin_*_overflow builtins in constexpr functions.
>
> Differential Revision: https://reviews.llvm.org/D48040
>
> Modified:
> cfe/trunk/lib/AST/ExprConstant.cpp
> cfe/trunk/test/SemaCXX/builtins-overflow.cpp
>
> Modified: cfe/trunk/lib/AST/ExprConstant.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/
> ExprConstant.cpp?rev=334650&r1=334649&r2=334650&view=diff
> ============================================================
> ==================
> --- cfe/trunk/lib/AST/ExprConstant.cpp (original)
> +++ cfe/trunk/lib/AST/ExprConstant.cpp Wed Jun 13 13:43:27 2018
> @@ -8155,6 +8155,124 @@ bool IntExprEvaluator::VisitBuiltinCallE
> case Builtin::BIomp_is_initial_device:
> // We can decide statically which value the runtime would return if
> called.
> return Success(Info.getLangOpts().OpenMPIsDevice ? 0 : 1, E);
> + case Builtin::BI__builtin_add_overflow:
> + case Builtin::BI__builtin_sub_overflow:
> + case Builtin::BI__builtin_mul_overflow:
> + case Builtin::BI__builtin_sadd_overflow:
> + case Builtin::BI__builtin_uadd_overflow:
> + case Builtin::BI__builtin_uaddl_overflow:
> + case Builtin::BI__builtin_uaddll_overflow:
> + case Builtin::BI__builtin_usub_overflow:
> + case Builtin::BI__builtin_usubl_overflow:
> + case Builtin::BI__builtin_usubll_overflow:
> + case Builtin::BI__builtin_umul_overflow:
> + case Builtin::BI__builtin_umull_overflow:
> + case Builtin::BI__builtin_umulll_overflow:
> + case Builtin::BI__builtin_saddl_overflow:
> + case Builtin::BI__builtin_saddll_overflow:
> + case Builtin::BI__builtin_ssub_overflow:
> + case Builtin::BI__builtin_ssubl_overflow:
> + case Builtin::BI__builtin_ssubll_overflow:
> + case Builtin::BI__builtin_smul_overflow:
> + case Builtin::BI__builtin_smull_overflow:
> + case Builtin::BI__builtin_smulll_overflow: {
> + LValue ResultLValue;
> + APSInt LHS, RHS;
> +
> + QualType ResultType = E->getArg(2)->getType()->getPointeeType();
> + if (!EvaluateInteger(E->getArg(0), LHS, Info) ||
> + !EvaluateInteger(E->getArg(1), RHS, Info) ||
> + !EvaluatePointer(E->getArg(2), ResultLValue, Info))
> + return false;
> +
> + APSInt Result;
> + bool DidOverflow = false;
> +
> + // If the types don't have to match, enlarge all 3 to the largest of
> them.
> + if (BuiltinOp == Builtin::BI__builtin_add_overflow ||
> + BuiltinOp == Builtin::BI__builtin_sub_overflow ||
> + BuiltinOp == Builtin::BI__builtin_mul_overflow) {
> + bool IsSigned = LHS.isSigned() || RHS.isSigned() ||
> + ResultType->isSignedIntegerOrEnumerationType();
> + bool AllSigned = LHS.isSigned() && RHS.isSigned() &&
> + ResultType->isSignedIntegerOrEnumerationType();
> + uint64_t LHSSize = LHS.getBitWidth();
> + uint64_t RHSSize = RHS.getBitWidth();
> + uint64_t ResultSize = Info.Ctx.getTypeSize(ResultType);
> + uint64_t MaxBits = std::max(std::max(LHSSize, RHSSize), ResultSize);
> +
> + // Add an additional bit if the signedness isn't uniformly agreed
> to. We
> + // could do this ONLY if there is a signed and an unsigned that
> both have
> + // MaxBits, but the code to check that is pretty nasty. The issue
> will be
> + // caught in the shrink-to-result later anyway.
> + if (IsSigned && !AllSigned)
> + ++MaxBits;
> +
> + LHS = APSInt(IsSigned ? LHS.sextOrSelf(MaxBits) :
> LHS.zextOrSelf(MaxBits),
> + !IsSigned);
> + RHS = APSInt(IsSigned ? RHS.sextOrSelf(MaxBits) :
> RHS.zextOrSelf(MaxBits),
> + !IsSigned);
> + Result = APSInt(MaxBits, !IsSigned);
> + }
> +
> + // Find largest int.
> + switch (BuiltinOp) {
> + default:
> + llvm_unreachable("Invalid value for BuiltinOp");
> + case Builtin::BI__builtin_add_overflow:
> + case Builtin::BI__builtin_sadd_overflow:
> + case Builtin::BI__builtin_saddl_overflow:
> + case Builtin::BI__builtin_saddll_overflow:
> + case Builtin::BI__builtin_uadd_overflow:
> + case Builtin::BI__builtin_uaddl_overflow:
> + case Builtin::BI__builtin_uaddll_overflow:
> + Result = LHS.isSigned() ? LHS.sadd_ov(RHS, DidOverflow)
> + : LHS.uadd_ov(RHS, DidOverflow);
> + break;
> + case Builtin::BI__builtin_sub_overflow:
> + case Builtin::BI__builtin_ssub_overflow:
> + case Builtin::BI__builtin_ssubl_overflow:
> + case Builtin::BI__builtin_ssubll_overflow:
> + case Builtin::BI__builtin_usub_overflow:
> + case Builtin::BI__builtin_usubl_overflow:
> + case Builtin::BI__builtin_usubll_overflow:
> + Result = LHS.isSigned() ? LHS.ssub_ov(RHS, DidOverflow)
> + : LHS.usub_ov(RHS, DidOverflow);
> + break;
> + case Builtin::BI__builtin_mul_overflow:
> + case Builtin::BI__builtin_smul_overflow:
> + case Builtin::BI__builtin_smull_overflow:
> + case Builtin::BI__builtin_smulll_overflow:
> + case Builtin::BI__builtin_umul_overflow:
> + case Builtin::BI__builtin_umull_overflow:
> + case Builtin::BI__builtin_umulll_overflow:
> + Result = LHS.isSigned() ? LHS.smul_ov(RHS, DidOverflow)
> + : LHS.umul_ov(RHS, DidOverflow);
> + break;
> + }
> +
> + // In the case where multiple sizes are allowed, truncate and see if
> + // the values are the same.
> + if (BuiltinOp == Builtin::BI__builtin_add_overflow ||
> + BuiltinOp == Builtin::BI__builtin_sub_overflow ||
> + BuiltinOp == Builtin::BI__builtin_mul_overflow) {
> + // APSInt doesn't have a TruncOrSelf, so we use extOrTrunc instead,
> + // since it will give us the behavior of a TruncOrSelf in the case
> where
> + // its parameter <= its size. We previously set Result to be at
> least the
> + // type-size of the result, so getTypeSize(ResultType) <=
> Result.BitWidth
> + // will work exactly like TruncOrSelf.
> + APSInt Temp = Result.extOrTrunc(Info.Ctx.getTypeSize(ResultType));
> + Temp.setIsSigned(ResultType->isSignedIntegerOrEnumerationType());
> +
> + if (!APSInt::isSameValue(Temp, Result))
> + DidOverflow = true;
> + Result = Temp;
> + }
> +
> + APValue APV{Result};
> + handleAssignment(Info, E, ResultLValue, ResultType, APV);
> + return Success(DidOverflow, E);
> + }
> }
> }
>
>
> Modified: cfe/trunk/test/SemaCXX/builtins-overflow.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/
> SemaCXX/builtins-overflow.cpp?rev=334650&r1=334649&r2=334650&view=diff
> ============================================================
> ==================
> --- cfe/trunk/test/SemaCXX/builtins-overflow.cpp (original)
> +++ cfe/trunk/test/SemaCXX/builtins-overflow.cpp Wed Jun 13 13:43:27 2018
> @@ -1,6 +1,8 @@
> // RUN: %clang_cc1 -fsyntax-only -std=c++17 -verify %s
> // expected-no-diagnostics
>
> +#include <limits.h>
> +
> int a() {
> const int x = 3;
> static int z;
> @@ -13,3 +15,85 @@ int a2() {
> constexpr int *y = &z;
> return []() { return __builtin_sub_overflow(x, x, y); }();
> }
> +
> +template<typename T>
> +struct Result {
> + bool B;
> + T Value;
> + constexpr bool operator==(const Result<T> &Other) {
> + return B == Other.B && Value == Other.Value;
> + }
> +};
> +
> +
> +template <typename RET, typename LHS, typename RHS>
> +constexpr Result<RET> add(LHS &&lhs, RHS &&rhs) {
> + RET sum{};
> + bool b = __builtin_add_overflow(lhs, rhs, &sum);
> + return {b, sum};
> +}
> +
> +static_assert(add<short>(static_cast<char>(120), static_cast<char>(10))
> == Result<short>{false, 130});
> +static_assert(add<char>(static_cast<short>(120), static_cast<short>(10))
> == Result<char>{true, -126});
> +static_assert(add<unsigned int>(INT_MAX, INT_MAX) == Result<unsigned
> int>{false, static_cast<unsigned int>(INT_MAX) * 2u});
> +static_assert(add<int>(static_cast<unsigned int>(INT_MAX), 1u) ==
> Result<int>{true, INT_MIN});
> +
> +static_assert(add<int>(17, 22) == Result<int>{false, 39});
> +static_assert(add<int>(INT_MAX - 22, 24) == Result<int>{true, INT_MIN +
> 1});
> +static_assert(add<int>(INT_MIN + 22, -23) == Result<int>{true, INT_MAX});
> +
> +template <typename RET, typename LHS, typename RHS>
> +constexpr Result<RET> sub(LHS &&lhs, RHS &&rhs) {
> + RET sum{};
> + bool b = __builtin_sub_overflow(lhs, rhs, &sum);
> + return {b, sum};
> +}
> +
> +static_assert(sub<unsigned char>(static_cast<char>(0),static_cast<char>(1))
> == Result<unsigned char>{true, UCHAR_MAX});
> +static_assert(sub<char>(static_cast<unsigned
> char>(0),static_cast<unsigned char>(1)) == Result<char>{false, -1});
> +static_assert(sub<unsigned
> short>(static_cast<short>(0),static_cast<short>(1))
> == Result<unsigned short>{true, USHRT_MAX});
> +
> +static_assert(sub<int>(17,22) == Result<int>{false, -5});
> +static_assert(sub<int>(INT_MAX - 22, -23) == Result<int>{true, INT_MIN});
> +static_assert(sub<int>(INT_MIN + 22, 23) == Result<int>{true, INT_MAX});
> +
> +template <typename RET, typename LHS, typename RHS>
> +constexpr Result<RET> mul(LHS &&lhs, RHS &&rhs) {
> + RET sum{};
> + bool b = __builtin_mul_overflow(lhs, rhs, &sum);
> + return {b, sum};
> +}
> +
> +static_assert(mul<int>(17,22) == Result<int>{false, 374});
> +static_assert(mul<int>(INT_MAX / 22, 23) == Result<int>{true,
> -2049870757});
> +static_assert(mul<int>(INT_MIN / 22, -23) == Result<int>{true,
> -2049870757});
> +
> +constexpr Result<int> sadd(int lhs, int rhs) {
> + int sum{};
> + bool b = __builtin_sadd_overflow(lhs, rhs, &sum);
> + return {b, sum};
> +}
> +
> +static_assert(sadd(17,22) == Result<int>{false, 39});
> +static_assert(sadd(INT_MAX - 22, 23) == Result<int>{true, INT_MIN});
> +static_assert(sadd(INT_MIN + 22, -23) == Result<int>{true, INT_MAX});
> +
> +constexpr Result<int> ssub(int lhs, int rhs) {
> + int sum{};
> + bool b = __builtin_ssub_overflow(lhs, rhs, &sum);
> + return {b, sum};
> +}
> +
> +static_assert(ssub(17,22) == Result<int>{false, -5});
> +static_assert(ssub(INT_MAX - 22, -23) == Result<int>{true, INT_MIN});
> +static_assert(ssub(INT_MIN + 22, 23) == Result<int>{true, INT_MAX});
> +
> +constexpr Result<int> smul(int lhs, int rhs) {
> + int sum{};
> + bool b = __builtin_smul_overflow(lhs, rhs, &sum);
> + return {b, sum};
> +}
> +
> +static_assert(smul(17,22) == Result<int>{false, 374});
> +static_assert(smul(INT_MAX / 22, 23) == Result<int>{true, -2049870757});
> +static_assert(smul(INT_MIN / 22, -23) == Result<int>{true, -2049870757});
>
>
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