Author: erichkeane Date: Thu May 30 14:35:32 2019 New Revision: 362157 URL: http://llvm.org/viewvc/llvm-project?rev=362157&view=rev Log: Fix constexpr __builtin_*_overflow issue when unsigned->signed operand.
As reported here https://bugs.llvm.org/show_bug.cgi?id=42000, it was possible to get the constexpr version of __builtin_*_overflow to give the wrong answer. This was because when extending the operands to fit the largest type (so that the math could be done), the decision on whether to sign/zero extend the operands was based on the result signedness, not on the operands signedness. In the reported case, (unsigned char)255 - (int)100 needed to have each extended to the int in order to do the math. However, when extending the first operand to 'int', we incorrectly sign extended it instead of zero extending. Thus, the result didnt fit back into the unsigned char. The fix for this was simply to choose zero/sign extension based on the sign of the operand itself. Differential Revision: https://reviews.llvm.org/D62665 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=362157&r1=362156&r2=362157&view=diff ============================================================================== --- cfe/trunk/lib/AST/ExprConstant.cpp (original) +++ cfe/trunk/lib/AST/ExprConstant.cpp Thu May 30 14:35:32 2019 @@ -9454,10 +9454,8 @@ bool IntExprEvaluator::VisitBuiltinCallE if (IsSigned && !AllSigned) ++MaxBits; - LHS = APSInt(IsSigned ? LHS.sextOrSelf(MaxBits) : LHS.zextOrSelf(MaxBits), - !IsSigned); - RHS = APSInt(IsSigned ? RHS.sextOrSelf(MaxBits) : RHS.zextOrSelf(MaxBits), - !IsSigned); + LHS = APSInt(LHS.extOrTrunc(MaxBits), !IsSigned); + RHS = APSInt(RHS.extOrTrunc(MaxBits), !IsSigned); Result = APSInt(MaxBits, !IsSigned); } Modified: cfe/trunk/test/SemaCXX/builtins-overflow.cpp URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/builtins-overflow.cpp?rev=362157&r1=362156&r2=362157&view=diff ============================================================================== --- cfe/trunk/test/SemaCXX/builtins-overflow.cpp (original) +++ cfe/trunk/test/SemaCXX/builtins-overflow.cpp Thu May 30 14:35:32 2019 @@ -2,6 +2,7 @@ // expected-no-diagnostics #include <limits.h> +#include <stdint.h> int a() { const int x = 3; @@ -50,6 +51,7 @@ constexpr Result<RET> sub(LHS &&lhs, RHS 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<uint8_t>(static_cast<uint8_t>(255),static_cast<int>(100)) == Result<uint8_t>{false, 155}); static_assert(sub<int>(17,22) == Result<int>{false, -5}); static_assert(sub<int>(INT_MAX - 22, -23) == Result<int>{true, INT_MIN}); @@ -91,3 +93,4 @@ constexpr Result<int> smul(int lhs, int 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}); + _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
