Author: Karl-Johan Karlsson Date: 2023-10-25T09:48:01+02:00 New Revision: d25e0aac415f45ce98c3700010acb5a98f016cef
URL: https://github.com/llvm/llvm-project/commit/d25e0aac415f45ce98c3700010acb5a98f016cef DIFF: https://github.com/llvm/llvm-project/commit/d25e0aac415f45ce98c3700010acb5a98f016cef.diff LOG: [Sema] Fixed faulty shift count warning (#69521) Constant values of _BitInt have the bitwith to exactly fit the constant number. This patch fix a problem in Sema when building an APInt where the supplied bitwidth can become too small and simply truncate the value leading to a faulty warning. Added: Modified: clang/docs/ReleaseNotes.rst clang/lib/Sema/SemaExpr.cpp clang/test/Sema/c2x-expr-range.c Removed: ################################################################################ diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index a063733e96cb74c..4cc148905d4e130 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -488,6 +488,9 @@ Bug Fixes in This Version - Clang no longer permits using the `_BitInt` types as an underlying type for an enumeration as specified in the C23 Standard. Fixes (`#69619 <https://github.com/llvm/llvm-project/issues/69619>`_) +- Fixed an issue when a shift count specified by a small constant ``_BitInt()``, + in a left shift operation, could result in a faulty warnings about + ``shift count >= width of type``. - Clang now accepts anonymous members initialized with designated initializers inside templates. Fixes (`#65143 <https://github.com/llvm/llvm-project/issues/65143>`_) diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp index 895b22805860d98..c2772bfb71c77e9 100644 --- a/clang/lib/Sema/SemaExpr.cpp +++ b/clang/lib/Sema/SemaExpr.cpp @@ -12143,8 +12143,7 @@ static void DiagnoseBadShiftValues(Sema& S, ExprResult &LHS, ExprResult &RHS, auto FXSema = S.Context.getFixedPointSemantics(LHSExprType); LeftSize = FXSema.getWidth() - (unsigned)FXSema.hasUnsignedPadding(); } - llvm::APInt LeftBits(Right.getBitWidth(), LeftSize); - if (Right.uge(LeftBits)) { + if (Right.uge(LeftSize)) { S.DiagRuntimeBehavior(Loc, RHS.get(), S.PDiag(diag::warn_shift_gt_typewidth) << RHS.get()->getSourceRange()); @@ -12186,7 +12185,7 @@ static void DiagnoseBadShiftValues(Sema& S, ExprResult &LHS, ExprResult &RHS, llvm::APInt ResultBits = static_cast<llvm::APInt &>(Right) + Left.getSignificantBits(); - if (LeftBits.uge(ResultBits)) + if (ResultBits.ule(LeftSize)) return; llvm::APSInt Result = Left.extend(ResultBits.getLimitedValue()); Result = Result.shl(Right); @@ -12200,7 +12199,7 @@ static void DiagnoseBadShiftValues(Sema& S, ExprResult &LHS, ExprResult &RHS, // bugs -- if the result is cast back to an unsigned type, it will have the // expected value. Thus we place this behind a diff erent warning that can be // turned off separately if needed. - if (LeftBits == ResultBits - 1) { + if (ResultBits - 1 == LeftSize) { S.Diag(Loc, diag::warn_shift_result_sets_sign_bit) << HexResult << LHSType << LHS.get()->getSourceRange() << RHS.get()->getSourceRange(); diff --git a/clang/test/Sema/c2x-expr-range.c b/clang/test/Sema/c2x-expr-range.c index 73683e6bfe684aa..eff0b7cd4d9f546 100644 --- a/clang/test/Sema/c2x-expr-range.c +++ b/clang/test/Sema/c2x-expr-range.c @@ -12,3 +12,15 @@ void test1(int *a) { void test2(__uint128_t *a) { (void)(*a >> ((__uint128_t)__UINT64_MAX__ + 1) <= 0); // expected-warning {{shift count >= width of type}} } + +// Regression test for bug where a faulty warning was given. We don't expect to +// see any warning in this case. +_BitInt(128) test3(_BitInt(128) a) { + return a << 12wb; +} + +// Similar to test3 above, but with a too large shift count. We expect to see a +// warning in this case. +_BitInt(128) test4(_BitInt(128) a) { + return a << 129wb; // expected-warning {{shift count >= width of type}} +} _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits