https://github.com/hax0kartik updated https://github.com/llvm/llvm-project/pull/176390
>From d293e4acd557a0361a5d02ce88d81e42283c694a Mon Sep 17 00:00:00 2001 From: hax0kartik <[email protected]> Date: Fri, 16 Jan 2026 19:37:54 +0530 Subject: [PATCH] [clang][bytecode] Handle corner condition for sign negation RHS = -RHS works for most cases, however, the behaviour when RHS is INTXX_MIN is undefined. In these particular case(s), we should use INTXX_MAX instead. --- clang/lib/AST/ByteCode/Interp.h | 4 +++- clang/test/AST/ByteCode/shifts.cpp | 2 ++ 2 files changed, 5 insertions(+), 1 deletion(-) diff --git a/clang/lib/AST/ByteCode/Interp.h b/clang/lib/AST/ByteCode/Interp.h index 7700b6bc5f2dd..0eae7848b4fe0 100644 --- a/clang/lib/AST/ByteCode/Interp.h +++ b/clang/lib/AST/ByteCode/Interp.h @@ -2888,7 +2888,9 @@ inline bool DoShift(InterpState &S, CodePtr OpPC, LT &LHS, RT &RHS, S.CCEDiag(Loc, diag::note_constexpr_negative_shift) << RHS.toAPSInt(); if (!S.noteUndefinedBehavior()) return false; - RHS = -RHS; + + RHS = RHS.isMin() ? RT(APSInt::getMaxValue(RHS.bitWidth(), false)) : -RHS; + return DoShift<LT, RT, Dir == ShiftDir::Left ? ShiftDir::Right : ShiftDir::Left>( S, OpPC, LHS, RHS, Result); diff --git a/clang/test/AST/ByteCode/shifts.cpp b/clang/test/AST/ByteCode/shifts.cpp index f02aaf004cbd6..58118bbea7941 100644 --- a/clang/test/AST/ByteCode/shifts.cpp +++ b/clang/test/AST/ByteCode/shifts.cpp @@ -75,6 +75,8 @@ namespace shifts { // ref-cxx17-warning {{shift count >= width of type}} (void)((long)c << __CHAR_BIT__); + c = 1 << (int)INT_MIN; // all-warning {{shift count is negative}} + int i; // cxx17-warning {{uninitialized variable}} \ // ref-cxx17-warning {{uninitialized variable}} i = 1 << (__INT_WIDTH__ - 2); _______________________________________________ cfe-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
