Author: Tommy Chiang Date: 2026-03-07T02:06:03+08:00 New Revision: d4efbf10f183657c85bfed31b747f3d8f493ab31
URL: https://github.com/llvm/llvm-project/commit/d4efbf10f183657c85bfed31b747f3d8f493ab31 DIFF: https://github.com/llvm/llvm-project/commit/d4efbf10f183657c85bfed31b747f3d8f493ab31.diff LOG: [Clang][ExprConst] Handle APValue::LValue in BitCast (#184865) Instead of marking the branch unreachable, emit an unsupported type diagnostic and return false when encountering `APValue::LValue` in `APValueToBufferConverter`. A good example of this is: ``` long fn() { return __builtin_bit_cast(long, (long)&fn); } ``` Although `&fn` itself is a pointer type, the cast `(long)` converts it to an integer type, which passes `checkBitCastConstexprEligibilityType`. Thus, eventually, we see it in Converter, which does not expect an LValue. Fixes https://github.com/llvm/llvm-project/issues/44991 Added: clang/test/CodeGen/bitcast-based-lvalue.c Modified: clang/lib/AST/ExprConstant.cpp Removed: ################################################################################ diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp index 43409fd2af82e..429fef0a1afa8 100644 --- a/clang/lib/AST/ExprConstant.cpp +++ b/clang/lib/AST/ExprConstant.cpp @@ -7776,6 +7776,7 @@ class APValueToBufferConverter { case APValue::FixedPoint: // FIXME: We should support these. + case APValue::LValue: case APValue::Matrix: case APValue::Union: case APValue::MemberPointer: @@ -7785,9 +7786,6 @@ class APValueToBufferConverter { << Ty; return false; } - - case APValue::LValue: - llvm_unreachable("LValue subobject in bit_cast?"); } llvm_unreachable("Unhandled APValue::ValueKind"); } diff --git a/clang/test/CodeGen/bitcast-based-lvalue.c b/clang/test/CodeGen/bitcast-based-lvalue.c new file mode 100644 index 0000000000000..af64c6fe97ce9 --- /dev/null +++ b/clang/test/CodeGen/bitcast-based-lvalue.c @@ -0,0 +1,7 @@ +// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -emit-llvm -o - %s | FileCheck %s + +long fn(void) { return __builtin_bit_cast(long, (long)&fn); } + +// CHECK-LABEL: define{{.*}} i64 @fn() +// CHECK: store i64 ptrtoint (ptr @fn to i64), ptr %ref.tmp, align 8 +// CHECK: ret i64 %{{.*}} _______________________________________________ cfe-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
