Author: Daniel Bertalan Date: 2022-05-10T16:02:23+01:00 New Revision: 93a8225da1f983cccb3e4b5e762369121aaa7dd5
URL: https://github.com/llvm/llvm-project/commit/93a8225da1f983cccb3e4b5e762369121aaa7dd5 DIFF: https://github.com/llvm/llvm-project/commit/93a8225da1f983cccb3e4b5e762369121aaa7dd5.diff LOG: [CodeGen] Use ABI alignment for C++ new expressions In case of placement new, if we do not know the alignment of the operand, we can't assume it has the preferred alignment. It might be e.g. a pointer to a struct member which follows ABI alignment rules. This makes UBSAN no longer report "constructor call on misaligned address" when constructing a double into a struct field of type double on i686. The psABI specifies an alignment of 4 bytes, but the preferred alignment used by Clang is 8 bytes. We now use ABI alignment for allocating new as well, as the preferred alignment should be used for over-aligning e.g. local variables, which isn't relevant for ABI code dealing with operator new. AFAICT there wouldn't be problems either way though. Fixes #54845. Differential Revision: https://reviews.llvm.org/D124736 Added: clang/test/CodeGenCXX/pr54845.cpp Modified: clang/lib/CodeGen/CGExprCXX.cpp Removed: ################################################################################ diff --git a/clang/lib/CodeGen/CGExprCXX.cpp b/clang/lib/CodeGen/CGExprCXX.cpp index 54c87a7361b1c..3cc1443615420 100644 --- a/clang/lib/CodeGen/CGExprCXX.cpp +++ b/clang/lib/CodeGen/CGExprCXX.cpp @@ -1573,7 +1573,7 @@ llvm::Value *CodeGenFunction::EmitCXXNewExpr(const CXXNewExpr *E) { llvm::Value *allocSize = EmitCXXNewAllocSize(*this, E, minElements, numElements, allocSizeWithoutCookie); - CharUnits allocAlign = getContext().getPreferredTypeAlignInChars(allocType); + CharUnits allocAlign = getContext().getTypeAlignInChars(allocType); // Emit the allocation call. If the allocator is a global placement // operator, just "inline" it directly. diff --git a/clang/test/CodeGenCXX/pr54845.cpp b/clang/test/CodeGenCXX/pr54845.cpp new file mode 100644 index 0000000000000..acf2c3121900b --- /dev/null +++ b/clang/test/CodeGenCXX/pr54845.cpp @@ -0,0 +1,12 @@ +// RUN: %clang_cc1 -triple i686-linux-gnu -emit-llvm %s -o - | FileCheck %s +// https://github.com/llvm/llvm-project/issues/54845 + +void *operator new(unsigned int, void *); + +void test(double *d) { + // This store used to have an alignment of 8, which was incorrect as + // the i386 psABI only guarantees a 4-byte alignment for doubles. + + // CHECK: store double 0.000000e+00, {{.*}}, align 4 + new (d) double(0); +} _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
