Summary:
This makes it consistent with `memcmp` and `__builtin_bcmp`.
Also see the discussion in https://reviews.llvm.org/D56593.
Reviewers: jyknight
Subscribers: kristina, cfe-commits
Tags: #clang
Differential Revision: https://reviews.llvm.org/D58120
llvm-svn: 354023
Summary:
`memchr` and `memcmp` operate upon the character units of the object
representation; that is, the `size_t` parameter expresses the number of
character units. The constant folding implementation is updated in this
patch to account for multibyte element types in the arrays passed to
`memchr`/`memcmp` and, in the case of `memcmp`, to account for the
possibility that the arrays may have differing element types (even when
they are byte-sized).
Actual inspection of the object representation is not implemented.
Comparisons are done only between elements with the same object size;
that is, `memchr` will fail when inspecting at least one character unit
of a multibyte element. The integer types are assumed to have two's
complement representation with 0 for `false`, 1 for `true`, and no
padding bits.
`memcmp` on multibyte elements will only be able to fold in cases where
enough elements are equal for the answer to be 0.
Various tests are added to guard against incorrect folding for cases
that miscompile on some system or other prior to this patch. At the same
time, the unsigned 32-bit `wchar_t` testing in
`test/SemaCXX/constexpr-string.cpp` is restored.
Reviewers: rsmith, aaron.ballman, hfinkel
Reviewed By: rsmith
Subscribers: cfe-commits
Differential Revision: https://reviews.llvm.org/D55510
llvm-svn: 348938
Fix code for constant evaluation of __builtin_memcpy() and
__builtin_memmove() that would attempt to divide by zero when given two
pointers to an incomplete array.
Differential Revision: https://reviews.llvm.org/D51855
llvm-svn: 343761
__builtin_memmove (in non-type-punning cases).
This is intended to permit libc++ to make std::copy etc constexpr
without sacrificing the optimization that uses memcpy on
trivially-copyable types.
__builtin_strcpy and __builtin_wcscpy are not handled by this change.
They'd be straightforward to add, but we haven't encountered a need for
them just yet.
This reinstates r338455, reverted in r338602, with a fix to avoid trying
to constant-evaluate a memcpy call if either pointer operand has an
invalid designator.
llvm-svn: 338941
It caused asserts during Chromium builds, see reply on the cfe-commits thread.
> This is intended to permit libc++ to make std::copy etc constexpr
> without sacrificing the optimization that uses memcpy on
> trivially-copyable types.
>
> __builtin_strcpy and __builtin_wcscpy are not handled by this change.
> They'd be straightforward to add, but we haven't encountered a need for
> them just yet.
llvm-svn: 338602
__builtin_memmove (in non-type-punning cases).
This is intended to permit libc++ to make std::copy etc constexpr
without sacrificing the optimization that uses memcpy on
trivially-copyable types.
__builtin_strcpy and __builtin_wcscpy are not handled by this change.
They'd be straightforward to add, but we haven't encountered a need for
them just yet.
llvm-svn: 338455
This makes it return the right result in a couple of edge cases. The
wide versions always do the comparison on the underlying wchar_t type.
llvm-svn: 330656
by providing a memchr builtin that returns char* instead of void*.
Also add a __has_feature flag to indicate the presence of constexpr forms of
the relevant <string> functions.
llvm-svn: 292555
Clement Courbet