From: Jakub Jelinek Date: Fri, 20 Nov 2020 11:28:34 +0000 (+0100) Subject: c++: Add __builtin_clear_padding builtin - C++20 P0528R3 compiler side [PR88101] X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=1bea0d0aa5936cb36b6f86f721ca03c1a1bb601d;p=gcc.git c++: Add __builtin_clear_padding builtin - C++20 P0528R3 compiler side [PR88101] The following patch implements __builtin_clear_padding builtin that clears the padding bits in object representation (but preserves value representation). Inside of unions it clears only those padding bits that are padding for all the union members (so that it never alters value representation). It handles trailing padding, padding in the middle of structs including bitfields (PDP11 unhandled, I've never figured out how those bitfields work), VLAs (doesn't handle variable length structures, but I think almost nobody uses them and it isn't worth the extra complexity). For VLAs and sufficiently large arrays it uses runtime clearing loop instead of emitting straight-line code (unless arrays are inside of a union). The way I think this can be used for atomics is e.g. if the structures are power of two sized and small enough that we use the hw atomics for say compare_exchange __builtin_clear_padding could be called first on the address of expected and desired arguments (for desired only if we want to ensure that most of the time the atomic memory will have padding bits cleared), then perform the weak cmpxchg and if that fails, we got the value from the atomic memory; we can call __builtin_clear_padding on a copy of that and then compare it with expected, and if it is the same with the padding bits masked off, we can use the original with whatever random padding bits in it as the new expected for next cmpxchg. __builtin_clear_padding itself is not atomic and therefore it shouldn't be called on the atomic memory itself, but compare_exchange*'s expected argument is a reference and normally the implementation may store there the current value from memory, so padding bits can be cleared in that, and desired is passed by value rather than reference, so clearing is fine too. When using libatomic, we can use it either that way, or add new libatomic APIs that accept another argument, pointer to the padding bit bitmask, and construct that in the template as alignas (_T) unsigned char _mask[sizeof (_T)]; std::memset (_mask, ~0, sizeof (_mask)); __builtin_clear_padding ((_T *) _mask); which will have bits cleared for padding bits and set for bits taking part in the value representation. Then libatomic could internally instead of using memcmp compare for (i = 0; i < N; i++) if ((val1[i] & mask[i]) != (val2[i] & mask[i])) 2020-11-20 Jakub Jelinek PR libstdc++/88101 gcc/ * builtins.def (BUILT_IN_CLEAR_PADDING): New built-in function. * gimplify.c (gimplify_call_expr): Rewrite single argument BUILT_IN_CLEAR_PADDING into two-argument variant. * gimple-fold.c (clear_padding_unit, clear_padding_buf_size): New const variables. (struct clear_padding_struct): New type. (clear_padding_flush, clear_padding_add_padding, clear_padding_emit_loop, clear_padding_type, clear_padding_union, clear_padding_real_needs_padding_p, clear_padding_type_may_have_padding_p, gimple_fold_builtin_clear_padding): New functions. (gimple_fold_builtin): Handle BUILT_IN_CLEAR_PADDING. * doc/extend.texi (__builtin_clear_padding): Document. gcc/c-family/ * c-common.c (check_builtin_function_arguments): Handle BUILT_IN_CLEAR_PADDING. gcc/testsuite/ * c-c++-common/builtin-clear-padding-1.c: New test. * c-c++-common/torture/builtin-clear-padding-1.c: New test. * c-c++-common/torture/builtin-clear-padding-2.c: New test. * c-c++-common/torture/builtin-clear-padding-3.c: New test. * c-c++-common/torture/builtin-clear-padding-4.c: New test. * c-c++-common/torture/builtin-clear-padding-5.c: New test. * g++.dg/torture/builtin-clear-padding-1.C: New test. * g++.dg/torture/builtin-clear-padding-2.C: New test. * gcc.dg/builtin-clear-padding-1.c: New test. --- diff --git a/gcc/builtins.def b/gcc/builtins.def index b4494c712a1..04dbe790943 100644 --- a/gcc/builtins.def +++ b/gcc/builtins.def @@ -839,6 +839,7 @@ DEF_EXT_LIB_BUILTIN (BUILT_IN_CLEAR_CACHE, "__clear_cache", BT_FN_VOID_PTR_PT /* [trans-mem]: Adjust BUILT_IN_TM_CALLOC if BUILT_IN_CALLOC is changed. */ DEF_LIB_BUILTIN (BUILT_IN_CALLOC, "calloc", BT_FN_PTR_SIZE_SIZE, ATTR_MALLOC_WARN_UNUSED_RESULT_SIZE_1_2_NOTHROW_LEAF_LIST) DEF_GCC_BUILTIN (BUILT_IN_CLASSIFY_TYPE, "classify_type", BT_FN_INT_VAR, ATTR_LEAF_LIST) +DEF_GCC_BUILTIN (BUILT_IN_CLEAR_PADDING, "clear_padding", BT_FN_VOID_VAR, ATTR_NOTHROW_NONNULL_TYPEGENERIC_LEAF) DEF_GCC_BUILTIN (BUILT_IN_CLZ, "clz", BT_FN_INT_UINT, ATTR_CONST_NOTHROW_LEAF_LIST) DEF_GCC_BUILTIN (BUILT_IN_CLZIMAX, "clzimax", BT_FN_INT_UINTMAX, ATTR_CONST_NOTHROW_LEAF_LIST) DEF_GCC_BUILTIN (BUILT_IN_CLZL, "clzl", BT_FN_INT_ULONG, ATTR_CONST_NOTHROW_LEAF_LIST) diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c index 729bd85960f..5d1e4ef289c 100644 --- a/gcc/c-family/c-common.c +++ b/gcc/c-family/c-common.c @@ -6178,6 +6178,39 @@ check_builtin_function_arguments (location_t loc, vec arg_loc, } return false; + case BUILT_IN_CLEAR_PADDING: + if (builtin_function_validate_nargs (loc, fndecl, nargs, 1)) + { + if (!POINTER_TYPE_P (TREE_TYPE (args[0]))) + { + error_at (ARG_LOCATION (0), "argument %u in call to function " + "%qE does not have pointer type", 1, fndecl); + return false; + } + else if (!COMPLETE_TYPE_P (TREE_TYPE (TREE_TYPE (args[0])))) + { + error_at (ARG_LOCATION (0), "argument %u in call to function " + "%qE points to incomplete type", 1, fndecl); + return false; + } + else if (TYPE_READONLY (TREE_TYPE (TREE_TYPE (args[0])))) + { + error_at (ARG_LOCATION (0), "argument %u in call to function %qE " + "has pointer to %qs type (%qT)", 1, fndecl, "const", + TREE_TYPE (args[0])); + return false; + } + else if (TYPE_ATOMIC (TREE_TYPE (TREE_TYPE (args[0])))) + { + error_at (ARG_LOCATION (0), "argument %u in call to function %qE " + "has pointer to %qs type (%qT)", 1, fndecl, + "_Atomic", TREE_TYPE (args[0])); + return false; + } + return true; + } + return false; + default: return true; } diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi index cdf9108cd5b..f0269422ca2 100644 --- a/gcc/doc/extend.texi +++ b/gcc/doc/extend.texi @@ -13564,6 +13564,19 @@ initializers of variables usable in constant expressions. For more details refer to the latest revision of the C++ standard. @end deftypefn +@deftypefn {Built-in Function} void __builtin_clear_padding (@var{ptr}) +The built-in function @code{__builtin_clear_padding} function clears +padding bits inside of the object representation of object pointed by +@var{ptr}, which has to be a pointer. The value representation of the +object is not affected. The type of the object is assumed to be the type +the pointer points to. Inside of a union, the only cleared bits are +bits that are padding bits for all the union members. + +This built-in-function is useful if the padding bits of an object might +have intederminate values and the object representation needs to be +bitwise compared to some other object, for example for atomic operations. +@end deftypefn + @deftypefn {Built-in Function} long __builtin_expect (long @var{exp}, long @var{c}) @opindex fprofile-arcs You may use @code{__builtin_expect} to provide the compiler with diff --git a/gcc/gimple-fold.c b/gcc/gimple-fold.c index ca38a31c3c2..5d60bef285a 100644 --- a/gcc/gimple-fold.c +++ b/gcc/gimple-fold.c @@ -3948,6 +3948,698 @@ gimple_fold_builtin_realloc (gimple_stmt_iterator *gsi) return false; } +/* Number of bytes into which any type but aggregate or vector types + should fit. */ +static constexpr size_t clear_padding_unit + = MAX_BITSIZE_MODE_ANY_MODE / BITS_PER_UNIT; +/* Buffer size on which __builtin_clear_padding folding code works. */ +static const size_t clear_padding_buf_size = 32 * clear_padding_unit; + +/* Data passed through __builtin_clear_padding folding. */ +struct clear_padding_struct { + location_t loc; + tree base; + tree alias_type; + gimple_stmt_iterator *gsi; + /* Alignment of buf->base + 0. */ + unsigned align; + /* Offset from buf->base. Should be always a multiple of UNITS_PER_WORD. */ + HOST_WIDE_INT off; + /* Number of padding bytes before buf->off that don't have padding clear + code emitted yet. */ + HOST_WIDE_INT padding_bytes; + /* The size of the whole object. Never emit code to touch + buf->base + buf->sz or following bytes. */ + HOST_WIDE_INT sz; + /* Number of bytes recorded in buf->buf. */ + size_t size; + /* When inside union, instead of emitting code we and bits inside of + the union_ptr array. */ + unsigned char *union_ptr; + /* Set bits mean padding bits that need to be cleared by the builtin. */ + unsigned char buf[clear_padding_buf_size + clear_padding_unit]; +}; + +/* Emit code to clear padding requested in BUF->buf - set bits + in there stand for padding that should be cleared. FULL is true + if everything from the buffer should be flushed, otherwise + it can leave up to 2 * clear_padding_unit bytes for further + processing. */ + +static void +clear_padding_flush (clear_padding_struct *buf, bool full) +{ + gcc_assert ((clear_padding_unit % UNITS_PER_WORD) == 0); + if (!full && buf->size < 2 * clear_padding_unit) + return; + gcc_assert ((buf->off % UNITS_PER_WORD) == 0); + size_t end = buf->size; + if (!full) + end = ((end - clear_padding_unit - 1) / clear_padding_unit + * clear_padding_unit); + size_t padding_bytes = buf->padding_bytes; + if (buf->union_ptr) + { + /* Inside of a union, instead of emitting any code, instead + clear all bits in the union_ptr buffer that are clear + in buf. Whole padding bytes don't clear anything. */ + for (size_t i = 0; i < end; i++) + { + if (buf->buf[i] == (unsigned char) ~0) + padding_bytes++; + else + { + padding_bytes = 0; + buf->union_ptr[buf->off + i] &= buf->buf[i]; + } + } + if (full) + { + buf->off = 0; + buf->size = 0; + buf->padding_bytes = 0; + } + else + { + memmove (buf->buf, buf->buf + end, buf->size - end); + buf->off += end; + buf->size -= end; + buf->padding_bytes = padding_bytes; + } + return; + } + size_t wordsize = UNITS_PER_WORD; + for (size_t i = 0; i < end; i += wordsize) + { + size_t nonzero_first = wordsize; + size_t nonzero_last = 0; + bool all_ones = true; + if ((unsigned HOST_WIDE_INT) (buf->off + i + wordsize) + > (unsigned HOST_WIDE_INT) buf->sz) + { + gcc_assert (wordsize > 1); + wordsize /= 2; + i -= wordsize; + continue; + } + for (size_t j = i; j < i + wordsize && j < end; j++) + { + if (buf->buf[j]) + { + if (nonzero_first == wordsize) + { + nonzero_first = j - i; + nonzero_last = j - i; + } + if (nonzero_last != j - i) + all_ones = false; + nonzero_last = j + 1 - i; + } + if (buf->buf[j] != 0 && buf->buf[j] != (unsigned char) ~0) + all_ones = false; + } + if (padding_bytes) + { + if (nonzero_first == 0 + && nonzero_last == wordsize + && all_ones) + { + /* All bits are padding and we had some padding + before too. Just extend it. */ + padding_bytes += wordsize; + continue; + } + size_t padding_end = i; + if (all_ones && nonzero_first == 0) + { + padding_bytes += nonzero_last; + padding_end += nonzero_last; + nonzero_first = wordsize; + nonzero_last = 0; + } + tree atype = build_array_type_nelts (char_type_node, padding_bytes); + tree dst = build2_loc (buf->loc, MEM_REF, atype, buf->base, + build_int_cst (buf->alias_type, + buf->off + padding_end + - padding_bytes)); + tree src = build_constructor (atype, NULL); + gimple *g = gimple_build_assign (dst, src); + gimple_set_location (g, buf->loc); + gsi_insert_before (buf->gsi, g, GSI_SAME_STMT); + padding_bytes = 0; + buf->padding_bytes = 0; + } + if (nonzero_first == wordsize) + /* All bits in a word are 0, there are no padding bits. */ + continue; + if (all_ones && nonzero_last == wordsize) + { + /* All bits between nonzero_first and end of word are padding + bits, start counting padding_bytes. */ + padding_bytes = nonzero_last - nonzero_first; + continue; + } + for (size_t eltsz = 1; eltsz <= wordsize; eltsz <<= 1) + { + if (nonzero_last - nonzero_first <= eltsz + && ((nonzero_first & ~(eltsz - 1)) + == ((nonzero_last - 1) & ~(eltsz - 1)))) + { + tree type; + if (eltsz == 1) + type = char_type_node; + else + type = lang_hooks.types.type_for_size (eltsz * BITS_PER_UNIT, + 0); + size_t start = nonzero_first & ~(eltsz - 1); + HOST_WIDE_INT off = buf->off + i + start; + tree atype = type; + if (eltsz > 1 && buf->align < TYPE_ALIGN (type)) + atype = build_aligned_type (type, buf->align); + tree dst = build2_loc (buf->loc, MEM_REF, atype, buf->base, + build_int_cst (buf->alias_type, off)); + tree src; + gimple *g; + if (all_ones + && nonzero_first == start + && nonzero_last == start + eltsz) + src = build_zero_cst (type); + else + { + src = make_ssa_name (type); + g = gimple_build_assign (src, unshare_expr (dst)); + gimple_set_location (g, buf->loc); + gsi_insert_before (buf->gsi, g, GSI_SAME_STMT); + tree mask = native_interpret_expr (type, + buf->buf + i + start, + eltsz); + gcc_assert (mask && TREE_CODE (mask) == INTEGER_CST); + mask = fold_build1 (BIT_NOT_EXPR, type, mask); + tree src_masked = make_ssa_name (type); + g = gimple_build_assign (src_masked, BIT_AND_EXPR, + src, mask); + gimple_set_location (g, buf->loc); + gsi_insert_before (buf->gsi, g, GSI_SAME_STMT); + src = src_masked; + } + g = gimple_build_assign (dst, src); + gimple_set_location (g, buf->loc); + gsi_insert_before (buf->gsi, g, GSI_SAME_STMT); + break; + } + } + } + if (full) + { + if (padding_bytes) + { + tree atype = build_array_type_nelts (char_type_node, padding_bytes); + tree dst = build2_loc (buf->loc, MEM_REF, atype, buf->base, + build_int_cst (buf->alias_type, + buf->off + end + - padding_bytes)); + tree src = build_constructor (atype, NULL); + gimple *g = gimple_build_assign (dst, src); + gimple_set_location (g, buf->loc); + gsi_insert_before (buf->gsi, g, GSI_SAME_STMT); + } + size_t end_rem = end % UNITS_PER_WORD; + buf->off += end - end_rem; + buf->size = end_rem; + memset (buf->buf, 0, buf->size); + buf->padding_bytes = 0; + } + else + { + memmove (buf->buf, buf->buf + end, buf->size - end); + buf->off += end; + buf->size -= end; + buf->padding_bytes = padding_bytes; + } +} + +/* Append PADDING_BYTES padding bytes. */ + +static void +clear_padding_add_padding (clear_padding_struct *buf, + HOST_WIDE_INT padding_bytes) +{ + if (padding_bytes == 0) + return; + if ((unsigned HOST_WIDE_INT) padding_bytes + buf->size + > (unsigned HOST_WIDE_INT) clear_padding_buf_size) + clear_padding_flush (buf, false); + if ((unsigned HOST_WIDE_INT) padding_bytes + buf->size + > (unsigned HOST_WIDE_INT) clear_padding_buf_size) + { + memset (buf->buf + buf->size, ~0, clear_padding_buf_size - buf->size); + padding_bytes -= clear_padding_buf_size - buf->size; + buf->size = clear_padding_buf_size; + clear_padding_flush (buf, false); + gcc_assert (buf->padding_bytes); + /* At this point buf->buf[0] through buf->buf[buf->size - 1] + is guaranteed to be all ones. */ + padding_bytes += buf->size; + buf->size = padding_bytes % UNITS_PER_WORD; + memset (buf->buf, ~0, buf->size); + buf->off += padding_bytes - buf->size; + buf->padding_bytes += padding_bytes - buf->size; + } + else + { + memset (buf->buf + buf->size, ~0, padding_bytes); + buf->size += padding_bytes; + } +} + +static void clear_padding_type (clear_padding_struct *, tree, HOST_WIDE_INT); + +/* Clear padding bits of union type TYPE. */ + +static void +clear_padding_union (clear_padding_struct *buf, tree type, HOST_WIDE_INT sz) +{ + clear_padding_struct *union_buf; + HOST_WIDE_INT start_off = 0, next_off = 0; + size_t start_size = 0; + if (buf->union_ptr) + { + start_off = buf->off + buf->size; + next_off = start_off + sz; + start_size = start_off % UNITS_PER_WORD; + start_off -= start_size; + clear_padding_flush (buf, true); + union_buf = buf; + } + else + { + if (sz + buf->size > clear_padding_buf_size) + clear_padding_flush (buf, false); + union_buf = XALLOCA (clear_padding_struct); + union_buf->loc = buf->loc; + union_buf->base = NULL_TREE; + union_buf->alias_type = NULL_TREE; + union_buf->gsi = NULL; + union_buf->align = 0; + union_buf->off = 0; + union_buf->padding_bytes = 0; + union_buf->sz = sz; + union_buf->size = 0; + if (sz + buf->size <= clear_padding_buf_size) + union_buf->union_ptr = buf->buf + buf->size; + else + union_buf->union_ptr = XNEWVEC (unsigned char, sz); + memset (union_buf->union_ptr, ~0, sz); + } + + for (tree field = TYPE_FIELDS (type); field; field = DECL_CHAIN (field)) + if (TREE_CODE (field) == FIELD_DECL) + { + HOST_WIDE_INT fldsz = tree_to_shwi (DECL_SIZE_UNIT (field)); + gcc_assert (union_buf->size == 0); + union_buf->off = start_off; + union_buf->size = start_size; + memset (union_buf->buf, ~0, start_size); + clear_padding_type (union_buf, TREE_TYPE (field), fldsz); + clear_padding_add_padding (union_buf, sz - fldsz); + clear_padding_flush (union_buf, true); + } + + if (buf == union_buf) + { + buf->off = next_off; + buf->size = next_off % UNITS_PER_WORD; + buf->off -= buf->size; + memset (buf->buf, ~0, buf->size); + } + else if (sz + buf->size <= clear_padding_buf_size) + buf->size += sz; + else + { + unsigned char *union_ptr = union_buf->union_ptr; + while (sz) + { + clear_padding_flush (buf, false); + HOST_WIDE_INT this_sz + = MIN ((unsigned HOST_WIDE_INT) sz, + clear_padding_buf_size - buf->size); + memcpy (buf->buf + buf->size, union_ptr, this_sz); + buf->size += this_sz; + union_ptr += this_sz; + sz -= this_sz; + } + XDELETE (union_buf->union_ptr); + } +} + +/* The only known floating point formats with padding bits are the + IEEE extended ones. */ + +static bool +clear_padding_real_needs_padding_p (tree type) +{ + const struct real_format *fmt = REAL_MODE_FORMAT (TYPE_MODE (type)); + return (fmt->b == 2 + && fmt->signbit_ro == fmt->signbit_rw + && (fmt->signbit_ro == 79 || fmt->signbit_ro == 95)); +} + +/* Return true if TYPE might contain any padding bits. */ + +static bool +clear_padding_type_may_have_padding_p (tree type) +{ + switch (TREE_CODE (type)) + { + case RECORD_TYPE: + case UNION_TYPE: + return true; + case ARRAY_TYPE: + case COMPLEX_TYPE: + case VECTOR_TYPE: + return clear_padding_type_may_have_padding_p (TREE_TYPE (type)); + case REAL_TYPE: + return clear_padding_real_needs_padding_p (type); + default: + return false; + } +} + +/* Emit a runtime loop: + for (; buf.base != end; buf.base += sz) + __builtin_clear_padding (buf.base); */ + +static void +clear_padding_emit_loop (clear_padding_struct *buf, tree type, tree end) +{ + tree l1 = create_artificial_label (buf->loc); + tree l2 = create_artificial_label (buf->loc); + tree l3 = create_artificial_label (buf->loc); + gimple *g = gimple_build_goto (l2); + gimple_set_location (g, buf->loc); + gsi_insert_before (buf->gsi, g, GSI_SAME_STMT); + g = gimple_build_label (l1); + gimple_set_location (g, buf->loc); + gsi_insert_before (buf->gsi, g, GSI_SAME_STMT); + clear_padding_type (buf, type, buf->sz); + clear_padding_flush (buf, true); + g = gimple_build_assign (buf->base, POINTER_PLUS_EXPR, buf->base, + size_int (buf->sz)); + gimple_set_location (g, buf->loc); + gsi_insert_before (buf->gsi, g, GSI_SAME_STMT); + g = gimple_build_label (l2); + gimple_set_location (g, buf->loc); + gsi_insert_before (buf->gsi, g, GSI_SAME_STMT); + g = gimple_build_cond (NE_EXPR, buf->base, end, l1, l3); + gimple_set_location (g, buf->loc); + gsi_insert_before (buf->gsi, g, GSI_SAME_STMT); + g = gimple_build_label (l3); + gimple_set_location (g, buf->loc); + gsi_insert_before (buf->gsi, g, GSI_SAME_STMT); +} + +/* Clear padding bits for TYPE. Called recursively from + gimple_fold_builtin_clear_padding. */ + +static void +clear_padding_type (clear_padding_struct *buf, tree type, HOST_WIDE_INT sz) +{ + switch (TREE_CODE (type)) + { + case RECORD_TYPE: + HOST_WIDE_INT cur_pos; + cur_pos = 0; + for (tree field = TYPE_FIELDS (type); field; field = DECL_CHAIN (field)) + if (TREE_CODE (field) == FIELD_DECL) + { + if (DECL_BIT_FIELD (field)) + { + if (DECL_NAME (field) == NULL_TREE) + continue; + HOST_WIDE_INT fldsz = TYPE_PRECISION (TREE_TYPE (field)); + if (fldsz == 0) + continue; + HOST_WIDE_INT pos = int_byte_position (field); + HOST_WIDE_INT bpos + = tree_to_uhwi (DECL_FIELD_BIT_OFFSET (field)); + bpos %= BITS_PER_UNIT; + HOST_WIDE_INT end + = ROUND_UP (bpos + fldsz, BITS_PER_UNIT) / BITS_PER_UNIT; + if (pos + end > cur_pos) + { + clear_padding_add_padding (buf, pos + end - cur_pos); + cur_pos = pos + end; + } + gcc_assert (cur_pos > pos + && ((unsigned HOST_WIDE_INT) buf->size + >= (unsigned HOST_WIDE_INT) cur_pos - pos)); + unsigned char *p = buf->buf + buf->size - (cur_pos - pos); + if (BYTES_BIG_ENDIAN != WORDS_BIG_ENDIAN) + sorry_at (buf->loc, "PDP11 bit-field handling unsupported" + " in %qs", "__builtin_clear_padding"); + else if (BYTES_BIG_ENDIAN) + { + /* Big endian. */ + if (bpos + fldsz <= BITS_PER_UNIT) + *p &= ~(((1 << fldsz) - 1) + << (BITS_PER_UNIT - bpos - fldsz)); + else + { + if (bpos) + { + *p &= ~(((1U << BITS_PER_UNIT) - 1) >> bpos); + p++; + fldsz -= BITS_PER_UNIT - bpos; + } + memset (p, 0, fldsz / BITS_PER_UNIT); + p += fldsz / BITS_PER_UNIT; + fldsz %= BITS_PER_UNIT; + if (fldsz) + *p &= ((1U << BITS_PER_UNIT) - 1) >> fldsz; + } + } + else + { + /* Little endian. */ + if (bpos + fldsz <= BITS_PER_UNIT) + *p &= ~(((1 << fldsz) - 1) << bpos); + else + { + if (bpos) + { + *p &= ~(((1 << BITS_PER_UNIT) - 1) << bpos); + p++; + fldsz -= BITS_PER_UNIT - bpos; + } + memset (p, 0, fldsz / BITS_PER_UNIT); + p += fldsz / BITS_PER_UNIT; + fldsz %= BITS_PER_UNIT; + if (fldsz) + *p &= ~((1 << fldsz) - 1); + } + } + } + else + { + HOST_WIDE_INT pos = int_byte_position (field); + HOST_WIDE_INT fldsz = tree_to_shwi (DECL_SIZE_UNIT (field)); + gcc_assert (pos >= 0 && fldsz >= 0 && pos >= cur_pos); + clear_padding_add_padding (buf, pos - cur_pos); + cur_pos = pos; + clear_padding_type (buf, TREE_TYPE (field), fldsz); + cur_pos += fldsz; + } + } + gcc_assert (sz >= cur_pos); + clear_padding_add_padding (buf, sz - cur_pos); + break; + case ARRAY_TYPE: + HOST_WIDE_INT nelts, fldsz; + fldsz = int_size_in_bytes (TREE_TYPE (type)); + nelts = sz / fldsz; + if (nelts > 1 + && sz > 8 * UNITS_PER_WORD + && buf->union_ptr == NULL + && clear_padding_type_may_have_padding_p (TREE_TYPE (type))) + { + /* For sufficiently large array of more than one elements, + emit a runtime loop to keep code size manageable. */ + tree base = buf->base; + unsigned int prev_align = buf->align; + HOST_WIDE_INT off = buf->off + buf->size; + HOST_WIDE_INT prev_sz = buf->sz; + clear_padding_flush (buf, true); + tree elttype = TREE_TYPE (type); + buf->base = create_tmp_var (build_pointer_type (elttype)); + tree end = make_ssa_name (TREE_TYPE (buf->base)); + gimple *g = gimple_build_assign (buf->base, POINTER_PLUS_EXPR, + base, size_int (off)); + gimple_set_location (g, buf->loc); + gsi_insert_before (buf->gsi, g, GSI_SAME_STMT); + g = gimple_build_assign (end, POINTER_PLUS_EXPR, buf->base, + size_int (sz)); + gimple_set_location (g, buf->loc); + gsi_insert_before (buf->gsi, g, GSI_SAME_STMT); + buf->sz = fldsz; + buf->align = TYPE_ALIGN (elttype); + buf->off = 0; + buf->size = 0; + clear_padding_emit_loop (buf, elttype, end); + buf->base = base; + buf->sz = prev_sz; + buf->align = prev_align; + buf->size = off % UNITS_PER_WORD; + buf->off = off - buf->size; + memset (buf->buf, 0, buf->size); + break; + } + for (HOST_WIDE_INT i = 0; i < nelts; i++) + clear_padding_type (buf, TREE_TYPE (type), fldsz); + break; + case UNION_TYPE: + clear_padding_union (buf, type, sz); + break; + case REAL_TYPE: + gcc_assert ((size_t) sz <= clear_padding_unit); + if ((unsigned HOST_WIDE_INT) sz + buf->size > clear_padding_buf_size) + clear_padding_flush (buf, false); + if (clear_padding_real_needs_padding_p (type)) + { + /* Use native_interpret_expr + native_encode_expr to figure out + which bits are padding. */ + memset (buf->buf + buf->size, ~0, sz); + tree cst = native_interpret_expr (type, buf->buf + buf->size, sz); + gcc_assert (cst && TREE_CODE (cst) == REAL_CST); + int len = native_encode_expr (cst, buf->buf + buf->size, sz); + gcc_assert (len > 0 && (size_t) len == (size_t) sz); + for (size_t i = 0; i < (size_t) sz; i++) + buf->buf[buf->size + i] ^= ~0; + } + else + memset (buf->buf + buf->size, 0, sz); + buf->size += sz; + break; + case COMPLEX_TYPE: + fldsz = int_size_in_bytes (TREE_TYPE (type)); + clear_padding_type (buf, TREE_TYPE (type), fldsz); + clear_padding_type (buf, TREE_TYPE (type), fldsz); + break; + case VECTOR_TYPE: + nelts = TYPE_VECTOR_SUBPARTS (type).to_constant (); + fldsz = int_size_in_bytes (TREE_TYPE (type)); + for (HOST_WIDE_INT i = 0; i < nelts; i++) + clear_padding_type (buf, TREE_TYPE (type), fldsz); + break; + case NULLPTR_TYPE: + gcc_assert ((size_t) sz <= clear_padding_unit); + if ((unsigned HOST_WIDE_INT) sz + buf->size > clear_padding_buf_size) + clear_padding_flush (buf, false); + memset (buf->buf + buf->size, ~0, sz); + buf->size += sz; + break; + default: + gcc_assert ((size_t) sz <= clear_padding_unit); + if ((unsigned HOST_WIDE_INT) sz + buf->size > clear_padding_buf_size) + clear_padding_flush (buf, false); + memset (buf->buf + buf->size, 0, sz); + buf->size += sz; + break; + } +} + +/* Fold __builtin_clear_padding builtin. */ + +static bool +gimple_fold_builtin_clear_padding (gimple_stmt_iterator *gsi) +{ + gimple *stmt = gsi_stmt (*gsi); + gcc_assert (gimple_call_num_args (stmt) == 2); + tree ptr = gimple_call_arg (stmt, 0); + tree typearg = gimple_call_arg (stmt, 1); + tree type = TREE_TYPE (TREE_TYPE (typearg)); + location_t loc = gimple_location (stmt); + clear_padding_struct buf; + gimple_stmt_iterator gsiprev = *gsi; + /* This should be folded during the lower pass. */ + gcc_assert (!gimple_in_ssa_p (cfun) && cfun->cfg == NULL); + gcc_assert (COMPLETE_TYPE_P (type)); + gsi_prev (&gsiprev); + + buf.loc = loc; + buf.base = ptr; + buf.alias_type = NULL_TREE; + buf.gsi = gsi; + buf.align = get_pointer_alignment (ptr); + unsigned int talign = min_align_of_type (type) * BITS_PER_UNIT; + buf.align = MAX (buf.align, talign); + buf.off = 0; + buf.padding_bytes = 0; + buf.size = 0; + buf.sz = int_size_in_bytes (type); + buf.union_ptr = NULL; + if (buf.sz < 0 && int_size_in_bytes (strip_array_types (type)) < 0) + sorry_at (loc, "%s not supported for variable length aggregates", + "__builtin_clear_padding"); + /* The implementation currently assumes 8-bit host and target + chars which is the case for all currently supported targets + and hosts and is required e.g. for native_{encode,interpret}* APIs. */ + else if (CHAR_BIT != 8 || BITS_PER_UNIT != 8) + sorry_at (loc, "%s not supported on this target", + "__builtin_clear_padding"); + else if (!clear_padding_type_may_have_padding_p (type)) + ; + else if (TREE_CODE (type) == ARRAY_TYPE && buf.sz < 0) + { + tree sz = TYPE_SIZE_UNIT (type); + tree elttype = type; + /* Only supports C/C++ VLAs and flattens all the VLA levels. */ + while (TREE_CODE (elttype) == ARRAY_TYPE + && int_size_in_bytes (elttype) < 0) + elttype = TREE_TYPE (elttype); + HOST_WIDE_INT eltsz = int_size_in_bytes (elttype); + gcc_assert (eltsz >= 0); + if (eltsz) + { + buf.base = create_tmp_var (build_pointer_type (elttype)); + tree end = make_ssa_name (TREE_TYPE (buf.base)); + gimple *g = gimple_build_assign (buf.base, ptr); + gimple_set_location (g, loc); + gsi_insert_before (gsi, g, GSI_SAME_STMT); + g = gimple_build_assign (end, POINTER_PLUS_EXPR, buf.base, sz); + gimple_set_location (g, loc); + gsi_insert_before (gsi, g, GSI_SAME_STMT); + buf.sz = eltsz; + buf.align = TYPE_ALIGN (elttype); + buf.alias_type = build_pointer_type (elttype); + clear_padding_emit_loop (&buf, elttype, end); + } + } + else + { + if (!is_gimple_mem_ref_addr (buf.base)) + { + buf.base = make_ssa_name (TREE_TYPE (ptr)); + gimple *g = gimple_build_assign (buf.base, ptr); + gimple_set_location (g, loc); + gsi_insert_before (gsi, g, GSI_SAME_STMT); + } + buf.alias_type = build_pointer_type (type); + clear_padding_type (&buf, type, buf.sz); + clear_padding_flush (&buf, true); + } + + gimple_stmt_iterator gsiprev2 = *gsi; + gsi_prev (&gsiprev2); + if (gsi_stmt (gsiprev) == gsi_stmt (gsiprev2)) + gsi_replace (gsi, gimple_build_nop (), true); + else + { + gsi_remove (gsi, true); + *gsi = gsiprev2; + } + return true; +} + /* Fold the non-target builtin at *GSI and return whether any simplification was made. */ @@ -4105,6 +4797,9 @@ gimple_fold_builtin (gimple_stmt_iterator *gsi) case BUILT_IN_REALLOC: return gimple_fold_builtin_realloc (gsi); + case BUILT_IN_CLEAR_PADDING: + return gimple_fold_builtin_clear_padding (gsi); + default:; } diff --git a/gcc/gimplify.c b/gcc/gimplify.c index fd0b5202b45..53ec9ecdb64 100644 --- a/gcc/gimplify.c +++ b/gcc/gimplify.c @@ -3384,6 +3384,20 @@ gimplify_call_expr (tree *expr_p, gimple_seq *pre_p, bool want_value) cfun->calls_eh_return = true; break; + case BUILT_IN_CLEAR_PADDING: + if (call_expr_nargs (*expr_p) == 1) + { + /* Remember the original type of the argument in an internal + dummy second argument, as in GIMPLE pointer conversions are + useless. */ + p = CALL_EXPR_ARG (*expr_p, 0); + *expr_p + = build_call_expr_loc (EXPR_LOCATION (*expr_p), fndecl, 2, p, + build_zero_cst (TREE_TYPE (p))); + return GS_OK; + } + break; + default: ; } diff --git a/gcc/testsuite/c-c++-common/builtin-clear-padding-1.c b/gcc/testsuite/c-c++-common/builtin-clear-padding-1.c new file mode 100644 index 00000000000..8b036bf405e --- /dev/null +++ b/gcc/testsuite/c-c++-common/builtin-clear-padding-1.c @@ -0,0 +1,19 @@ +/* PR libstdc++/88101 */ +/* { dg-do compile } */ + +struct S; +struct T { char a; long long b; }; + +void +foo (struct S *p, void *q, char *r, const struct T *s) +{ + __builtin_clear_padding (); /* { dg-error "too few arguments to function '__builtin_clear_padding'" } */ + __builtin_clear_padding (1); /* { dg-error "argument 1 in call to function '__builtin_clear_padding' does not have pointer type" } */ + __builtin_clear_padding (&p); + __builtin_clear_padding (&p, 1); /* { dg-error "too many arguments to function '__builtin_clear_padding'" } */ + __builtin_clear_padding (&p, &p); /* { dg-error "too many arguments to function '__builtin_clear_padding'" } */ + __builtin_clear_padding (p); /* { dg-error "argument 1 in call to function '__builtin_clear_padding' points to incomplete type" } */ + __builtin_clear_padding (q); /* { dg-error "argument 1 in call to function '__builtin_clear_padding' points to incomplete type" } */ + __builtin_clear_padding (r); + __builtin_clear_padding (s); /* { dg-error "argument 1 in call to function '__builtin_clear_padding' has pointer to 'const' type" } */ +} diff --git a/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-1.c b/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-1.c new file mode 100644 index 00000000000..6b01a5614b5 --- /dev/null +++ b/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-1.c @@ -0,0 +1,47 @@ +/* PR libstdc++/88101 */ + +int i1, i2; +long double l1, l2; +struct S { char a; short b; char c; int d; char e; long long f; char g; long double h; } s1, s2; +struct T { int a; struct S b[3]; int c; } t1, t2; +struct U { int a : 3; int : 2; int b : 15; int : 14; int c : 1; int : 0; int : 3; int d : 2; int : 3; int e : 13; int : 3; signed char f; } u1, u2; + +__attribute__((noipa)) void +foo (int *i, long double *l, struct S *s, struct T *t, struct U *u) +{ + *i = 123; + *l = -123.456L; + s->a = 1; s->b = 2; s->c = 3; s->d = 4; s->e = 5; s->f = 6; s->g = 7; s->h = 18.52L; + t->a = 8; t->c = 9; + t->b[0].a = 11; t->b[0].b = 12; t->b[0].c = 13; t->b[0].d = 14; + t->b[0].e = 15; t->b[0].f = 16; t->b[0].g = 17; t->b[0].h = 18.26L; + t->b[1].a = 21; t->b[1].b = 22; t->b[1].c = 23; t->b[1].d = 24; + t->b[1].e = 25; t->b[1].f = 26; t->b[1].g = 27; t->b[1].h = 28.26L; + t->b[2].a = 31; t->b[2].b = 32; t->b[2].c = 33; t->b[2].d = 34; + t->b[2].e = 35; t->b[2].f = 36; t->b[2].g = 37; t->b[2].h = 38.26L; + u->a = -1; u->b = -1; u->c = -1; u->d = -1; u->e = -1; u->f = -1; +} + +int +main () +{ + __builtin_memset (&i2, -1, sizeof (i2)); + __builtin_memset (&l2, -1, sizeof (i2)); + __builtin_memset (&s2, -1, sizeof (s2)); + __builtin_memset (&t2, -1, sizeof (t2)); + __builtin_memset (&u2, -1, sizeof (u2)); + foo (&i1, &l1, &s1, &t1, &u1); + foo (&i2, &l2, &s2, &t2, &u2); + __builtin_clear_padding (&i2); + __builtin_clear_padding (&l2); + __builtin_clear_padding (&s2); + __builtin_clear_padding (&t2); + __builtin_clear_padding (&u2); + if (__builtin_memcmp (&i1, &i2, sizeof (i1)) + || __builtin_memcmp (&l1, &l2, sizeof (l1)) + || __builtin_memcmp (&s1, &s2, sizeof (s1)) + || __builtin_memcmp (&t1, &t2, sizeof (t1)) + || __builtin_memcmp (&u1, &u2, sizeof (u1))) + __builtin_abort (); + return 0; +} diff --git a/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-2.c b/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-2.c new file mode 100644 index 00000000000..1188bc07ed2 --- /dev/null +++ b/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-2.c @@ -0,0 +1,24 @@ +/* PR libstdc++/88101 */ + +typedef int T __attribute__((aligned (16384))); +struct S { char a; short b; long double c; T d; T e; long long f; }; + +__attribute__((noipa)) void +foo (struct S *s) +{ + s->a = -1; s->b = -1; s->c = -18.52L; s->d = -1; s->e = -1; s->f = -1; +} + +int +main () +{ + struct S s1, s2; + __builtin_memset (&s1, 0, sizeof (s1)); + __builtin_memset (&s2, -1, sizeof (s2)); + foo (&s1); + foo (&s2); + __builtin_clear_padding (&s2); + if (__builtin_memcmp (&s1, &s2, sizeof (s1))) + __builtin_abort (); + return 0; +} diff --git a/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-3.c b/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-3.c new file mode 100644 index 00000000000..edb7c8eb555 --- /dev/null +++ b/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-3.c @@ -0,0 +1,65 @@ +/* PR libstdc++/88101 */ + +union V { char a; signed char b; unsigned char c; }; +struct T { char a; int b; union V c; }; +union U { int a; long double b; struct T c; }; +struct S { char a; union U b; long long c; char d; } s1, s2; + +__attribute__((noipa)) void +foo (struct S *s, int x) +{ + s->a = -1; s->c = -1; s->d = -1; + switch (x) + { + case 0: + s->b.a = -1; + break; + case 1: + s->b.b = -12345.25L; + break; + case 2: + s->b.c.a = -1; + s->b.c.b = -1; + s->b.c.c.b = -1; + break; + } +} + +int +main () +{ + __builtin_memset (&s1, 0, sizeof (s1)); + __builtin_memset (&s2, -1, sizeof (s2)); + foo (&s1, 0); + foo (&s2, 0); + __builtin_clear_padding (&s2); + if (s2.b.a != (char) -1) + __builtin_abort (); + __builtin_clear_padding (&s2.b.a); + __builtin_memset (&s2.b.a + 1, 0, sizeof (union U) - sizeof (s2.b.a)); + if (__builtin_memcmp (&s1, &s2, sizeof (s1))) + __builtin_abort (); + __builtin_memset (&s1, 0, sizeof (s1)); + __builtin_memset (&s2, -1, sizeof (s2)); + foo (&s1, 1); + foo (&s2, 1); + __builtin_clear_padding (&s2); + if (s2.b.b != -12345.25L) + __builtin_abort (); + __builtin_clear_padding (&s2.b.b); + __builtin_memset (&s2.b.b + 1, 0, sizeof (union U) - sizeof (s2.b.b)); + if (__builtin_memcmp (&s1, &s2, sizeof (s1))) + __builtin_abort (); + __builtin_memset (&s1, 0, sizeof (s1)); + __builtin_memset (&s2, -1, sizeof (s2)); + foo (&s1, 2); + foo (&s2, 2); + __builtin_clear_padding (&s2); + if (s2.b.c.a != (char) -1 || s2.b.c.b != -1 || s2.b.c.c.b != -1) + __builtin_abort (); + __builtin_clear_padding (&s2.b.c); + __builtin_memset (&s2.b.c + 1, 0, sizeof (union U) - sizeof (s2.b.c)); + if (__builtin_memcmp (&s1, &s2, sizeof (s1))) + __builtin_abort (); + return 0; +} diff --git a/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-4.c b/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-4.c new file mode 100644 index 00000000000..d24f3b59d7b --- /dev/null +++ b/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-4.c @@ -0,0 +1,59 @@ +/* PR libstdc++/88101 */ + +struct S { char a; short b; char c; }; + +__attribute__((noipa)) void +foo (int m, int n, int o) +{ + long double a1[m]; + long double a2[m]; + struct S b1[m][n]; + struct S b2[m][n]; + struct S c1[m][n][o]; + struct S c2[m][n][o]; + int i, j, k; + __builtin_memset (&a1, 0, sizeof (a1)); + __builtin_memset (&a2, ~0, sizeof (a2)); + __builtin_memset (&b1, 0, sizeof (b1)); + __builtin_memset (&b2, ~0, sizeof (b2)); + __builtin_memset (&c1, 0, sizeof (c1)); + __builtin_memset (&c2, ~0, sizeof (c2)); + for (i = 0; i < m; i++) + { + a1[i] = 13.132L; + a2[i] = 13.132L; + for (j = 0; j < n; j++) + { + b1[i][j].a = -1; + b1[i][j].b = -1; + b1[i][j].c = -1; + b2[i][j].a = -1; + b2[i][j].b = -1; + b2[i][j].c = -1; + for (k = 0; k < o; k++) + { + c1[i][j][k].a = -1; + c1[i][j][k].b = -1; + c1[i][j][k].c = -1; + c2[i][j][k].a = -1; + c2[i][j][k].b = -1; + c2[i][j][k].c = -1; + } + } + } + __builtin_clear_padding (&a2); + __builtin_clear_padding (&b2); + __builtin_clear_padding (&c2); + if (__builtin_memcmp (&a1, &a2, sizeof (a1)) + || __builtin_memcmp (&b1, &b2, sizeof (b1)) + || __builtin_memcmp (&c1, &c2, sizeof (c1))) + __builtin_abort (); +} + +int +main () +{ + foo (5, 3, 4); + foo (17, 2, 1); + return 0; +} diff --git a/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-5.c b/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-5.c new file mode 100644 index 00000000000..d5dbafe1c74 --- /dev/null +++ b/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-5.c @@ -0,0 +1,49 @@ +/* PR libstdc++/88101 */ + +struct S { char a; short b; char c; } s1[24], s2[24]; +struct T { char a; long long b; char c; struct S d[3]; long long e; char f; } t1, t2; +struct U { char a; long long b; char c; struct S d[25]; long long e; char f; } u1, u2; + +__attribute__((noipa)) void +foo (struct S *s, struct T *t, struct U *u) +{ + int i; + t->a = -1; t->b = -1; t->c = -1; t->e = -1; t->f = -1; + u->a = -1; u->b = -1; u->c = -1; u->e = -1; u->f = -1; + for (i = 0; i < 24; i++) + { + s[i].a = -1; + s[i].b = -1; + s[i].c = -1; + } + for (i = 0; i < 3; i++) + { + t->d[i].a = -1; + t->d[i].b = -1; + t->d[i].c = -1; + } + for (i = 0; i < 25; i++) + { + u->d[i].a = -1; + u->d[i].b = -1; + u->d[i].c = -1; + } +} + +int +main () +{ + __builtin_memset (&s2, -1, sizeof (s2)); + __builtin_memset (&t2, -1, sizeof (t2)); + __builtin_memset (&u2, -1, sizeof (u2)); + foo (&s1[0], &t1, &u1); + foo (&s2[0], &t2, &u2); + __builtin_clear_padding (&s2); + __builtin_clear_padding (&t2); + __builtin_clear_padding (&u2); + if (__builtin_memcmp (&s1, &s2, sizeof (s1)) + || __builtin_memcmp (&t1, &t2, sizeof (t1)) + || __builtin_memcmp (&u1, &u2, sizeof (u1))) + __builtin_abort (); + return 0; +} diff --git a/gcc/testsuite/g++.dg/torture/builtin-clear-padding-1.C b/gcc/testsuite/g++.dg/torture/builtin-clear-padding-1.C new file mode 100644 index 00000000000..625a047ab1c --- /dev/null +++ b/gcc/testsuite/g++.dg/torture/builtin-clear-padding-1.C @@ -0,0 +1,31 @@ +/* PR libstdc++/88101 */ + +struct S {} s1, s2; +struct T : public S { char a; short b; char c; } t1, t2; +struct U : public T { char d; long long e; char f; } u1, u2; + +__attribute__((noipa)) void +foo (T *t, U *u) +{ + int i; + t->a = -1; t->b = -1; t->c = -1; + u->a = -1; u->b = -1; u->c = -1; u->d = -1; u->e = -1; u->f = -1; +} + +int +main () +{ + __builtin_memset (&s2, -1, sizeof (s2)); + __builtin_memset (&t2, -1, sizeof (t2)); + __builtin_memset (&u2, -1, sizeof (u2)); + foo (&t1, &u1); + foo (&t2, &u2); + __builtin_clear_padding (&s2); + __builtin_clear_padding (&t2); + __builtin_clear_padding (&u2); + if (__builtin_memcmp (&s1, &s2, sizeof (s1)) + || __builtin_memcmp (&t1, &t2, sizeof (t1)) + || __builtin_memcmp (&u1, &u2, sizeof (u1))) + __builtin_abort (); + return 0; +} diff --git a/gcc/testsuite/g++.dg/torture/builtin-clear-padding-2.C b/gcc/testsuite/g++.dg/torture/builtin-clear-padding-2.C new file mode 100644 index 00000000000..19cc78f6610 --- /dev/null +++ b/gcc/testsuite/g++.dg/torture/builtin-clear-padding-2.C @@ -0,0 +1,34 @@ +/* PR libstdc++/88101 */ + +#include + +struct S { char a; short b; char c; long long d; char e; decltype (nullptr) f; char g; }; +alignas (S) unsigned char buf1[sizeof (S)]; +alignas (S) unsigned char buf2[sizeof (S)]; + +template +void +foo () +{ + __builtin_clear_padding ((S *) buf2); +} + +void +bar (S *s) +{ + s->a = -1; s->b = -1; s->c = -1; s->d = -1; s->e = -1; s->g = -1; +} + +int +main () +{ + S *s1 = new (buf1) S; + S *s2 = new (buf2) S; + __builtin_memset (s1, 0, sizeof (S)); + __builtin_memset (s2, ~0, sizeof (S)); + bar (s1); + bar (s2); + foo <0> (); + if (__builtin_memcmp (s1, s2, sizeof (S)) != 0) + __builtin_abort (); +} diff --git a/gcc/testsuite/gcc.dg/builtin-clear-padding-1.c b/gcc/testsuite/gcc.dg/builtin-clear-padding-1.c new file mode 100644 index 00000000000..27ffc0a57ce --- /dev/null +++ b/gcc/testsuite/gcc.dg/builtin-clear-padding-1.c @@ -0,0 +1,10 @@ +/* PR libstdc++/88101 */ +/* { dg-do compile } */ +/* { dg-options "" } */ + +void +foo (int n) +{ + struct S { char a; int b[n]; long long c; } s; + __builtin_clear_padding (&s); /* { dg-message "unimplemented: __builtin_clear_padding not supported for variable length aggregates" } */ +}