c: Don't drop vector attributes that affect type identity [PR98852]
<arm_neon.h> types are distinct from GNU vector types in at least their mangling. However, there used to be nothing explicit in the VECTOR_TYPE itself to indicate the difference: we simply treated them as distinct TYPE_MAIN_VARIANTs. This caused problems like the ones reported in PR95726. The fix for that PR was to add type attributes to the <arm_neon.h> types, in order to maintain the distinction between them and GNU vectors. However, this in turn caused PR98852, where c_common_type would unconditionally drop the attributes on the source types. This meant that: <arm_neon.h> vector + <arm_neon.h> vector had a GNU vector type rather than an <arm_neon.h> vector type. See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96377#c2 for Jakub's analysis of the history of this c_common_type code. TBH I'm not sure which case the build_type_attribute_variant code is handling, but I think we should at least avoid dropping attributes that affect type identity. I've tried to audit the C and target-specific attributes to look for other types that might be affected by this, but I couldn't see any. We are only dealing with: gcc_assert (code1 == VECTOR_TYPE || code1 == COMPLEX_TYPE || code1 == FIXED_POINT_TYPE || code1 == REAL_TYPE || code1 == INTEGER_TYPE); which excludes most affects_type_identity attributes. The closest was s390_vector_bool, but the handler for that attribute changes the type node and drops the attribute itself (*no_add_attrs = true). I put the main list handling into a separate function (remove_attributes_matching) because a later patch will need it for something else. gcc/ PR c/98852 * attribs.h (affects_type_identity_attributes): Declare. * attribs.c (remove_attributes_matching): New function. (affects_type_identity_attributes): Likewise. gcc/c/ PR c/98852 * c-typeck.c (c_common_type): Do not drop attributes that affect type identity. gcc/testsuite/ PR c/98852 * gcc.target/aarch64/advsimd-intrinsics/pr98852.c: New test.
This commit is contained in:
Richard Sandiford
parent
b5f644a98b
commit
a3317f7b3c
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@ -1366,6 +1366,60 @@ comp_type_attributes (const_tree type1, const_tree type2)
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return targetm.comp_type_attributes (type1, type2);
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}
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/* PREDICATE acts as a function of type:
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(const_tree attr, const attribute_spec *as) -> bool
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where ATTR is an attribute and AS is its possibly-null specification.
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Return a list of every attribute in attribute list ATTRS for which
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PREDICATE is true. Return ATTRS itself if PREDICATE returns true
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for every attribute. */
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template<typename Predicate>
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tree
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remove_attributes_matching (tree attrs, Predicate predicate)
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{
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tree new_attrs = NULL_TREE;
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tree *ptr = &new_attrs;
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const_tree start = attrs;
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for (const_tree attr = attrs; attr; attr = TREE_CHAIN (attr))
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{
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tree name = get_attribute_name (attr);
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const attribute_spec *as = lookup_attribute_spec (name);
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const_tree end;
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if (!predicate (attr, as))
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end = attr;
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else if (start == attrs)
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continue;
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else
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end = TREE_CHAIN (attr);
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for (; start != end; start = TREE_CHAIN (start))
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{
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*ptr = tree_cons (TREE_PURPOSE (start),
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TREE_VALUE (start), NULL_TREE);
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TREE_CHAIN (*ptr) = NULL_TREE;
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ptr = &TREE_CHAIN (*ptr);
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}
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start = TREE_CHAIN (attr);
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}
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gcc_assert (!start || start == attrs);
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return start ? attrs : new_attrs;
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}
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/* If VALUE is true, return the subset of ATTRS that affect type identity,
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otherwise return the subset of ATTRS that don't affect type identity. */
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tree
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affects_type_identity_attributes (tree attrs, bool value)
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{
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auto predicate = [value](const_tree, const attribute_spec *as) -> bool
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{
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return bool (as && as->affects_type_identity) == value;
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};
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return remove_attributes_matching (attrs, predicate);
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}
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/* Return a type like TTYPE except that its TYPE_ATTRIBUTE
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is ATTRIBUTE.
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@ -65,6 +65,8 @@ extern bool attribute_value_equal (const_tree, const_tree);
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warning to be generated). */
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extern int comp_type_attributes (const_tree, const_tree);
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extern tree affects_type_identity_attributes (tree, bool = true);
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/* Default versions of target-overridable functions. */
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extern tree merge_decl_attributes (tree, tree);
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extern tree merge_type_attributes (tree, tree);
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@ -740,10 +740,16 @@ c_common_type (tree t1, tree t2)
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t2 = TYPE_MAIN_VARIANT (t2);
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if (TYPE_ATTRIBUTES (t1) != NULL_TREE)
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t1 = build_type_attribute_variant (t1, NULL_TREE);
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{
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tree attrs = affects_type_identity_attributes (TYPE_ATTRIBUTES (t1));
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t1 = build_type_attribute_variant (t1, attrs);
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}
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if (TYPE_ATTRIBUTES (t2) != NULL_TREE)
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t2 = build_type_attribute_variant (t2, NULL_TREE);
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{
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tree attrs = affects_type_identity_attributes (TYPE_ATTRIBUTES (t2));
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t2 = build_type_attribute_variant (t2, attrs);
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}
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/* Save time if the two types are the same. */
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@ -0,0 +1,129 @@
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/* { dg-do compile } */
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/* { dg-additional-options "-std=c99" } */
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#include <arm_neon.h>
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typedef __typeof(((int32x4_t *) 0)[0][0]) int32_elt;
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typedef __typeof(((uint32x4_t *) 0)[0][0]) uint32_elt;
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typedef int32_elt gnu_int32x4_t __attribute__((vector_size(16)));
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typedef uint32_elt gnu_uint32x4_t __attribute__((vector_size(16)));
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#define X_gnu_int32x4_t 1
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#define X_gnu_uint32x4_t 2
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#define X_int32x4_t 3
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#define X_uint32x4_t 4
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#define CHECK(T) T: X_##T
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#define CHECK_TYPE(EXPR, TYPE) \
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do { \
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int x[_Generic (EXPR, \
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CHECK (gnu_int32x4_t), \
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CHECK (gnu_uint32x4_t), \
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CHECK (int32x4_t), \
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CHECK (uint32x4_t), \
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default : 0) == X_##TYPE ? 1 : -1]; \
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} while (0)
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void
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f (gnu_int32x4_t sg, gnu_uint32x4_t ug, int32x4_t sn, uint32x4_t un, int c)
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{
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CHECK_TYPE (sg, gnu_int32x4_t);
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CHECK_TYPE (ug, gnu_uint32x4_t);
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CHECK_TYPE (sn, int32x4_t);
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CHECK_TYPE (un, uint32x4_t);
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CHECK_TYPE (sg + 1, gnu_int32x4_t);
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CHECK_TYPE (ug + 1, gnu_uint32x4_t);
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CHECK_TYPE (sn + 1, int32x4_t);
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CHECK_TYPE (un + 1, uint32x4_t);
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CHECK_TYPE (1 + sg, gnu_int32x4_t);
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CHECK_TYPE (1 + ug, gnu_uint32x4_t);
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CHECK_TYPE (1 + sn, int32x4_t);
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CHECK_TYPE (1 + un, uint32x4_t);
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CHECK_TYPE (sg + sg, gnu_int32x4_t);
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CHECK_TYPE (ug + ug, gnu_uint32x4_t);
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CHECK_TYPE (sn + sn, int32x4_t);
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CHECK_TYPE (un + un, uint32x4_t);
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/* Traditional behavior for mixed signs is to pick the signedness of the
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first operand. We don't have any Arm-specific reason for preferring that
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behavior, but including the tests helps to demonstrate the points in the
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comments below. */
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CHECK_TYPE (sg + ug, gnu_int32x4_t);
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CHECK_TYPE (ug + sg, gnu_uint32x4_t);
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CHECK_TYPE (sn + un, int32x4_t);
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CHECK_TYPE (un + sn, uint32x4_t);
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/* Nothing specifies the type of mixed GNU and arm_neon.h operations, but:
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- it would be surprising if sg + un had a different signedness from
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sg + ug
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- it would also be mildly surprising if sg + un had a different type from
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both of its operands
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So in cases where the operands differ in both signedness and ABI, it seems
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more consistent to ignore the ABI difference and apply the usual rules for
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differences in sign. */
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CHECK_TYPE (sg + un, gnu_int32x4_t);
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CHECK_TYPE (ug + sn, gnu_uint32x4_t);
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CHECK_TYPE (sn + ug, int32x4_t);
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CHECK_TYPE (un + sg, uint32x4_t);
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/* And if the first vector wins when operands differ in both signedness
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and ABI, it seems more consistent to do the same if the operands differ
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only in ABI. */
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CHECK_TYPE (sg + sn, gnu_int32x4_t);
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CHECK_TYPE (ug + un, gnu_uint32x4_t);
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CHECK_TYPE (sn + sg, int32x4_t);
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CHECK_TYPE (un + ug, uint32x4_t);
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CHECK_TYPE (c ? sg + sg : sg, gnu_int32x4_t);
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CHECK_TYPE (c ? ug + ug : ug, gnu_uint32x4_t);
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CHECK_TYPE (c ? sn + sn : sn, int32x4_t);
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CHECK_TYPE (c ? un + un : un, uint32x4_t);
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CHECK_TYPE (c ? sg + 1 : sg, gnu_int32x4_t);
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CHECK_TYPE (c ? ug + 1 : ug, gnu_uint32x4_t);
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CHECK_TYPE (c ? sn + 1 : sn, int32x4_t);
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CHECK_TYPE (c ? un + 1 : un, uint32x4_t);
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CHECK_TYPE (c ? 1 + sg : sg, gnu_int32x4_t);
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CHECK_TYPE (c ? 1 + ug : ug, gnu_uint32x4_t);
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CHECK_TYPE (c ? 1 + sn : sn, int32x4_t);
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CHECK_TYPE (c ? 1 + un : un, uint32x4_t);
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CHECK_TYPE (c ? sg : sg + sg, gnu_int32x4_t);
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CHECK_TYPE (c ? ug : ug + ug, gnu_uint32x4_t);
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CHECK_TYPE (c ? sn : sn + sn, int32x4_t);
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CHECK_TYPE (c ? un : un + un, uint32x4_t);
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CHECK_TYPE (c ? sg : sg + 1, gnu_int32x4_t);
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CHECK_TYPE (c ? ug : ug + 1, gnu_uint32x4_t);
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CHECK_TYPE (c ? sn : sn + 1, int32x4_t);
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CHECK_TYPE (c ? un : un + 1, uint32x4_t);
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CHECK_TYPE (c ? sg : 1 + sg, gnu_int32x4_t);
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CHECK_TYPE (c ? ug : 1 + ug, gnu_uint32x4_t);
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CHECK_TYPE (c ? sn : 1 + sn, int32x4_t);
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CHECK_TYPE (c ? un : 1 + un, uint32x4_t);
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CHECK_TYPE (c ? sg + sg : sg + sg, gnu_int32x4_t);
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CHECK_TYPE (c ? ug + ug : ug + ug, gnu_uint32x4_t);
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CHECK_TYPE (c ? sn + sn : sn + sn, int32x4_t);
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CHECK_TYPE (c ? un + un : un + un, uint32x4_t);
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CHECK_TYPE (c ? sg + sg : sg + 1, gnu_int32x4_t);
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CHECK_TYPE (c ? ug + ug : ug + 1, gnu_uint32x4_t);
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CHECK_TYPE (c ? sn + sn : sn + 1, int32x4_t);
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CHECK_TYPE (c ? un + un : un + 1, uint32x4_t);
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CHECK_TYPE (c ? 1 + sg : sg + sg, gnu_int32x4_t);
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CHECK_TYPE (c ? 1 + ug : ug + ug, gnu_uint32x4_t);
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CHECK_TYPE (c ? 1 + sn : sn + sn, int32x4_t);
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CHECK_TYPE (c ? 1 + un : un + un, uint32x4_t);
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}
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