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author | Jakub Jelinek <jakub@redhat.com> | 2022-10-21 18:04:54 +0200 |
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committer | Jakub Jelinek <jakub@redhat.com> | 2022-10-21 18:04:54 +0200 |
commit | 2cc41601d9a948e8d612a21c3b9a44ce0b977747 (patch) | |
tree | 9ad44790376961af9de1d283b6edca8546cd5cc8 | |
parent | bf3b532b524ecacb3202ab2c8af419ffaaab7cff (diff) | |
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c++: Don't shortcut TREE_CONSTANT vector type CONSTRUCTORs in cxx_eval_constant_expression [PR107295]
The excess precision support broke building skia (dependency of firefox)
on ia32 (it has something like the a constexpr variable), but as the other
cases show, it is actually a preexisting problem if one uses casts from
constants with wider floating point types.
The problem is that cxx_eval_constant_expression tries to short-cut
processing of TREE_CONSTANT CONSTRUCTORs if they satisfy
reduced_constant_expression_p - instead of calling cxx_eval_bare_aggregate
on them it just verifies flags and if they are TREE_CONSTANT even after
that, just fold.
Now, on the testcase we have a TREE_CONSTANT CONSTRUCTOR containing
TREE_CONSTANT NOP_EXPR of REAL_CST. And, fold, which isn't recursive,
doesn't optimize that into VECTOR_CST, while later on we are only able
to optimize VECTOR_CST arithmetics, not arithmetics with vector
CONSTRUCTORs.
The following patch fixes that by rejecting CONSTRUCTORs with vector type
in reduced_constant_expression_p regardless of whether they have
CONSTRUCTOR_NO_CLEARING set or not, folding result in cxx_eval_bare_aggregate
even if nothing has changed but it wasn't non-constant and removing folding
from the TREE_CONSTANT reduced_constant_expression_p short-cut.
2022-10-21 Jakub Jelinek <jakub@redhat.com>
PR c++/107295
* constexpr.cc (reduced_constant_expression_p) <case CONSTRUCTOR>:
Return false for VECTOR_TYPE CONSTRUCTORs even without
CONSTRUCTOR_NO_CLEARING set on them.
(cxx_eval_bare_aggregate): If constant but !changed, fold before
returning VECTOR_TYPE_P CONSTRUCTOR.
(cxx_eval_constant_expression) <case CONSTRUCTOR>: Don't fold
TREE_CONSTANT CONSTRUCTOR, just return it.
* g++.dg/ext/vector42.C: New test.
-rw-r--r-- | gcc/cp/constexpr.cc | 21 | ||||
-rw-r--r-- | gcc/testsuite/g++.dg/ext/vector42.C | 12 |
2 files changed, 25 insertions, 8 deletions
diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc index 0366396..c3ee970 100644 --- a/gcc/cp/constexpr.cc +++ b/gcc/cp/constexpr.cc @@ -3104,12 +3104,12 @@ reduced_constant_expression_p (tree t) case CONSTRUCTOR: /* And we need to handle PTRMEM_CST wrapped in a CONSTRUCTOR. */ tree field; + if (TREE_CODE (TREE_TYPE (t)) == VECTOR_TYPE) + /* An initialized vector would have a VECTOR_CST. */ + return false; if (CONSTRUCTOR_NO_CLEARING (t)) { - if (TREE_CODE (TREE_TYPE (t)) == VECTOR_TYPE) - /* An initialized vector would have a VECTOR_CST. */ - return false; - else if (TREE_CODE (TREE_TYPE (t)) == ARRAY_TYPE) + if (TREE_CODE (TREE_TYPE (t)) == ARRAY_TYPE) { /* There must be a valid constant initializer at every array index. */ @@ -4956,8 +4956,14 @@ cxx_eval_bare_aggregate (const constexpr_ctx *ctx, tree t, TREE_SIDE_EFFECTS (ctx->ctor) = side_effects_p; } } - if (*non_constant_p || !changed) + if (*non_constant_p) return t; + if (!changed) + { + if (VECTOR_TYPE_P (type)) + t = fold (t); + return t; + } t = ctx->ctor; if (!t) t = build_constructor (type, NULL); @@ -7387,11 +7393,10 @@ cxx_eval_constant_expression (const constexpr_ctx *ctx, tree t, case CONSTRUCTOR: if (TREE_CONSTANT (t) && reduced_constant_expression_p (t)) { - /* Don't re-process a constant CONSTRUCTOR, but do fold it to - VECTOR_CST if applicable. */ + /* Don't re-process a constant CONSTRUCTOR. */ verify_constructor_flags (t); if (TREE_CONSTANT (t)) - return fold (t); + return t; } r = cxx_eval_bare_aggregate (ctx, t, lval, non_constant_p, overflow_p); diff --git a/gcc/testsuite/g++.dg/ext/vector42.C b/gcc/testsuite/g++.dg/ext/vector42.C new file mode 100644 index 0000000..e781097 --- /dev/null +++ b/gcc/testsuite/g++.dg/ext/vector42.C @@ -0,0 +1,12 @@ +// PR c++/107295 +// { dg-do compile { target c++11 } } + +template <typename T> struct A { + typedef T __attribute__((vector_size (sizeof (int)))) V; +}; +template <int, typename T> using B = typename A<T>::V; +template <typename T> using V = B<4, T>; +using F = V<float>; +constexpr F a = F () + 0.0f; +constexpr F b = F () + (float) 0.0; +constexpr F c = F () + (float) 0.0L; |