tree-optimization/105562 - avoid uninit diagnostic with better FRE
We can avoid some uninit diagnostics by making FRE disambiguate against CLOBBERs since any aliasing there would invoke undefined behavior for a read we are looking up. 2022-05-12 Richard Biener <rguenther@suse.de> PR tree-optimization/105562 * tree-ssa-sccvn.cc (vn_reference_lookup_3): Disambiguate against all CLOBBER defs if there's not an obvious must-alias and we are not doing redundant store elimination. (vn_walk_cb_data::redundant_store_removal_p): New field. (vn_reference_lookup_pieces): Initialize it. (vn_reference_lookup): Add argument to specify if we are doing redundant store removal. (eliminate_dom_walker::eliminate_stmt): Specify we do. * tree-ssa-sccvn.h (vn_reference_lookup): Adjust. * g++.dg/warn/uninit-pr105562.C: New testcase.
This commit is contained in:
Richard Biener
parent
78c8b0b980
commit
94b8a37fa1
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@ -0,0 +1,10 @@
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// { dg-require-effective-target c++11 }
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// { dg-options "-O -Wall -fno-strict-aliasing" }
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#include <regex>
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int main()
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{
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std::regex a(".");
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std::regex b(std::move(a));
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}
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@ -1799,11 +1799,13 @@ struct pd_data
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struct vn_walk_cb_data
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{
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vn_walk_cb_data (vn_reference_t vr_, tree orig_ref_, tree *last_vuse_ptr_,
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vn_lookup_kind vn_walk_kind_, bool tbaa_p_, tree mask_)
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vn_lookup_kind vn_walk_kind_, bool tbaa_p_, tree mask_,
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bool redundant_store_removal_p_)
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: vr (vr_), last_vuse_ptr (last_vuse_ptr_), last_vuse (NULL_TREE),
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mask (mask_), masked_result (NULL_TREE), vn_walk_kind (vn_walk_kind_),
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tbaa_p (tbaa_p_), saved_operands (vNULL), first_set (-2),
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first_base_set (-2), known_ranges (NULL)
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tbaa_p (tbaa_p_), redundant_store_removal_p (redundant_store_removal_p_),
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saved_operands (vNULL), first_set (-2), first_base_set (-2),
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known_ranges (NULL)
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{
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if (!last_vuse_ptr)
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last_vuse_ptr = &last_vuse;
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@ -1862,6 +1864,7 @@ struct vn_walk_cb_data
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tree masked_result;
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vn_lookup_kind vn_walk_kind;
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bool tbaa_p;
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bool redundant_store_removal_p;
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vec<vn_reference_op_s> saved_operands;
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/* The VDEFs of partial defs we come along. */
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@ -2620,6 +2623,19 @@ vn_reference_lookup_3 (ao_ref *ref, tree vuse, void *data_,
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return NULL;
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}
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/* When the def is a CLOBBER we can optimistically disambiguate
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against it since any overlap it would be undefined behavior.
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Avoid this for obvious must aliases to save compile-time though.
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We also may not do this when the query is used for redundant
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store removal. */
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if (!data->redundant_store_removal_p
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&& gimple_clobber_p (def_stmt)
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&& !operand_equal_p (ao_ref_base (&lhs_ref), base, OEP_ADDRESS_OF))
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{
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*disambiguate_only = TR_DISAMBIGUATE;
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return NULL;
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}
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/* Besides valueizing the LHS we can also use access-path based
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disambiguation on the original non-valueized ref. */
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if (!ref->ref
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@ -3604,7 +3620,8 @@ vn_reference_lookup_pieces (tree vuse, alias_set_type set,
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{
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ao_ref r;
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unsigned limit = param_sccvn_max_alias_queries_per_access;
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vn_walk_cb_data data (&vr1, NULL_TREE, NULL, kind, true, NULL_TREE);
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vn_walk_cb_data data (&vr1, NULL_TREE, NULL, kind, true, NULL_TREE,
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false);
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vec<vn_reference_op_s> ops_for_ref;
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if (!valueized_p)
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ops_for_ref = vr1.operands;
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@ -3649,12 +3666,14 @@ vn_reference_lookup_pieces (tree vuse, alias_set_type set,
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MASK is either NULL_TREE, or can be an INTEGER_CST if the result of the
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load is bitwise anded with MASK and so we are only interested in a subset
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of the bits and can ignore if the other bits are uninitialized or
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not initialized with constants. */
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not initialized with constants. When doing redundant store removal
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the caller has to set REDUNDANT_STORE_REMOVAL_P. */
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tree
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vn_reference_lookup (tree op, tree vuse, vn_lookup_kind kind,
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vn_reference_t *vnresult, bool tbaa_p,
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tree *last_vuse_ptr, tree mask)
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tree *last_vuse_ptr, tree mask,
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bool redundant_store_removal_p)
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{
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vec<vn_reference_op_s> operands;
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struct vn_reference_s vr1;
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@ -3732,7 +3751,8 @@ vn_reference_lookup (tree op, tree vuse, vn_lookup_kind kind,
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vr1.type, ops_for_ref))
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ao_ref_init (&r, op);
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vn_walk_cb_data data (&vr1, r.ref ? NULL_TREE : op,
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last_vuse_ptr, kind, tbaa_p, mask);
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last_vuse_ptr, kind, tbaa_p, mask,
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redundant_store_removal_p);
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wvnresult
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= ((vn_reference_t)
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@ -6592,7 +6612,8 @@ eliminate_dom_walker::eliminate_stmt (basic_block b, gimple_stmt_iterator *gsi)
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tree val = NULL_TREE;
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if (lookup_lhs)
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val = vn_reference_lookup (lookup_lhs, gimple_vuse (stmt),
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VN_WALKREWRITE, &vnresult, false);
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VN_WALKREWRITE, &vnresult, false,
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NULL, NULL_TREE, true);
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if (TREE_CODE (rhs) == SSA_NAME)
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rhs = VN_INFO (rhs)->valnum;
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if (val
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@ -265,7 +265,7 @@ tree vn_reference_lookup_pieces (tree, alias_set_type, alias_set_type, tree,
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vec<vn_reference_op_s> ,
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vn_reference_t *, vn_lookup_kind);
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tree vn_reference_lookup (tree, tree, vn_lookup_kind, vn_reference_t *, bool,
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tree * = NULL, tree = NULL_TREE);
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tree * = NULL, tree = NULL_TREE, bool = false);
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void vn_reference_lookup_call (gcall *, vn_reference_t *, vn_reference_t);
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vn_reference_t vn_reference_insert_pieces (tree, alias_set_type, alias_set_type,
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tree, vec<vn_reference_op_s>,
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