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| author | Richard Biener <rguenther@suse.de> | 2019-07-08 11:46:26 +0000 |
|---|---|---|
| committer | Richard Biener <rguenth@gcc.gnu.org> | 2019-07-08 11:46:26 +0000 |
| commit | 08dfb1d682a707f7319aafec28edda424395dae5 (patch) | |
| tree | dd659e7669e81dbe8c6fa879216ee29a505dd80a /gcc/tree-ssa-sccvn.c | |
| parent | b68cae81760cd158ee465466280fc0df58e6a768 (diff) | |
| download | gcc-08dfb1d682a707f7319aafec28edda424395dae5.zip gcc-08dfb1d682a707f7319aafec28edda424395dae5.tar.gz gcc-08dfb1d682a707f7319aafec28edda424395dae5.tar.bz2 | |
re PR tree-optimization/91108 (Fails to pun through unions)
2019-07-08 Richard Biener <rguenther@suse.de>
PR tree-optimization/91108
* tree-ssa-sccvn.c: Include builtins.h.
(vn_reference_lookup_3): Use only alignment constraints to
verify same-valued store disambiguation.
* gcc.dg/tree-ssa/ssa-fre-61.c: Adjust back.
* gcc.dg/tree-ssa/ssa-fre-78.c: New testcase.
From-SVN: r273232
Diffstat (limited to 'gcc/tree-ssa-sccvn.c')
| -rw-r--r-- | gcc/tree-ssa-sccvn.c | 30 |
1 files changed, 12 insertions, 18 deletions
diff --git a/gcc/tree-ssa-sccvn.c b/gcc/tree-ssa-sccvn.c index 3c45adc..854222a 100644 --- a/gcc/tree-ssa-sccvn.c +++ b/gcc/tree-ssa-sccvn.c @@ -70,6 +70,7 @@ along with GCC; see the file COPYING3. If not see #include "tree-ssa-loop.h" #include "tree-scalar-evolution.h" #include "tree-ssa-loop-niter.h" +#include "builtins.h" #include "tree-ssa-sccvn.h" /* This algorithm is based on the SCC algorithm presented by Keith @@ -2248,24 +2249,10 @@ vn_reference_lookup_3 (ao_ref *ref, tree vuse, void *data_, /* If we reach a clobbering statement try to skip it and see if we find a VN result with exactly the same value as the possible clobber. In this case we can ignore the clobber - and return the found value. - Note that we don't need to worry about partial overlapping - accesses as we then can use TBAA to disambiguate against the - clobbering statement when looking up a load (thus the - VN_WALKREWRITE guard). */ - if (data->vn_walk_kind == VN_WALKREWRITE - && is_gimple_reg_type (TREE_TYPE (lhs)) + and return the found value. */ + if (is_gimple_reg_type (TREE_TYPE (lhs)) && types_compatible_p (TREE_TYPE (lhs), vr->type) - /* The overlap restriction breaks down when either access - alias-set is zero. Still for accesses of the size of - an addressable unit there can be no overlaps. Overlaps - between different union members are not an issue since - activation of a union member via a store makes the - values of untouched bytes unspecified. */ - && (known_eq (ref->size, BITS_PER_UNIT) - || (flag_strict_aliasing - && get_alias_set (lhs) != 0 - && ao_ref_alias_set (ref) != 0))) + && ref->ref) { tree *saved_last_vuse_ptr = data->last_vuse_ptr; /* Do not update last_vuse_ptr in vn_reference_lookup_2. */ @@ -2284,7 +2271,14 @@ vn_reference_lookup_3 (ao_ref *ref, tree vuse, void *data_, if (TREE_CODE (rhs) == SSA_NAME) rhs = SSA_VAL (rhs); if (vnresult->result - && operand_equal_p (vnresult->result, rhs, 0)) + && operand_equal_p (vnresult->result, rhs, 0) + /* We have to honor our promise about union type punning + and also support arbitrary overlaps with + -fno-strict-aliasing. So simply resort to alignment to + rule out overlaps. Do this check last because it is + quite expensive compared to the hash-lookup above. */ + && multiple_p (get_object_alignment (ref->ref), ref->size) + && multiple_p (get_object_alignment (lhs), ref->size)) return res; } } |