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| author | David Malcolm <dmalcolm@redhat.com> | 2020-01-15 15:55:11 -0500 |
|---|---|---|
| committer | David Malcolm <dmalcolm@redhat.com> | 2020-01-17 08:26:14 -0500 |
| commit | 5f0303833d542b273da33e4b149974e739d350e5 (patch) | |
| tree | 654638109512ff4a9b180ab18d7bc6f786dc96cc /gcc | |
| parent | e5e07b68187b9aa334519746c45b8cffc5eb7e5c (diff) | |
| download | gcc-5f0303833d542b273da33e4b149974e739d350e5.zip gcc-5f0303833d542b273da33e4b149974e739d350e5.tar.gz gcc-5f0303833d542b273da33e4b149974e739d350e5.tar.bz2 | |
analyzer: fix handling of negative byte offsets (v2) (PR 93281)
Various 32-bit targets show failures in gcc.dg/analyzer/data-model-1.c
with tests of the form:
__analyzer_eval (q[-2].x == 107024); /* { dg-warning "TRUE" } */
__analyzer_eval (q[-2].y == 107025); /* { dg-warning "TRUE" } */
where they emit UNKNOWN instead.
The root cause is that gimple has a byte-based twos-complement offset
of -16 expressed like this:
_55 = q_92 + 4294967280; (32-bit)
or:
_55 = q_92 + 18446744073709551600; (64-bit)
Within region_model::convert_byte_offset_to_array_index that unsigned
offset was being divided by the element size to get an offset within
an array.
This happened to work on 64-bit target and host, but not elsewhere;
the offset needs to be converted to a signed type before the division
is meaningful.
This patch does so, fixing the failures.
gcc/analyzer/ChangeLog:
PR analyzer/93281
* region-model.cc
(region_model::convert_byte_offset_to_array_index): Convert to
ssizetype before dividing by byte_size. Use fold_binary rather
than fold_build2 to avoid needlessly constructing a tree for the
non-const case.
Diffstat (limited to 'gcc')
| -rw-r--r-- | gcc/analyzer/ChangeLog | 9 | ||||
| -rw-r--r-- | gcc/analyzer/region-model.cc | 10 |
2 files changed, 15 insertions, 4 deletions
diff --git a/gcc/analyzer/ChangeLog b/gcc/analyzer/ChangeLog index 2ca7144..e809018 100644 --- a/gcc/analyzer/ChangeLog +++ b/gcc/analyzer/ChangeLog @@ -1,3 +1,12 @@ +2020-01-17 David Malcolm <dmalcolm@redhat.com> + + PR analyzer/93281 + * region-model.cc + (region_model::convert_byte_offset_to_array_index): Convert to + ssizetype before dividing by byte_size. Use fold_binary rather + than fold_build2 to avoid needlessly constructing a tree for the + non-const case. + 2020-01-15 David Malcolm <dmalcolm@redhat.com> * engine.cc (class impl_region_model_context): Fix comment. diff --git a/gcc/analyzer/region-model.cc b/gcc/analyzer/region-model.cc index 5c39be4..f67572e 100644 --- a/gcc/analyzer/region-model.cc +++ b/gcc/analyzer/region-model.cc @@ -6414,11 +6414,13 @@ region_model::convert_byte_offset_to_array_index (tree ptr_type, /* This might not be a constant. */ tree byte_size = size_in_bytes (elem_type); + /* Try to get a constant by dividing, ensuring that we're in a + signed representation first. */ tree index - = fold_build2 (TRUNC_DIV_EXPR, integer_type_node, - offset_cst, byte_size); - - if (CONSTANT_CLASS_P (index)) + = fold_binary (TRUNC_DIV_EXPR, ssizetype, + fold_convert (ssizetype, offset_cst), + fold_convert (ssizetype, byte_size)); + if (index && TREE_CODE (index) == INTEGER_CST) return get_or_create_constant_svalue (index); } |