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| author | Richard Biener <rguenther@suse.de> | 2022-05-09 11:33:44 +0200 |
|---|---|---|
| committer | Richard Biener <rguenther@suse.de> | 2022-05-09 13:42:36 +0200 |
| commit | faabc751d0bb7e7fe86abfe8991b0307d585874a (patch) | |
| tree | cc97e4343aa2d8b777866139a6854a2f0ab9d306 | |
| parent | 93416de0cb72358b95a96fa4341b7b93a6805842 (diff) | |
| download | gcc-faabc751d0bb7e7fe86abfe8991b0307d585874a.zip gcc-faabc751d0bb7e7fe86abfe8991b0307d585874a.tar.gz gcc-faabc751d0bb7e7fe86abfe8991b0307d585874a.tar.bz2 | |
tree-optimization/105517 - avoid offset truncation during VN
When value-numbering an address expression like
&p_74(D)->a1x[4294967295].a1; we are accumulating the byte offset
in an 64bit integer. When later exploiting the duality between
that and a POINTER_PLUS_EXPR we should avoid truncating that
offset to fit in the target specific sizetype. While such
overflows are generally undefined behavior, exploiting this
may leads to spurious missing diagnostics.
2022-05-09 Richard Biener <rguenther@suse.de>
PR tree-optimization/105517
* tree-ssa-sccvn.cc (vn_reference_lookup): Make sure the accumulated
offset can be represented in the POINTER_PLUS_EXPR IL.
(vn_reference_insert): Likewise.
* poly-int.h (sext_hwi): Add poly version of sext_hwi.
| -rw-r--r-- | gcc/poly-int.h | 13 | ||||
| -rw-r--r-- | gcc/tree-ssa-sccvn.cc | 14 |
2 files changed, 25 insertions, 2 deletions
diff --git a/gcc/poly-int.h b/gcc/poly-int.h index 2bf9d98..d085544 100644 --- a/gcc/poly-int.h +++ b/gcc/poly-int.h @@ -1178,6 +1178,19 @@ lshift (const poly_int_pod<N, Ca> &a, const Cb &b) } } +/* Poly version of sext_hwi, with the same interface. */ + +template<unsigned int N, typename C> +inline poly_int<N, HOST_WIDE_INT> +sext_hwi (const poly_int<N, C> &a, unsigned int precision) +{ + poly_int_pod<N, HOST_WIDE_INT> r; + for (unsigned int i = 0; i < N; i++) + r.coeffs[i] = sext_hwi (a.coeffs[i], precision); + return r; +} + + /* Return true if a0 + a1 * x might equal b0 + b1 * x for some nonnegative integer x. */ diff --git a/gcc/tree-ssa-sccvn.cc b/gcc/tree-ssa-sccvn.cc index 7658763..3732d06 100644 --- a/gcc/tree-ssa-sccvn.cc +++ b/gcc/tree-ssa-sccvn.cc @@ -3684,7 +3684,12 @@ vn_reference_lookup (tree op, tree vuse, vn_lookup_kind kind, break; off += vro->off; } - if (i == operands.length () - 1) + if (i == operands.length () - 1 + /* Make sure we the offset we accumulated in a 64bit int + fits the address computation carried out in target + offset precision. */ + && (off.coeffs[0] + == sext_hwi (off.coeffs[0], TYPE_PRECISION (sizetype)))) { gcc_assert (operands[i-1].opcode == MEM_REF); tree ops[2]; @@ -3808,7 +3813,12 @@ vn_reference_insert (tree op, tree result, tree vuse, tree vdef) break; off += vro->off; } - if (i == operands.length () - 1) + if (i == operands.length () - 1 + /* Make sure we the offset we accumulated in a 64bit int + fits the address computation carried out in target + offset precision. */ + && (off.coeffs[0] + == sext_hwi (off.coeffs[0], TYPE_PRECISION (sizetype)))) { gcc_assert (operands[i-1].opcode == MEM_REF); tree ops[2]; |