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| author | Jakub Jelinek <jakub@redhat.com> | 2021-02-25 10:16:55 +0100 |
|---|---|---|
| committer | Jakub Jelinek <jakub@redhat.com> | 2021-02-25 10:16:55 +0100 |
| commit | 3cf52b87ff6938e30883b8f8f542a638635d507d (patch) | |
| tree | ff9120fdd9a7cb6eb72e94e883ec5e08d491d687 /gcc/tree-vrp.c | |
| parent | 5e7c0927cbd115d488d527c86dfc671b22c378db (diff) | |
| download | gcc-3cf52b87ff6938e30883b8f8f542a638635d507d.zip gcc-3cf52b87ff6938e30883b8f8f542a638635d507d.tar.gz gcc-3cf52b87ff6938e30883b8f8f542a638635d507d.tar.bz2 | |
vrp: Handle VCE in vrp_simplify_cond_using_ranges [PR80635]
> So I wonder what other optimizations are prevented here?
> Why does uninit warn with VCE but not with NOP_EXPR? Or does the
> warning disappear because of those other optimizations you mention?
The optimization that it prevents is in this particular case in tree-vrp.c
(vrp_simplify_cond_using_ranges):
if (!is_gimple_assign (def_stmt)
|| !CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (def_stmt)))
return;
so it punts on VIEW_CONVERT_EXPR, with NOP_EXPR it optimizes that:
_9 = (bool) maybe_a$4_7;
if (_9 != 0)
into:
_9 = (bool) maybe_a$4_7;
if (maybe_a$4_7 != 0)
Now, if I apply my patch but manually disable this
vrp_simplify_cond_using_ranges optimization, then the uninit warning is
back, so on the uninit side it is not about VIEW_CONVERT_EXPR vs. NOP_EXPR,
both are bad there, uninit wants the guarding condition to be
that SSA_NAME and not some demotion cast thereof.
We have:
# maybe_a$m_6 = PHI <_5(4), maybe_a$m_4(D)(6)>
# maybe_a$4_7 = PHI <1(4), 0(6)>
...
One of:
_9 = VIEW_CONVERT_EXPR<bool>(maybe_a$4_7);
if (_9 != 0)
or:
_9 = (bool) maybe_a$4_7;
if (_9 != 0)
or:
if (maybe_a$4_7 != 0)
followed by:
goto <bb 11>; [0.00%]
else
goto <bb 14>; [0.00%]
...
<bb 11> [count: 0]:
set (maybe_a$m_6);
and uninit wants to see that maybe_a$m_4(D) is not used if
bb 11 is encountered.
This patch fixes it by teaching vrp_simplify_cond_using_ranges
to handle VCE (when from an integral type) in addition to
NOP_EXPR/CONVERT_EXPR, of course as long as the VCE or demotion
doesn't change any values, i.e. when the range of the VCE or
conversion operand fits into the target type.
2021-02-25 Jakub Jelinek <jakub@redhat.com>
PR tree-optimization/80635
* tree-vrp.c (vrp_simplify_cond_using_ranges): Also handle
VIEW_CONVERT_EXPR if modes are the same, innerop is integral and
has mode precision.
* g++.dg/warn/pr80635-1.C: New test.
* g++.dg/warn/pr80635-2.C: New test.
Diffstat (limited to 'gcc/tree-vrp.c')
| -rw-r--r-- | gcc/tree-vrp.c | 17 |
1 files changed, 14 insertions, 3 deletions
diff --git a/gcc/tree-vrp.c b/gcc/tree-vrp.c index 53eaf9c..8d638ae 100644 --- a/gcc/tree-vrp.c +++ b/gcc/tree-vrp.c @@ -4390,11 +4390,22 @@ vrp_simplify_cond_using_ranges (vr_values *query, gcond *stmt) gimple *def_stmt = SSA_NAME_DEF_STMT (op0); tree innerop; - if (!is_gimple_assign (def_stmt) - || !CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (def_stmt))) + if (!is_gimple_assign (def_stmt)) return; - innerop = gimple_assign_rhs1 (def_stmt); + switch (gimple_assign_rhs_code (def_stmt)) + { + CASE_CONVERT: + innerop = gimple_assign_rhs1 (def_stmt); + break; + case VIEW_CONVERT_EXPR: + innerop = TREE_OPERAND (gimple_assign_rhs1 (def_stmt), 0); + if (!INTEGRAL_TYPE_P (TREE_TYPE (innerop))) + return; + break; + default: + return; + } if (TREE_CODE (innerop) == SSA_NAME && !POINTER_TYPE_P (TREE_TYPE (innerop)) |