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tree-optimization/102608 - avoid CSEing .DEFERRED_INIT

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This makes VN not CSE .DEFERRED_INIT which confuses uninit
analysis which reports the wrong decl when facing copies
of not initialized data.

2021-10-07  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/102608
	* tree-ssa-sccvn.c (visit_stmt): Drop .DEFERRED_INIT to
	varying.
This commit is contained in:
Richard Biener 2021-10-07 14:24:03 +02:00
parent 4fcf7f6800
commit 1ebf2c14c6
1 changed files with 24 additions and 21 deletions
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45
gcc/tree-ssa-sccvn.c
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@ -5668,27 +5668,30 @@ visit_stmt (gimple *stmt, bool backedges_varying_p = false)
&& TREE_CODE (TREE_OPERAND (fn, 0)) == FUNCTION_DECL)
extra_fnflags = flags_from_decl_or_type (TREE_OPERAND (fn, 0));
}
if (/* Calls to the same function with the same vuse
and the same operands do not necessarily return the same
value, unless they're pure or const. */
((gimple_call_flags (call_stmt) | extra_fnflags)
& (ECF_PURE | ECF_CONST))
/* If calls have a vdef, subsequent calls won't have
the same incoming vuse. So, if 2 calls with vdef have the
same vuse, we know they're not subsequent.
We can value number 2 calls to the same function with the
same vuse and the same operands which are not subsequent
the same, because there is no code in the program that can
compare the 2 values... */
|| (gimple_vdef (call_stmt)
/* ... unless the call returns a pointer which does
not alias with anything else. In which case the
information that the values are distinct are encoded
in the IL. */
&& !(gimple_call_return_flags (call_stmt) & ERF_NOALIAS)
/* Only perform the following when being called from PRE
which embeds tail merging. */
&& default_vn_walk_kind == VN_WALK))
if ((/* Calls to the same function with the same vuse
and the same operands do not necessarily return the same
value, unless they're pure or const. */
((gimple_call_flags (call_stmt) | extra_fnflags)
& (ECF_PURE | ECF_CONST))
/* If calls have a vdef, subsequent calls won't have
the same incoming vuse. So, if 2 calls with vdef have the
same vuse, we know they're not subsequent.
We can value number 2 calls to the same function with the
same vuse and the same operands which are not subsequent
the same, because there is no code in the program that can
compare the 2 values... */
|| (gimple_vdef (call_stmt)
/* ... unless the call returns a pointer which does
not alias with anything else. In which case the
information that the values are distinct are encoded
in the IL. */
&& !(gimple_call_return_flags (call_stmt) & ERF_NOALIAS)
/* Only perform the following when being called from PRE
which embeds tail merging. */
&& default_vn_walk_kind == VN_WALK))
/* Do not process .DEFERRED_INIT since that confuses uninit
analysis. */
&& !gimple_call_internal_p (call_stmt, IFN_DEFERRED_INIT))
changed = visit_reference_op_call (lhs, call_stmt);
else
changed = defs_to_varying (call_stmt);