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re PR middle-end/83215 (C++: struct with char-array assumed to alias with everything)

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2018-11-20  Richard Biener  <rguenther@suse.de>

	PR middle-end/83215
	* alias.c (component_uses_parent_alias_set_from): Remove
	alias-set zero and TYPE_TYPELESS_STORAGE case both already
	handled in other ways.

	* g++.dg/tree-ssa/pr83215.C: New testcase.

From-SVN: r266305
This commit is contained in:
Richard Biener 2018-11-20 09:31:06 +00:00 committed by Richard Biener
parent 643427d70f
commit dc3221e1e3
4 changed files with 32 additions and 9 deletions
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7
gcc/ChangeLog
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@ -1,3 +1,10 @@
2018-11-20 Richard Biener <rguenther@suse.de>
PR middle-end/83215
* alias.c (component_uses_parent_alias_set_from): Remove
alias-set zero and TYPE_TYPELESS_STORAGE case both already
handled in other ways.
2018-11-20 Richard Biener <rguenther@suse.de>
PR tree-optimization/88087

10
gcc/alias.c
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@ -601,8 +601,7 @@ objects_must_conflict_p (tree t1, tree t2)
/* Return the outermost parent of component present in the chain of
component references handled by get_inner_reference in T with the
following property:
- the component is non-addressable, or
- the parent has alias set zero,
- the component is non-addressable
or NULL_TREE if no such parent exists. In the former cases, the alias
set of this parent is the alias set that must be used for T itself. */
@ -611,10 +610,6 @@ component_uses_parent_alias_set_from (const_tree t)
{
const_tree found = NULL_TREE;
if (AGGREGATE_TYPE_P (TREE_TYPE (t))
&& TYPE_TYPELESS_STORAGE (TREE_TYPE (t)))
return const_cast <tree> (t);
while (handled_component_p (t))
{
switch (TREE_CODE (t))
@ -652,9 +647,6 @@ component_uses_parent_alias_set_from (const_tree t)
gcc_unreachable ();
}
if (get_alias_set (TREE_TYPE (TREE_OPERAND (t, 0))) == 0)
found = t;
t = TREE_OPERAND (t, 0);
}

5
gcc/testsuite/ChangeLog
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@ -1,3 +1,8 @@
2018-11-20 Richard Biener <rguenther@suse.de>
PR middle-end/83215
* g++.dg/tree-ssa/pr83215.C: New testcase.
2018-11-20 Eric Botcazou <ebotcazou@adacore.com>
* gcc.c-torture/execute/20181120-1.c: New test.

19
gcc/testsuite/g++.dg/tree-ssa/pr83215.C Normal file
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@ -0,0 +1,19 @@
// { dg-do compile }
// { dg-options "-O2 -fdump-tree-fre1" }
struct mytest
{
float a;
char buf[256];
};
int foo(mytest *m, int *i)
{
int tmp = *i;
m->a = 10.0f;
return tmp + *i;
}
// we should be able to CSE *i despite mytest having a cbar[] buffer
// and thus being subject to TYPE_TYPELESS_STORAGE
// { dg-final { scan-tree-dump-times "\\*i" 1 "fre1" } }