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Improve return slot handling in ipa-modref

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gcc/ChangeLog:

	* ipa-modref.c (analyze_ssa_name_flags): Improve handling of return slot.

gcc/testsuite/ChangeLog:

	* g++.dg/tree-ssa/modref-1.C: New test.
This commit is contained in:
Jan Hubicka 2021-08-23 09:21:36 +02:00
parent f93f086891
commit 59f38935d1
2 changed files with 42 additions and 13 deletions
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23
gcc/ipa-modref.c
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@ -1709,19 +1709,8 @@ analyze_ssa_name_flags (tree name, vec<modref_lattice> &lattice, int depth,
if (gimple_call_fn (use_stmt) == name)
lattice[index].merge (~EAF_NOCLOBBER);
/* Return slot optimization would require bit of propagation;
give up for now. */
if (gimple_call_return_slot_opt_p (call)
&& gimple_call_lhs (call) != NULL_TREE
&& TREE_ADDRESSABLE (TREE_TYPE (gimple_call_lhs (call))))
{
if (dump_file)
fprintf (dump_file, "%*s Unhandled return slot opt\n",
depth * 4, "");
lattice[index].merge (0);
}
/* Recursion would require bit of propagation; give up for now. */
else if (callee && !ipa && recursive_call_p (current_function_decl,
if (callee && !ipa && recursive_call_p (current_function_decl,
callee))
lattice[index].merge (0);
else
@ -1735,7 +1724,15 @@ analyze_ssa_name_flags (tree name, vec<modref_lattice> &lattice, int depth,
/* Handle *name = func (...). */
if (gimple_call_lhs (call)
&& memory_access_to (gimple_call_lhs (call), name))
lattice[index].merge_direct_store ();
{
lattice[index].merge_direct_store ();
/* Return slot optimization passes address of
LHS to callee via hidden parameter and this
may make LHS to escape. See PR 98499. */
if (gimple_call_return_slot_opt_p (call)
&& TREE_ADDRESSABLE (TREE_TYPE (gimple_call_lhs (call))))
lattice[index].merge (EAF_NOREAD | EAF_DIRECT);
}
/* We do not track accesses to the static chain (we could)
so give up. */

32
gcc/testsuite/g++.dg/tree-ssa/modref-1.C Normal file
View file

@ -0,0 +1,32 @@
/* { dg-do compile } */
/* { dg-options "-O2 -fdump-tree-optimized" } */
struct S { int a; char b[20]; S(); S(S const&); };
volatile int global;
__attribute__ ((noinline,noclone))
struct S noescape (int *b)
{
struct S a;
a.a = b!=0;
global = 1;
return a;
}
void escape (struct S *p);
__attribute__ ((noinline,noclone))
int
test(int *b)
{
struct S s = noescape (b);
escape (&s);
return *b;
}
int test2()
{
int b=1234;
test (&b);
return b;
}
// ipa-modref should analyze parameter B of test as noescape.
// { dg-final { scan-tree-dump "return 1234" } }