Not because it might be terribly important but the recent change
triggered a latent(?) issue on AIX which broke bootstrap. Let's
try if another change mitigates that.
The change basically allows devirt-to-const/pure to be taken
into account during the value-numbering rather than only in
followup passes (after we committed the devirtualization).
Bootstrap / regtest running on x86_64-unknown-linux-gnu.
Richard.
2016-09-22 Richard Biener <rguent...@suse.de>
* tree-ssa-sccvn.c (visit_reference_op_call): Value number
virtual definition to virtual use if the call devirtualizes
to a const or pure function.
(visit_use): Also visit calls we can devirtualize to a
const or pure function.
Index: gcc/tree-ssa-sccvn.c
===================================================================
*** gcc/tree-ssa-sccvn.c (revision 240353)
--- gcc/tree-ssa-sccvn.c (working copy)
*************** visit_reference_op_call (tree lhs, gcall
*** 3486,3492 ****
vn_reference_t vr2;
vn_reference_s **slot;
if (vdef)
! changed |= set_ssa_val_to (vdef, vdef);
if (lhs)
changed |= set_ssa_val_to (lhs, lhs);
vr2 = current_info->references_pool->allocate ();
--- 3593,3615 ----
vn_reference_t vr2;
vn_reference_s **slot;
if (vdef)
! {
! /* If we value numbered an indirect functions function to
! one not clobbering memory value number its VDEF to its
! VUSE. */
! tree fn = gimple_call_fn (stmt);
! tree vdef_val = vdef;
! if (fn && TREE_CODE (fn) == SSA_NAME)
! {
! fn = SSA_VAL (fn);
! if (TREE_CODE (fn) == ADDR_EXPR
! && TREE_CODE (TREE_OPERAND (fn, 0)) == FUNCTION_DECL
! && (flags_from_decl_or_type (TREE_OPERAND (fn, 0))
! & (ECF_CONST | ECF_PURE)))
! vdef_val = vuse_ssa_val (gimple_vuse (stmt));
! }
! changed |= set_ssa_val_to (vdef, vdef_val);
! }
if (lhs)
changed |= set_ssa_val_to (lhs, lhs);
vr2 = current_info->references_pool->allocate ();
*************** visit_use (tree use)
*** 3913,3923 ****
}
}
if (!gimple_call_internal_p (call_stmt)
&& (/* 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) & (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.
--- 4035,4056 ----
}
}
+ /* Pick up flags from a devirtualization target. */
+ tree fn = gimple_call_fn (stmt);
+ int extra_fnflags = 0;
+ if (fn && TREE_CODE (fn) == SSA_NAME)
+ {
+ fn = SSA_VAL (fn);
+ if (TREE_CODE (fn) == ADDR_EXPR
+ && TREE_CODE (TREE_OPERAND (fn, 0)) == FUNCTION_DECL)
+ extra_fnflags = flags_from_decl_or_type (TREE_OPERAND (fn, 0));
+ }
if (!gimple_call_internal_p (call_stmt)
&& (/* 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.
Index: gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-56.c
===================================================================
*** gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-56.c (revision 0)
--- gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-56.c (working copy)
***************
*** 0 ****
--- 1,26 ----
+ /* { dg-do compile } */
+ /* { dg-options "-O -fdump-tree-fre1" } */
+
+ int x = 1;
+ int __attribute__((noinline,noclone)) fn ()
+ {
+ return x;
+ }
+ int (*f)();
+ int main ()
+ {
+ int res;
+ f = fn;
+ x = 0;
+ res = f ();
+ res += x;
+ if (res != 0)
+ __builtin_abort ();
+ return 0;
+ }
+
+ /* We should be able to optimize the load from x in main and thus the
+ addition. */
+
+ /* { dg-final { scan-tree-dump-times "= x;" 1 "fre1" } } */
+ /* { dg-final { scan-tree-dump-times " \\\+ " 0 "fre1" } } */
