In this PR we hit the issue that when CCP faces a conditional which
is (still) undefined it will consider all outgoing edges executable.
Eventually we'll reverse that decision (but without reflecting that
in the lattice), but it's too late then if a PHI node merging
the edges has been evaluated to a copy defined in the not executable
path.
Thus the following patch makes sure we never even start with such
a case (SSA propagator iteration order hopefully makes sure
this doesn't pessimize things in non-loop regions - I have a patch
to fix some iteration order oddities of it).
Bootstrap and regtest running on x86_64-unknown-linux-gnu.
Richard.
2015-07-06 Richard Biener <rguent...@suse.de>
PR tree-optimization/66772
* tree-ssa-ccp.c (ccp_visit_phi_node): Make sure that copy
values are available in the PHI node BB when there are
still unexecutable edges.
* gcc.dg/torture/pr66772-1.c: New testcase.
* gcc.dg/torture/pr66772-2.c: Likewise.
Index: gcc/tree-ssa-ccp.c
===================================================================
*** gcc/tree-ssa-ccp.c (revision 225449)
--- gcc/tree-ssa-ccp.c (working copy)
*************** ccp_visit_phi_node (gphi *phi)
*** 1081,1086 ****
--- 1094,1100 ----
new_val.mask = 0;
bool first = true;
+ bool non_exec_edge = false;
for (i = 0; i < gimple_phi_num_args (phi); i++)
{
/* Compute the meet operator over all the PHI arguments flowing
*************** ccp_visit_phi_node (gphi *phi)
*** 1121,1126 ****
--- 1135,1156 ----
if (new_val.lattice_val == VARYING)
break;
}
+ else
+ non_exec_edge = true;
+ }
+
+ /* In case there were non-executable edges and the value is a copy
+ make sure its definition dominates the PHI node. */
+ if (non_exec_edge
+ && new_val.lattice_val == CONSTANT
+ && TREE_CODE (new_val.value) == SSA_NAME
+ && ! SSA_NAME_IS_DEFAULT_DEF (new_val.value)
+ && ! dominated_by_p (CDI_DOMINATORS, gimple_bb (phi),
+ gimple_bb (SSA_NAME_DEF_STMT (new_val.value))))
+ {
+ new_val.lattice_val = VARYING;
+ new_val.value = NULL_TREE;
+ new_val.mask = -1;
}
if (dump_file && (dump_flags & TDF_DETAILS))
Index: gcc/testsuite/gcc.dg/torture/pr66733-1.c
===================================================================
*** gcc/testsuite/gcc.dg/torture/pr66733-1.c (revision 0)
--- gcc/testsuite/gcc.dg/torture/pr66733-1.c (working copy)
***************
*** 0 ****
--- 1,28 ----
+ /* { dg-do compile } */
+
+ int a;
+
+ int
+ fn1 ()
+ {
+ return 1;
+ }
+
+ void
+ fn2 ()
+ {
+ int b, j;
+ for (;;)
+ {
+ int c = 1;
+ if (j)
+ {
+ if (c)
+ break;
+ }
+ else
+ b = a;
+ fn1 () && b;
+ j = fn1 ();
+ }
+ }
Index: gcc/testsuite/gcc.dg/torture/pr66733-2.c
===================================================================
*** gcc/testsuite/gcc.dg/torture/pr66733-2.c (revision 0)
--- gcc/testsuite/gcc.dg/torture/pr66733-2.c (working copy)
***************
*** 0 ****
--- 1,46 ----
+ /* { dg-do compile } */
+
+ int a, b, c, e, f;
+
+ void fn1 (int p) { }
+
+ int
+ fn2 (int p)
+ {
+ return a ? p % a : 0;
+ }
+
+ short
+ fn3 (int p)
+ {
+ return (1 >> p) < 1 ? 1 : p;
+ }
+
+ int
+ fn4 ()
+ {
+ int g = 0, h = 1;
+ if (b)
+ goto lbl;
+ fn2 (0);
+ if (fn3 (1))
+ fn1 (e && c);
+ if (h)
+ {
+ int i = 1;
+ lbl:
+ if (i)
+ return 0;
+ for (; g < 1; g++)
+ ;
+ }
+ for (;;)
+ f || g > 0;
+ }
+
+ int
+ main ()
+ {
+ fn4 ();
+ return 0;
+ }
