Hello,
in my recent phiopt patch enhancing value_replacement to optimize
x!=0?x+y:y, I forgot to check that there is no other PHI (not sure how I
managed to miss that since I copy-pasted the line just below the test).
If there are other phi nodes (with different arguments for those 2
branches), it would be possible to replace the phi argument and stop there
(as value_replacement does for its other transformation). However, I am
chosing to punt. The cost analysis would be different, and I wrote the
transformation assuming that this single-phi test was already done higher
in the function.
Bootstrap+testsuite on x86_64-linux-gnu.
2014-05-12 Marc Glisse <marc.gli...@inria.fr>
PR tree-optimization/61140
gcc/
* tree-ssa-phiopt.c (value_replacement): Punt on multiple phis.
gcc/testsuite/
* gcc.dg/tree-ssa/pr61140.c: New file.
--
Marc GlisseIndex: gcc/testsuite/gcc.dg/tree-ssa/pr61140.c
===================================================================
--- gcc/testsuite/gcc.dg/tree-ssa/pr61140.c (revision 0)
+++ gcc/testsuite/gcc.dg/tree-ssa/pr61140.c (working copy)
@@ -0,0 +1,18 @@
+/* { dg-do run } */
+/* { dg-options "-O2" } */
+
+int a[1] = { 1 }, b = 1, c;
+
+int
+main ()
+{
+ for (; c < 1; c++)
+ if (a[0])
+ {
+ a[0] &= 1;
+ b = 0;
+ }
+ if (b)
+ __builtin_abort ();
+ return 0;
+}
Index: gcc/tree-ssa-phiopt.c
===================================================================
--- gcc/tree-ssa-phiopt.c (revision 210301)
+++ gcc/tree-ssa-phiopt.c (working copy)
@@ -842,20 +842,24 @@ value_replacement (basic_block cond_bb,
/* Now optimize (x != 0) ? x + y : y to just y.
The following condition is too restrictive, there can easily be another
stmt in middle_bb, for instance a CONVERT_EXPR for the second argument.
*/
gimple assign = last_and_only_stmt (middle_bb);
if (!assign || gimple_code (assign) != GIMPLE_ASSIGN
|| gimple_assign_rhs_class (assign) != GIMPLE_BINARY_RHS
|| (!INTEGRAL_TYPE_P (TREE_TYPE (arg0))
&& !POINTER_TYPE_P (TREE_TYPE (arg0))))
return 0;
+ /* Only transform if it removes the condition. */
+ if (!single_non_singleton_phi_for_edges (phi_nodes (gimple_bb (phi)), e0,
e1))
+ return 0;
+
/* Size-wise, this is always profitable. */
if (optimize_bb_for_speed_p (cond_bb)
/* The special case is useless if it has a low probability. */
&& profile_status_for_fn (cfun) != PROFILE_ABSENT
&& EDGE_PRED (middle_bb, 0)->probability < PROB_EVEN
/* If assign is cheap, there is no point avoiding it. */
&& estimate_num_insns (assign, &eni_time_weights)
>= 3 * estimate_num_insns (cond, &eni_time_weights))
return 0;
