The following prevents expand_cond_expr_using_cmove from going berzerk
with a large TER tree containing several cond-exprs that eventually
end up failing expansion as cmove. The attempt to re-do TER failed
somehow earlier this year so the following is a simple stop-gap solution.
Bootstrap & regtest ongoing on x86_64-unknown-linux-gnu.
Richard.
2016-12-14 Richard Biener <rguent...@suse.de>
PR middle-end/71632
* expr.c (expand_cond_expr_using_cmove): Bail out early if
we end up recursing via TER.
* gcc.dg/pr71632.c: New testcase.
Index: gcc/expr.c
===================================================================
--- gcc/expr.c (revision 243632)
+++ gcc/expr.c (working copy)
@@ -8096,6 +8098,15 @@ expand_cond_expr_using_cmove (tree treeo
int unsignedp = TYPE_UNSIGNED (type);
machine_mode mode = TYPE_MODE (type);
machine_mode orig_mode = mode;
+ static bool expanding_cond_expr_using_cmove = false;
+
+ /* Conditional move expansion can end up TERing two operands which,
+ when recursively hitting conditional expressions can result in
+ exponential behavior if the cmove expansion ultimatively fails.
+ It's hardly profitable to TER a cmove into a cmove so avoid doing
+ that by failing early if we end up recursing. */
+ if (expanding_cond_expr_using_cmove)
+ return NULL_RTX;
/* If we cannot do a conditional move on the mode, try doing it
with the promoted mode. */
@@ -8109,6 +8120,7 @@ expand_cond_expr_using_cmove (tree treeo
else
temp = assign_temp (type, 0, 1);
+ expanding_cond_expr_using_cmove = true;
start_sequence ();
expand_operands (treeop1, treeop2,
temp, &op1, &op2, EXPAND_NORMAL);
@@ -8143,6 +8155,7 @@ expand_cond_expr_using_cmove (tree treeo
if (comparison_mode == VOIDmode)
comparison_mode = TYPE_MODE (TREE_TYPE (treeop0));
}
+ expanding_cond_expr_using_cmove = false;
if (GET_MODE (op1) != mode)
op1 = gen_lowpart (mode, op1);
Index: gcc/testsuite/gcc.dg/pr71632.c
===================================================================
--- gcc/testsuite/gcc.dg/pr71632.c (revision 0)
+++ gcc/testsuite/gcc.dg/pr71632.c (working copy)
@@ -0,0 +1,53 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -ftree-loop-if-convert" } */
+
+void
+foo (double d, double *p, double *q)
+{
+ int i;
+ for (i = 0; i < 64; i++)
+ {
+ double t1 = d > p[0] ? 1.0 : 0.0;
+ double t2 = t1 > p[1] ? 1.0 : 0.0;
+ double t3 = t2 > p[2] ? 1.0 : 0.0;
+ double t4 = t3 > p[3] ? 1.0 : 0.0;
+ double t5 = t4 > p[4] ? 1.0 : 0.0;
+ double t6 = t5 > p[5] ? 1.0 : 0.0;
+ double t7 = t6 > p[6] ? 1.0 : 0.0;
+ double t8 = t7 > p[7] ? 1.0 : 0.0;
+ double t9 = t8 > p[8] ? 1.0 : 0.0;
+ double t10 = t9 > p[9] ? 1.0 : 0.0;
+ double t11 = t10 > p[10] ? 1.0 : 0.0;
+ double t12 = t11 > p[11] ? 1.0 : 0.0;
+ double t13 = t12 > p[12] ? 1.0 : 0.0;
+ double t14 = t13 > p[13] ? 1.0 : 0.0;
+ double t15 = t14 > p[14] ? 1.0 : 0.0;
+ double t16 = t15 > p[15] ? 1.0 : 0.0;
+ double t17 = t16 > p[16] ? 1.0 : 0.0;
+ double t18 = t17 > p[17] ? 1.0 : 0.0;
+ double t19 = t18 > p[18] ? 1.0 : 0.0;
+ double t20 = t19 > p[19] ? 1.0 : 0.0;
+ double t21 = t20 > p[20] ? 1.0 : 0.0;
+ double t22 = t21 > p[21] ? 1.0 : 0.0;
+ double t23 = t22 > p[22] ? 1.0 : 0.0;
+ double t24 = t23 > p[23] ? 1.0 : 0.0;
+ double t25 = t24 > p[24] ? 1.0 : 0.0;
+ double t26 = t25 > p[25] ? 1.0 : 0.0;
+ double t27 = t26 > p[26] ? 1.0 : 0.0;
+ double t28 = t27 > p[27] ? 1.0 : 0.0;
+ double t29 = t28 > p[28] ? 1.0 : 0.0;
+ double t30 = t29 > p[29] ? 1.0 : 0.0;
+ double t31 = t30 > p[30] ? 1.0 : 0.0;
+ double t32 = t31 > p[31] ? 1.0 : 0.0;
+ double t33 = t32 > p[32] ? 1.0 : 0.0;
+ double t34 = t33 > p[33] ? 1.0 : 0.0;
+ double t35 = t34 > p[34] ? 1.0 : 0.0;
+ double t36 = t35 > p[35] ? 1.0 : 0.0;
+ double t37 = t36 > p[36] ? 1.0 : 0.0;
+ double t38 = t37 > p[37] ? 1.0 : 0.0;
+ double t39 = t38 > p[38] ? 1.0 : 0.0;
+ *q = t39;
+ p += 39;
+ q++;
+ }
+}
