Been sitting in my tree (fixes SPEC 2k6 miscompares).
Bootstrapped and tested on x86-64-unknown-linux-gnu, applied.
Richard.
2017-12-04 Richard Biener <rguent...@suse.de>
PR tree-optimization/83255
* graphite-isl-ast-to-gimple.c (translate_isl_ast_node_for):
Re-add zero-iteration check.
* gcc.dg/graphite/pr83255.c: New testcase.
Index: gcc/graphite-isl-ast-to-gimple.c
===================================================================
--- gcc/graphite-isl-ast-to-gimple.c (revision 255375)
+++ gcc/graphite-isl-ast-to-gimple.c (working copy)
@@ -720,6 +720,32 @@ translate_isl_ast_node_for (loop_p conte
ub = integer_zero_node;
edge last_e = single_succ_edge (split_edge (next_e));
+
+ /* Compensate for the fact that we emit a do { } while loop from
+ a for ISL AST.
+ ??? We often miss constraints on niter because the SESE region
+ doesn't cover loop header copies. Ideally we'd add constraints
+ for all relevant dominating conditions. */
+ if (TREE_CODE (lb) == INTEGER_CST && TREE_CODE (ub) == INTEGER_CST
+ && tree_int_cst_compare (lb, ub) <= 0)
+ ;
+ else
+ {
+ tree one = build_one_cst (POINTER_TYPE_P (type) ? sizetype : type);
+ /* Adding +1 and using LT_EXPR helps with loop latches that have a
+ loop iteration count of "PARAMETER - 1". For PARAMETER == 0 this
+ becomes 2^k-1 due to integer overflow, and the condition lb <= ub
+ is true, even if we do not want this. However lb < ub + 1 is false,
+ as expected. */
+ tree ub_one = fold_build2 (POINTER_TYPE_P (type)
+ ? POINTER_PLUS_EXPR : PLUS_EXPR,
+ type, ub, one);
+ create_empty_if_region_on_edge (next_e,
+ fold_build2 (LT_EXPR, boolean_type_node,
+ lb, ub_one));
+ next_e = get_true_edge_from_guard_bb (next_e->dest);
+ }
+
translate_isl_ast_for_loop (context_loop, node, next_e,
type, lb, ub, ip);
return last_e;
Index: gcc/testsuite/gcc.dg/graphite/pr83255.c
===================================================================
--- gcc/testsuite/gcc.dg/graphite/pr83255.c (nonexistent)
+++ gcc/testsuite/gcc.dg/graphite/pr83255.c (working copy)
@@ -0,0 +1,28 @@
+/* { dg-do run } */
+/* { dg-options "-O -floop-nest-optimize -fdump-tree-graphite-details" } */
+
+int rx, in;
+
+int
+main (void)
+{
+ const int tj = 3;
+ int as[tj];
+ static int l4;
+
+ while (l4 < 1)
+ {
+ for (rx = 0; rx < tj; ++rx)
+ {
+ for (in = 0; in < tj; ++in)
+ as[in] = 1;
+ as[rx] = 0;
+ }
+ ++l4;
+ }
+
+ if (as[tj - 1] != 0)
+ __builtin_abort ();
+}
+
+/* { dg-final { scan-tree-dump "loop nest optimized" "graphite" } } */
