Hi,
This patch partially reverts part of r235513 to fix PR71347, the original patch
is to improve compilation time for a small amount. Root cause as analyzed in
bugzilla PR is that we can't skip computing cost for sub iv_use if it has
different position to the first use in group. The patch also includes a new
test.
Bootstrap and test on x86_64. Is it OK?
Thanks,
bin
2016-05-31 Bin Cheng <bin.ch...@arm.com>
PR tree-optimization/71347
* tree-ssa-loop-ivopts.c (determine_group_iv_cost_address): Compute
cost for all uses in group.
gcc/testsuite/ChangeLog
2016-05-31 Bin Cheng <bin.ch...@arm.com>
PR tree-optimization/71347
* gcc.dg/tree-ssa/pr71347.c: New test.
diff --git a/gcc/tree-ssa-loop-ivopts.c b/gcc/tree-ssa-loop-ivopts.c
index 1e8d637..25b9780 100644
--- a/gcc/tree-ssa-loop-ivopts.c
+++ b/gcc/tree-ssa-loop-ivopts.c
@@ -5115,7 +5115,7 @@ determine_group_iv_cost_address (struct ivopts_data *data,
{
unsigned i;
bitmap depends_on;
- bool can_autoinc, first = true;
+ bool can_autoinc;
iv_inv_expr_ent *inv_expr = NULL;
struct iv_use *use = group->vuses[0];
comp_cost sum_cost = no_cost, cost;
@@ -5142,30 +5142,11 @@ determine_group_iv_cost_address (struct ivopts_data
*data,
{
struct iv_use *next = group->vuses[i];
- /* Compute cost for the first use with different offset to the main
- use and add it afterwards. Costs for these uses could be quite
- different. Given below uses in a group:
- use 0 : {base + A + offset_0, step}
- use 0.1: {base + A + offset_0, step}
- use 0.2: {base + A + offset_1, step}
- use 0.3: {base + A + offset_2, step}
- when we need to compute costs with candidate:
- cand 1 : {base + B + offset_0, step}
-
- The first use with different offset is use 0.2, its cost is larger
- than cost of use 0/0.1 because we need to compute:
- A - B + offset_1 - offset_0
- rather than:
- A - B. */
- if (first && next->addr_offset != use->addr_offset)
- {
- first = false;
- cost = get_computation_cost (data, next, cand, true,
- NULL, &can_autoinc, NULL);
- /* Remove setup cost. */
- if (!cost.infinite_cost_p ())
- cost -= cost.scratch;
- }
+ /* TODO: We could skip computing cost for sub iv_use when it has the
+ same cost as the first iv_use, but the cost really depends on the
+ offset and where the iv_use is. */
+ cost = get_computation_cost (data, next, cand, true,
+ NULL, &can_autoinc, NULL);
sum_cost += cost;
}
set_group_iv_cost (data, group, cand, sum_cost, depends_on,
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr71347.c
b/gcc/testsuite/gcc.dg/tree-ssa/pr71347.c
new file mode 100644
index 0000000..7e5ad49
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr71347.c
@@ -0,0 +1,17 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+double in;
+extern void Write (double);
+void foo (void)
+{
+ static double X[9];
+ int i;
+ X[1] = in * in;
+ for (i = 2; i <= 8; i++)
+ X[i] = X[i - 1] * X[1];
+ Write (X[5]);
+}
+
+/* Load of X[i - i] can be omitted by reusing X[i] in previous iteration. */
+/* { dg-final { scan-tree-dump-not ".* = MEM.*;" "optimized"} } */
