Hi,
As reported in PR66768, IVOPTs drops address-space information. Root cause is
IVOPTs fails to preserve base-object during identifying/rewriting address type
iv_use for pointers converted from constant values. This patch just skips
address type iv_use if base-object can't be determined. In the future, better
handling of base-object is needed to fix the issue. Benchmark data show the
added condition is only triggered twice in spec2k6, and the two cases are
actually null-pointer references. I believe that code is dead in benchmark and
is never executed.
Bootstrap and test on x86_64. Is it OK?
2017-02-27 Bin Cheng <bin.ch...@arm.com>
PR tree-optimization/66768
* tree-ssa-loop-ivopts.c (find_interesting_uses_address): Skip addr
iv_use if base object can't be determined.
2017-02-27 Bin Cheng <bin.ch...@arm.com>
PR tree-optimization/66768
* gcc.target/i386/pr66768.c: New test.diff --git a/gcc/testsuite/gcc.target/i386/pr66768.c
b/gcc/testsuite/gcc.target/i386/pr66768.c
new file mode 100644
index 0000000..9a8ad1f
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr66768.c
@@ -0,0 +1,17 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+typedef __seg_gs struct foo_s {
+ int a[20];
+} foo_t;
+
+int sum(void)
+{
+ const foo_t *p = (const foo_t *)0x1234;
+ int i, total=0;
+ for (i=0; i<20; i++)
+ total += p->a[i];
+ return total;
+}
+
+/* { dg-final { scan-assembler "add*.\[ \t\]%gs:" } } */
diff --git a/gcc/tree-ssa-loop-ivopts.c b/gcc/tree-ssa-loop-ivopts.c
index c9d16b2..f3ad373 100644
--- a/gcc/tree-ssa-loop-ivopts.c
+++ b/gcc/tree-ssa-loop-ivopts.c
@@ -2324,6 +2324,10 @@ find_interesting_uses_address (struct ivopts_data *data,
gimple *stmt,
}
civ = alloc_iv (data, base, step);
+ /* Fail if base object of this memory reference is unknown. */
+ if (civ->base_object == NULL_TREE)
+ goto fail;
+
record_group_use (data, op_p, civ, stmt, USE_ADDRESS);
return;
