Fix points_to_local_or_readonly_memory_p wrt TARGET_MEM_REF

TARGET_MEM_REF can be used to offset constant base into a memory object (to
produce lea instruction).  This confuses points_to_local_or_readonly_memory_p
which treats the constant address as a base of the access.

Bootstrapped/regtsted x86_64-linux, comitted.
Honza

gcc/ChangeLog:

	PR ipa/113787
	* ipa-fnsummary.cc (points_to_local_or_readonly_memory_p): Do not
	look into TARGET_MEM_REFS with constant opreand 0.

gcc/testsuite/ChangeLog:

	* gcc.c-torture/execute/pr113787.c: New test.

1 files changed, 38 insertions, 0 deletions

diff --git a/gcc/testsuite/gcc.c-torture/execute/pr113787.c b/gcc/testsuite/gcc.c-torture/execute/pr113787.c
new file mode 100644
index 0000000..702b6c3
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/pr113787.c
@@ -0,0 +1,38 @@
+void foo(int x, int y, int z, int d, int *buf)
+{
+  for(int i = z; i < y-z; ++i)
+    for(int j = 0; j < d; ++j)
+      /* buf[x(i+1) + j] = buf[x(i+1)-j-1] */
+      buf[i*x+(x-z+j)] = buf[i*x+(x-z-1-j)];
+}
+
+void bar(int x, int y, int z, int d, int *buf)
+{
+  for(int i = 0; i < d; ++i)
+    for(int j = z; j < x-z; ++j)
+      /* buf[j+(y+i)*x] = buf[j+(y-1-i)*x] */
+      buf[j+(y-z+i)*x] = buf[j+(y-z-1-i)*x];
+}
+
+__attribute__((noipa))
+void baz(int x, int y, int d, int *buf)
+{
+  foo(x, y, 0, d, buf);
+  bar(x, y, 0, d, buf);
+}
+
+int main(void)
+{
+  int a[] = { 1, 2, 3 };
+  baz (1, 2, 1, a);
+  /* foo does:
+     buf[1] = buf[0];
+     buf[2] = buf[1];
+
+     bar does:
+     buf[2] = buf[1]; (no-op)
+     so we should have { 1, 1, 1 }.  */
+  for (int i = 0; i < 3; i++)
+    if (a[i] != 1)
+      __builtin_abort ();
+}