Hi,
this is a variant of testcase I have comitted. Once Martin implements SRA
part, we could add next variant that drops -fno-tree-sra.
It seems odd that constant propagation only happens in fre3.
I woud expect fre1 to discover this already.
The IL before fre1 and 3 differs only by:
test ()
{
struct foo foo;
struct bar * barptr.0_1;
struct foo * fooptr.1_2;
- struct bar * barptr.2_3;
- int _8;
+ int _7;
- <bb 2> :
+ <bb 2> [local count: 1073741824]:
foo.val = 0;
barptr.0_1 = barptr;
barptr.0_1->val2 = 123;
fooptr.1_2 = fooptr;
*fooptr.1_2 = foo;
- barptr.2_3 = barptr;
- _8 = barptr.2_3->val2;
+ _7 = barptr.0_1->val2;
foo ={v} {CLOBBER};
- return _8;
+ return _7;
}
Why VN is not able to optimize the barptr access and lookup through
it at once? It looks that could potentially save some need to re-run
GVN since it is common to store pointers to memory and use them multiple
times to access other pointers.
* tree-ssa/alias-access-spath-1.c: new testcase.
Index: gcc.dg/tree-ssa/alias-access-path-1.c
===================================================================
--- gcc.dg/tree-ssa/alias-access-path-1.c (nonexistent)
+++ gcc.dg/tree-ssa/alias-access-path-1.c (working copy)
@@ -0,0 +1,21 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-fre3 -fno-tree-sra" } */
+struct foo
+{
+ int val;
+} *fooptr;
+struct bar
+{
+ struct foo foo;
+ int val2;
+} *barptr;
+int
+test ()
+{
+ struct foo foo = { 0 };
+ barptr->val2 = 123;
+ *fooptr = foo;
+ return barptr->val2;
+}
+
+/* { dg-final { scan-tree-dump-times "return 123" 1 "fre3"} } */
