This adds back a folding that worked in GCC 4.5 times by amending
the pattern that handles other cases of address vs. SSA name
comparisons.
Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed.
Richard.
2020-02-04 Richard Biener <rguent...@suse.de>
PR tree-optimization/93538
* match.pd (addr EQ/NE ptr): Amend to handle &ptr->x EQ/NE ptr.
* gcc.dg/tree-ssa/forwprop-38.c: New testcase.
---
gcc/match.pd | 33 +++++++++++++++++++----------
gcc/testsuite/gcc.dg/tree-ssa/forwprop-38.c | 13 ++++++++++++
2 files changed, 35 insertions(+), 11 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/forwprop-38.c
diff --git a/gcc/match.pd b/gcc/match.pd
index 780eb6a8959..a9215f971b9 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -4267,19 +4267,30 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
{ constant_boolean_node (above ? false : true, type); }))))))))))))
(for cmp (eq ne)
- /* A local variable can never be pointed to by
- the default SSA name of an incoming parameter.
- SSA names are canonicalized to 2nd place. */
(simplify
+ /* SSA names are canonicalized to 2nd place. */
(cmp addr@0 SSA_NAME@1)
- (if (SSA_NAME_IS_DEFAULT_DEF (@1)
- && TREE_CODE (SSA_NAME_VAR (@1)) == PARM_DECL)
- (with { tree base = get_base_address (TREE_OPERAND (@0, 0)); }
- (if (TREE_CODE (base) == VAR_DECL
- && auto_var_in_fn_p (base, current_function_decl))
- (if (cmp == NE_EXPR)
- { constant_boolean_node (true, type); }
- { constant_boolean_node (false, type); }))))))
+ (with
+ { poly_int64 off; tree base; }
+ /* A local variable can never be pointed to by
+ the default SSA name of an incoming parameter. */
+ (if (SSA_NAME_IS_DEFAULT_DEF (@1)
+ && TREE_CODE (SSA_NAME_VAR (@1)) == PARM_DECL
+ && (base = get_base_address (TREE_OPERAND (@0, 0)))
+ && TREE_CODE (base) == VAR_DECL
+ && auto_var_in_fn_p (base, current_function_decl))
+ (if (cmp == NE_EXPR)
+ { constant_boolean_node (true, type); }
+ { constant_boolean_node (false, type); })
+ /* If the address is based on @1 decide using the offset. */
+ (if ((base = get_addr_base_and_unit_offset (TREE_OPERAND (@0, 0), &off))
+ && TREE_CODE (base) == MEM_REF
+ && TREE_OPERAND (base, 0) == @1)
+ (with { off += mem_ref_offset (base).force_shwi (); }
+ (if (known_ne (off, 0))
+ { constant_boolean_node (cmp == NE_EXPR, type); }
+ (if (known_eq (off, 0))
+ { constant_boolean_node (cmp == EQ_EXPR, type); }))))))))
/* Equality compare simplifications from fold_binary */
(for cmp (eq ne)
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/forwprop-38.c
b/gcc/testsuite/gcc.dg/tree-ssa/forwprop-38.c
new file mode 100644
index 00000000000..e016c825b3c
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/forwprop-38.c
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-options "-O -fdump-tree-forwprop1" } */
+
+struct A { int a[1]; };
+
+void f (struct A *p)
+{
+ void *q = p->a;
+ if (p != q)
+ __builtin_abort ();
+}
+
+/* { dg-final { scan-tree-dump-not "abort" "forwprop1" } } */
--
2.16.4
