The PR notices we fail to simplify
a_4 = &x_3(D)->data;
b_5 = x_3(D) + 16;
_1 = b_5 - a_4;
together with the enabler handling ADDR_EXPR leafs in separate
stmts in match.pd the suggested patterns work.
Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.
PR tree-optimization/89317
* match.pd ((p + b) - &p->c -> b - offsetof(c)): New patterns.
* gcc.dg/tree-ssa/pr89317.c: New testcase.
---
gcc/match.pd | 11 +++++++++++
gcc/testsuite/gcc.dg/tree-ssa/pr89317.c | 13 +++++++++++++
2 files changed, 24 insertions(+)
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr89317.c
diff --git a/gcc/match.pd b/gcc/match.pd
index 046ea2cdef4..ba83c69734f 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -2451,6 +2451,17 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
(with { poly_int64 diff; }
(if (ptr_difference_const (@0, @2, &diff))
(plus { build_int_cst_type (type, diff); } (convert (minus @1 @3))))))
+/* (p + b) - &p->d -> offsetof (*p, d) + b */
+(simplify
+ (pointer_diff (pointer_plus @0 @1) ADDR_EXPR@2)
+ (with { poly_int64 diff; }
+ (if (ptr_difference_const (@0, @2, &diff))
+ (plus { build_int_cst_type (type, diff); } (convert @1)))))
+(simplify
+ (pointer_diff ADDR_EXPR@0 (pointer_plus @1 @2))
+ (with { poly_int64 diff; }
+ (if (ptr_difference_const (@0, @1, &diff))
+ (minus { build_int_cst_type (type, diff); } (convert @2)))))
/* Canonicalize (T *)(ptr - ptr-cst) to &MEM[ptr + -ptr-cst]. */
(simplify
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr89317.c
b/gcc/testsuite/gcc.dg/tree-ssa/pr89317.c
new file mode 100644
index 00000000000..0d0a049454f
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr89317.c
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-options "-O -fdump-tree-ccp1" } */
+
+struct b { int data[16]; };
+
+int foo (struct b *x)
+{
+ int *a = x->data;
+ int *b = ((int*)x) + 4;
+ return b - a;
+}
+
+/* { dg-final { scan-tree-dump "return 4;" "ccp1" } } */
--
2.35.3
