This patch is meant to add match rules to simplify patterns as:
o. (pointer + offset_a) - (pointer + offset_b) -> (ptrdiff_t) (offset_a -
offset_b)
o. (pointer_a + offset) - (pointer_b + offset) -> (pointer_a - pointer_b)
Bootstrapped/regtested on x86_64-linux and aarch64-linux.
Feng
---
2020-06-01 Feng Xue <f...@os.amperecomputing.com>
gcc/
PR tree-optimization/94234
* match.pd ((PTR + A) - (PTR + B)) -> (ptrdiff_t)(A - B): New
simplification.
* ((PTR_A + O) - (PTR_B + O)) -> (PTR_A - PTR_B): New simplification.
gcc/testsuite/
PR tree-optimization/94234
* gcc.dg/pr94234.c: New test.
---
gcc/match.pd | 19 +++++++++----------
gcc/testsuite/gcc.dg/pr94234.c | 24 ++++++++++++++++++++++++
2 files changed, 33 insertions(+), 10 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/pr94234.c
diff --git a/gcc/match.pd b/gcc/match.pd
index 33ee1a920bf..6553be4822e 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -2515,16 +2515,15 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
&& TREE_CODE (@2) == INTEGER_CST
&& tree_int_cst_sign_bit (@2) == 0))
(minus (convert @1) (convert @2)))))
- (simplify
- (pointer_diff (pointer_plus @@0 @1) (pointer_plus @0 @2))
- /* The second argument of pointer_plus must be interpreted as signed, and
- thus sign-extended if necessary. */
- (with { tree stype = signed_type_for (TREE_TYPE (@1)); }
- /* Use view_convert instead of convert here, as POINTER_PLUS_EXPR
- second arg is unsigned even when we need to consider it as signed,
- we don't want to diagnose overflow here. */
- (minus (convert (view_convert:stype @1))
- (convert (view_convert:stype @2)))))))
+ (simplify
+ (pointer_diff (pointer_plus@3 @0 @1) (pointer_plus @0 @2))
+ (if (TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (@3)))
+ (convert (minus @1 @2))))
+ (simplify
+ (pointer_diff (pointer_plus@3 @0 @2) (pointer_plus @1 @2))
+ (if (TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (@3))
+ && !integer_zerop (@2))
+ (pointer_diff @0 @1)))))
/* (A * C) +- (B * C) -> (A+-B) * C and (A * C) +- A -> A * (C+-1).
Modeled after fold_plusminus_mult_expr. */
diff --git a/gcc/testsuite/gcc.dg/pr94234.c b/gcc/testsuite/gcc.dg/pr94234.c
new file mode 100644
index 00000000000..ef9076c80da
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr94234.c
@@ -0,0 +1,24 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-ccp1" } */
+
+typedef __SIZE_TYPE__ size_t;
+typedef __PTRDIFF_TYPE__ ptrdiff_t;
+
+ptrdiff_t foo (char *a, size_t n)
+{
+ char *b1 = a + 8 * n;
+ char *b2 = a + 8 * (n - 1);
+
+ return b1 - b2;
+}
+
+ptrdiff_t goo (char *a, size_t n, size_t m)
+{
+ char *b1 = a + 8 * n;
+ char *b2 = a + 8 * (n + 1);
+
+ return (b1 + m) - (b2 + m);
+}
+
+/* { dg-final { scan-tree-dump-times "return 8;" 1 "ccp1" } } */
+/* { dg-final { scan-tree-dump-times "return -8;" 1 "ccp1" } } */
From 160eaeb151197844005837dc4b8e1e27bb6dfadf Mon Sep 17 00:00:00 2001
From: Feng Xue <f...@os.amperecomputing.com>
Date: Mon, 1 Jun 2020 11:57:35 +0800
Subject: [PATCH] tree-optimization/94234 - add ptr-diff pattern for addresses
with same base or offset
2020-06-01 Feng Xue <f...@os.amperecomputing.com>
gcc/
PR tree-optimization/94234
* match.pd ((PTR + A) - (PTR + B)) -> (ptrdiff_t)(A - B): New
simplification.
* ((PTR_A + O) - (PTR_B + O)) -> (PTR_A - PTR_B): New simplification.
gcc/testsuite/
PR tree-optimization/94234
* gcc.dg/pr94234.c: New test.
---
gcc/match.pd | 19 +++++++++----------
gcc/testsuite/gcc.dg/pr94234.c | 24 ++++++++++++++++++++++++
2 files changed, 33 insertions(+), 10 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/pr94234.c
diff --git a/gcc/match.pd b/gcc/match.pd
index 33ee1a920bf..6553be4822e 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -2515,16 +2515,15 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
&& TREE_CODE (@2) == INTEGER_CST
&& tree_int_cst_sign_bit (@2) == 0))
(minus (convert @1) (convert @2)))))
- (simplify
- (pointer_diff (pointer_plus @@0 @1) (pointer_plus @0 @2))
- /* The second argument of pointer_plus must be interpreted as signed, and
- thus sign-extended if necessary. */
- (with { tree stype = signed_type_for (TREE_TYPE (@1)); }
- /* Use view_convert instead of convert here, as POINTER_PLUS_EXPR
- second arg is unsigned even when we need to consider it as signed,
- we don't want to diagnose overflow here. */
- (minus (convert (view_convert:stype @1))
- (convert (view_convert:stype @2)))))))
+ (simplify
+ (pointer_diff (pointer_plus@3 @0 @1) (pointer_plus @0 @2))
+ (if (TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (@3)))
+ (convert (minus @1 @2))))
+ (simplify
+ (pointer_diff (pointer_plus@3 @0 @2) (pointer_plus @1 @2))
+ (if (TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (@3))
+ && !integer_zerop (@2))
+ (pointer_diff @0 @1)))))
/* (A * C) +- (B * C) -> (A+-B) * C and (A * C) +- A -> A * (C+-1).
Modeled after fold_plusminus_mult_expr. */
diff --git a/gcc/testsuite/gcc.dg/pr94234.c b/gcc/testsuite/gcc.dg/pr94234.c
new file mode 100644
index 00000000000..ef9076c80da
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr94234.c
@@ -0,0 +1,24 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-ccp1" } */
+
+typedef __SIZE_TYPE__ size_t;
+typedef __PTRDIFF_TYPE__ ptrdiff_t;
+
+ptrdiff_t foo (char *a, size_t n)
+{
+ char *b1 = a + 8 * n;
+ char *b2 = a + 8 * (n - 1);
+
+ return b1 - b2;
+}
+
+ptrdiff_t goo (char *a, size_t n, size_t m)
+{
+ char *b1 = a + 8 * n;
+ char *b2 = a + 8 * (n + 1);
+
+ return (b1 + m) - (b2 + m);
+}
+
+/* { dg-final { scan-tree-dump-times "return 8;" 1 "ccp1" } } */
+/* { dg-final { scan-tree-dump-times "return -8;" 1 "ccp1" } } */
--
2.17.1
