[PATCH] MATCH: Maybe expand (T)(A + C1) * C2 and (T)(A + C1) * C2 + C3 [PR109393]

[Manolis Tsamis]

The original motivation for this pattern was that the following function does
not fold to 'return 1':

int foo(int *a, int j)
{
  int k = j - 1;
  return a[j - 1] == a[k];
}

The expression ((unsigned long) (X +- C1) * C2) appears frequently as part of
address calculations (e.g. arrays). These patterns help fold and simplify more
expressions.

        PR tree-optimization/109393

gcc/ChangeLog:

        * match.pd: Add new patterns for ((T)(A +- CST1)) * CST2 and
          ((T)(A +- CST1)) * CST2 + CST3.

gcc/testsuite/ChangeLog:

        * gcc.dg/pr109393.c: New test.

Signed-off-by: Manolis Tsamis <manolis.tsa...@vrull.eu>
---

 gcc/match.pd                    | 30 ++++++++++++++++++++++++++++++
 gcc/testsuite/gcc.dg/pr109393.c | 16 ++++++++++++++++
 2 files changed, 46 insertions(+)
 create mode 100644 gcc/testsuite/gcc.dg/pr109393.c

diff --git a/gcc/match.pd b/gcc/match.pd
index d401e7503e6..13c828ba70d 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -3650,6 +3650,36 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
        (plus (convert @0) (op @2 (convert @1))))))
 #endif
 
+/* ((T)(A + CST1)) * CST2 + CST3
+     -> ((T)(A) * CST2) + ((T)CST1 * CST2 + CST3)
+   Where (A + CST1) doesn't need to have a single use.  */
+#if GIMPLE
+  (for op (plus minus)
+   (simplify
+    (plus (mult (convert:s (op @0 INTEGER_CST@1)) INTEGER_CST@2) INTEGER_CST@3)
+     (if (TREE_CODE (TREE_TYPE (@0)) == INTEGER_TYPE
+         && TREE_CODE (type) == INTEGER_TYPE
+         && TYPE_PRECISION (type) > TYPE_PRECISION (TREE_TYPE (@0))
+         && TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (@0))
+         && !TYPE_OVERFLOW_SANITIZED (TREE_TYPE (@0))
+         && TYPE_OVERFLOW_WRAPS (type))
+       (op (mult @2 (convert @0)) (plus (mult @2 (convert @1)) @3)))))
+#endif
+
+/* ((T)(A + CST1)) * CST2 -> ((T)(A) * CST2) + ((T)CST1 * CST2)  */
+#if GIMPLE
+  (for op (plus minus)
+   (simplify
+    (mult (convert:s (op:s @0 INTEGER_CST@1)) INTEGER_CST@2)
+     (if (TREE_CODE (TREE_TYPE (@0)) == INTEGER_TYPE
+         && TREE_CODE (type) == INTEGER_TYPE
+         && TYPE_PRECISION (type) > TYPE_PRECISION (TREE_TYPE (@0))
+         && TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (@0))
+         && !TYPE_OVERFLOW_SANITIZED (TREE_TYPE (@0))
+         && TYPE_OVERFLOW_WRAPS (type))
+       (op (mult @2 (convert @0)) (mult @2 (convert @1))))))
+#endif
+
 /* (T)(A) +- (T)(B) -> (T)(A +- B) only when (A +- B) could be simplified
    to a simple value.  */
   (for op (plus minus)
diff --git a/gcc/testsuite/gcc.dg/pr109393.c b/gcc/testsuite/gcc.dg/pr109393.c
new file mode 100644
index 00000000000..e9051273672
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr109393.c
@@ -0,0 +1,16 @@
+/* PR tree-optimization/109393 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+/* { dg-final { scan-tree-dump-times "return 1;" 2 "optimized" } } */
+
+int foo(int *a, int j)
+{
+  int k = j - 1;
+  return a[j - 1] == a[k];
+}
+
+int bar(int *a, int j)
+{
+  int k = j - 1;
+  return (&a[j + 1] - 2) == &a[k];
+}
-- 
2.34.1