Hi!
On top of the previously posted patch, this simplifies say (x * 16) / (x * 4)
into 4. Unlike the previous pattern, this is something we didn't fold
previously on GENERIC, so I think it shouldn't be all wrapped with #if
GIMPLE. The question whether there should be fold_overflow_warning for the
TYPE_OVERFLOW_UNDEFINED case remains.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk
(with or without fold_overflow_warning)?
2023-12-13 Jakub Jelinek <ja...@redhat.com>
PR tree-optimization/112994
* match.pd ((t * u) / (t * v) -> (u / v)): New simplification.
* gcc.dg/tree-ssa/pr112994-2.c: New test.
--- gcc/match.pd.jj 2023-12-13 18:43:51.277839661 +0100
+++ gcc/match.pd 2023-12-13 18:43:45.891913683 +0100
@@ -962,6 +960,23 @@ (define_operator_list SYNC_FETCH_AND_AND
&& range_op_handler (MULT_EXPR).overflow_free_p (vr0, vr1))
(mult @0 (div! @1 @2))))
#endif
+ )))
+ /* Simplify (t * u) / (t * v) -> (u / v) if u is multiple of v. */
+ (simplify
+ (div (mult @0 INTEGER_CST@1) (mult @0 INTEGER_CST@2))
+ (if (INTEGRAL_TYPE_P (type)
+ && wi::multiple_of_p (wi::to_widest (@1), wi::to_widest (@2), SIGNED))
+ (if (TYPE_OVERFLOW_UNDEFINED (type) && !TYPE_OVERFLOW_SANITIZED (type))
+ (div @1 @2)
+#if GIMPLE
+ (with {value_range vr0, vr1, vr2;}
+ (if (get_range_query (cfun)->range_of_expr (vr0, @0)
+ && get_range_query (cfun)->range_of_expr (vr1, @1)
+ && get_range_query (cfun)->range_of_expr (vr2, @2)
+ && range_op_handler (MULT_EXPR).overflow_free_p (vr0, vr1)
+ && range_op_handler (MULT_EXPR).overflow_free_p (vr0, vr2))
+ (div @1 @2)))
+#endif
))))
#if GIMPLE
--- gcc/testsuite/gcc.dg/tree-ssa/pr112994-2.c.jj 2023-12-13
19:07:20.882475735 +0100
+++ gcc/testsuite/gcc.dg/tree-ssa/pr112994-2.c 2023-12-13 19:07:02.597726855
+0100
@@ -0,0 +1,15 @@
+/* PR tree-optimization/112994 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+/* { dg-final { scan-tree-dump-times "return 2;" 3 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "return 7;" 3 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "return -7;" 2 "optimized" } } */
+
+int f1 (int x) { return (x * 4) / (x * 2); }
+int f2 (int x) { return (x * 56) / (x * 8); }
+int f3 (int x) { return (x * 56) / (x * -8); }
+int f4 (int x) { int y = x * 4; return y / (x * 2); }
+int f5 (int x) { int y = x * 56; return y / (x * 8); }
+int f6 (int x) { int y = x * 56; return y / (x * -8); }
+unsigned f7 (unsigned x) { if (x > ~0U / 4) __builtin_unreachable (); unsigned
y = x * 4; return y / (x * 2); }
+unsigned f8 (unsigned x) { if (x > ~0U / 56) __builtin_unreachable ();
unsigned y = x * 56; return y / (x * 8); }
Jakub
