match.pd: Simplify (t * u) / (t * v) [PR112994]

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.

2023-12-14  Jakub Jelinek  <jakub@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.

diff --git a/gcc/match.pd b/gcc/match.pd
index 5954828655558109fdb8b27e7b869a11da801f48..562880aee4c23150ff09aa853189e5fad6670321 100644 (file)
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -961,7 +961,23 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
       (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
 (for div (trunc_div exact_div)

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr112994-2.c b/gcc/testsuite/gcc.dg/tree-ssa/pr112994-2.c
new file mode 100644 (file)
index 0000000..f78a72f
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr112994-2.c
@@ -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); }