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

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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.
This commit is contained in:
Jakub Jelinek 2023-12-14 12:06:59 +01:00
parent 90c9403f89
commit 2c92551405
2 changed files with 32 additions and 1 deletions
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18
gcc/match.pd
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@ -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)

15
gcc/testsuite/gcc.dg/tree-ssa/pr112994-2.c Normal file
View file

@ -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); }