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tree-optimization/94234 - add pattern for ptr-diff on addresses with same offset 

2020-08-19  Feng Xue  <fxue@os.amperecomputing.com>

gcc/
	PR tree-optimization/94234
	* match.pd ((PTR_A + OFF) - (PTR_B + OFF)) -> (PTR_A - PTR_B): New
	simplification.

gcc/testsuite/
	PR tree-optimization/94234
	* gcc.dg/pr94234-1.c: New test.
This commit is contained in:
Feng Xue 2020-06-01 11:57:35 +08:00
parent 1e235788bb
commit 459f6f68a7
2 changed files with 18 additions and 0 deletions
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3
gcc/match.pd
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@ -2549,6 +2549,9 @@ 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 @2) (pointer_plus @1 @2))
(pointer_diff @0 @1))
(simplify
(pointer_diff (pointer_plus @@0 @1) (pointer_plus @0 @2))
/* The second argument of pointer_plus must be interpreted as signed, and

15
gcc/testsuite/gcc.dg/pr94234-1.c Normal file
View File

@ -0,0 +1,15 @@
/* { dg-do compile } */
/* { dg-options "-O2 -fdump-tree-forwprop1" } */
typedef __INTPTR_TYPE__ ssize_t;
typedef __PTRDIFF_TYPE__ ptrdiff_t;
ptrdiff_t foo (char *a, ssize_t n, ssize_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 "forwprop1" } } */