match.pd has a rule to simplify an extension, operation and truncation
back to the original type:
(simplify
(convert (op:s@0 (convert1?@3 @1) (convert2?@4 @2)))
Currently it handles cases in which @2 is an INTEGER_CST, but it
also works for POLY_INT_CSTs.[*]
For INTEGER_CST it doesn't matter whether we test @2 or @4,
but for POLY_INT_CST it is possible to have unfolded (convert …)s.
Originally I saw this leading to some bad ivopts decisions, because
we weren't folding away redundancies from candidate iv expressions.
It's also possible to test the fold directly using the SVE ACLE.
[*] Not all INTEGER_CST rules work for POLY_INT_CSTs, since extensions
don't necessarily distribute over the internals of the POLY_INT_CST.
But in this case that isn't an issue.
gcc/
* match.pd: Simplify an extend-operate-truncate sequence involving
a POLY_INT_CST.
gcc/testsuite/
* gcc.target/aarch64/sve/acle/general/cntb_1.c: New test.
&& (types_match (@1, @2)
/* Or the second operand is const integer or converted const
integer from valueize. */
- || TREE_CODE (@2) == INTEGER_CST))
+ || poly_int_tree_p (@4)))
(if (TYPE_OVERFLOW_WRAPS (TREE_TYPE (@1)))
(op @1 (convert @2))
(with { tree utype = unsigned_type_for (TREE_TYPE (@1)); }
--- /dev/null
+/* { dg-options "-O -fdump-tree-optimized" } */
+
+#include <arm_sve.h>
+
+unsigned int
+foo (unsigned int x)
+{
+ unsigned long tmp = x;
+ tmp += svcntb ();
+ x = tmp;
+ return x - svcntb ();
+}
+
+/* { dg-final { scan-tree-dump-not { POLY_INT_CST } optimized } } */