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* [gcc r13-2900] range-ops: Calculate the popcount of a singleton.
@ 2022-09-27 15:02 Aldy Hernandez
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From: Aldy Hernandez @ 2022-09-27 15:02 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:001c60ccfeaf9a480a56203418af804ad42e88b9
commit r13-2900-g001c60ccfeaf9a480a56203418af804ad42e88b9
Author: Aldy Hernandez <aldyh@redhat.com>
Date: Tue Sep 27 10:30:00 2022 +0200
range-ops: Calculate the popcount of a singleton.
The legacy popcount folding didn't actually fold singleton ranges.
I don't think anyone noticed because there are match.pd patterns that
fold __builtin_popcount using the global nonzero bits set by CCP.
It's good form to handle this, even without CCP's help.
Tested on x86-64 Linux.
gcc/ChangeLog:
* gimple-range-op.cc (cfn_popcount): Calculate the popcount of a
singleton.
gcc/testsuite/ChangeLog:
* gcc.dg/tree-ssa/popcount6b.c: New test.
Diff:
---
gcc/gimple-range-op.cc | 8 ++++++++
gcc/testsuite/gcc.dg/tree-ssa/popcount6b.c | 6 ++++++
2 files changed, 14 insertions(+)
diff --git a/gcc/gimple-range-op.cc b/gcc/gimple-range-op.cc
index d7c6dfa933d..3f5e5852e5a 100644
--- a/gcc/gimple-range-op.cc
+++ b/gcc/gimple-range-op.cc
@@ -397,6 +397,14 @@ public:
{
if (lh.undefined_p ())
return false;
+ // Calculating the popcount of a singleton is trivial.
+ if (lh.singleton_p ())
+ {
+ wide_int nz = lh.get_nonzero_bits ();
+ wide_int pop = wi::shwi (wi::popcount (nz), TYPE_PRECISION (type));
+ r.set (type, pop, pop);
+ return true;
+ }
// __builtin_ffs* and __builtin_popcount* return [0, prec].
int prec = TYPE_PRECISION (lh.type ());
// If arg is non-zero, then ffs or popcount are non-zero.
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/popcount6b.c b/gcc/testsuite/gcc.dg/tree-ssa/popcount6b.c
new file mode 100644
index 00000000000..90336ecb070
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/popcount6b.c
@@ -0,0 +1,6 @@
+// { dg-do compile }
+// { dg-options "-O2 -fdump-tree-evrp -fno-tree-ccp" }
+
+#include "popcount6.c"
+
+// { dg-final { scan-tree-dump "return 1;" "evrp" } }
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