From: Jakub Jelinek <jakub@redhat.com>
Date: Thu, 30 Jul 2026 07:53:50 +0000 (+0200)
Subject: match.pd: Optimize .PARITY (.BITREVERSE (x))
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=1e5dca08d72f83a6c4ea3bcd2f7cc80bdfd6fc0b;p=thirdparty%2Fgcc.git

match.pd: Optimize .PARITY (.BITREVERSE (x))

When working on the last patch, I've noticed that the parity(bswap(x))
optimization only optimizes the 16/32/64/128-bit bswaps, but not
generic _BitInt bswap, and doesn't optimize any of the bitreverses.
Both all bswap and all bitreverse builtins/ifns preserve values of all the
bits, just permute them, so parity (and popcount too) can be optimized.

2026-07-30  Jakub Jelinek  <jakub@redhat.com>

	* match.pd (parity(bswap(x)) is parity(x)): Use BSWAP BITREVERSE
	instead of BUILT_IN_BSWAP16 BUILT_IN_BSWAP32 BUILT_IN_BSWAP64
	BUILT_IN_BSWAP128.

	* gcc.dg/bitint-140.c: New test.

Reviewed-by: Richard Biener <rguenth@suse.de>
---

diff --git a/gcc/match.pd b/gcc/match.pd
index d6702f66733..3658a355c40 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -10758,8 +10758,7 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
 
 /* parity(bswap(x)) is parity(x).  */
 (for parity (PARITY)
-  (for bswap (BUILT_IN_BSWAP16 BUILT_IN_BSWAP32
-	      BUILT_IN_BSWAP64 BUILT_IN_BSWAP128)
+  (for bswap (BSWAP BITREVERSE)
     (simplify
       (parity (convert?@0 (bswap:s@1 @2)))
       (if (INTEGRAL_TYPE_P (TREE_TYPE (@0))
diff --git a/gcc/testsuite/gcc.dg/bitint-140.c b/gcc/testsuite/gcc.dg/bitint-140.c
new file mode 100644
index 00000000000..35550830d9d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/bitint-140.c
@@ -0,0 +1,17 @@
+/* { dg-do compile { target bitint575 } } */
+/* { dg-options "-O2 -fdump-tree-cplxlower1" } */
+/* { dg-final { scan-tree-dump-not "\.BSWAP \\\(" "cplxlower1" } } */
+/* { dg-final { scan-tree-dump-not "\.BITREVERSE \\\(" "cplxlower1" } } */
+/* { dg-final { scan-tree-dump-times "\.PARITY \\\(x_" 2 "cplxlower1" } } */
+
+int
+foo (unsigned _BitInt(512) x)
+{
+  return __builtin_parityg (__builtin_bswapg (x));
+}
+
+int
+bar (unsigned _BitInt(575) x)
+{
+  return __builtin_parityg (__builtin_bitreverseg (x));
+}