powerpc: Add support for popcnt instructions

POWER5 added popcntb, and POWER7 added popcntw and popcntd. As a first step
this patch does all the work out of line, but it would be nice to implement
them as inlines with an out of line fallback.

The performance issue with hweight was noticed when disabling SMT on a large
(192 thread) POWER7 box. The patch improves that testcase by about 8%.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 110 insertions, 0 deletions

diff --git a/arch/powerpc/lib/hweight_64.S b/arch/powerpc/lib/hweight_64.S
new file mode 100644
index 0000000..ee2320b
--- /dev/null
+++ b/arch/powerpc/lib/hweight_64.S
@@ -0,0 +1,110 @@
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright (C) IBM Corporation, 2010
+ *
+ * Author: Anton Blanchard <anton@au.ibm.com>
+ */
+#include <asm/processor.h>
+#include <asm/ppc_asm.h>
+
+/* Note: This code relies on -mminimal-toc */
+
+_GLOBAL(__arch_hweight8)
+BEGIN_FTR_SECTION
+	b .__sw_hweight8
+	nop
+	nop
+FTR_SECTION_ELSE
+	popcntb	r3,r3
+	clrldi	r3,r3,64-8
+	blr
+ALT_FTR_SECTION_END_IFCLR(CPU_FTR_POPCNTB)
+
+_GLOBAL(__arch_hweight16)
+BEGIN_FTR_SECTION
+	b .__sw_hweight16
+	nop
+	nop
+	nop
+	nop
+FTR_SECTION_ELSE
+  BEGIN_FTR_SECTION_NESTED(50)
+	popcntb r3,r3
+	srdi	r4,r3,8
+	add	r3,r4,r3
+	clrldi	r3,r3,64-8
+	blr
+  FTR_SECTION_ELSE_NESTED(50)
+	clrlwi  r3,r3,16
+	popcntw	r3,r3
+	clrldi	r3,r3,64-8
+	blr
+  ALT_FTR_SECTION_END_NESTED_IFCLR(CPU_FTR_POPCNTD, 50)
+ALT_FTR_SECTION_END_IFCLR(CPU_FTR_POPCNTB)
+
+_GLOBAL(__arch_hweight32)
+BEGIN_FTR_SECTION
+	b .__sw_hweight32
+	nop
+	nop
+	nop
+	nop
+	nop
+	nop
+FTR_SECTION_ELSE
+  BEGIN_FTR_SECTION_NESTED(51)
+	popcntb r3,r3
+	srdi	r4,r3,16
+	add	r3,r4,r3
+	srdi	r4,r3,8
+	add	r3,r4,r3
+	clrldi	r3,r3,64-8
+	blr
+  FTR_SECTION_ELSE_NESTED(51)
+	popcntw	r3,r3
+	clrldi	r3,r3,64-8
+	blr
+  ALT_FTR_SECTION_END_NESTED_IFCLR(CPU_FTR_POPCNTD, 51)
+ALT_FTR_SECTION_END_IFCLR(CPU_FTR_POPCNTB)
+
+_GLOBAL(__arch_hweight64)
+BEGIN_FTR_SECTION
+	b .__sw_hweight64
+	nop
+	nop
+	nop
+	nop
+	nop
+	nop
+	nop
+	nop
+FTR_SECTION_ELSE
+  BEGIN_FTR_SECTION_NESTED(52)
+	popcntb r3,r3
+	srdi	r4,r3,32
+	add	r3,r4,r3
+	srdi	r4,r3,16
+	add	r3,r4,r3
+	srdi	r4,r3,8
+	add	r3,r4,r3
+	clrldi	r3,r3,64-8
+	blr
+  FTR_SECTION_ELSE_NESTED(52)
+	popcntd	r3,r3
+	clrldi	r3,r3,64-8
+	blr
+  ALT_FTR_SECTION_END_NESTED_IFCLR(CPU_FTR_POPCNTD, 52)
+ALT_FTR_SECTION_END_IFCLR(CPU_FTR_POPCNTB)