[src/trunk]: src/sys/external/bsd/drm2/include/linux Split bitmap_set/clear i...

[riastradh <riastradh%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/999db2864eff
branches:  trunk
changeset: 835412:999db2864eff
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Mon Aug 27 14:52:16 2018 +0000

description:
Split bitmap_set/clear into begin/middle/end sections.

For clarity and speed.  Largely from uwe@ with tweaks from me.

diffstat:

 sys/external/bsd/drm2/include/linux/bitmap.h |  54 ++++++++++++++++++++-------
 1 files changed, 39 insertions(+), 15 deletions(-)

diffs (81 lines):

diff -r 706c76134a61 -r 999db2864eff sys/external/bsd/drm2/include/linux/bitmap.h
--- a/sys/external/bsd/drm2/include/linux/bitmap.h      Mon Aug 27 14:51:55 2018 +0000
+++ b/sys/external/bsd/drm2/include/linux/bitmap.h      Mon Aug 27 14:52:16 2018 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: bitmap.h,v 1.7 2018/08/27 14:51:05 riastradh Exp $     */
+/*     $NetBSD: bitmap.h,v 1.8 2018/08/27 14:52:16 riastradh Exp $     */
 
 /*-
  * Copyright (c) 2018 The NetBSD Foundation, Inc.
@@ -105,16 +105,28 @@
 {
        const size_t bpl = NBBY * sizeof(*bitmap);
        unsigned long *p = bitmap + startbit/bpl;
-       unsigned long mask;
-       unsigned sz;
+       unsigned initial = startbit%bpl;
 
-       for (sz = bpl - (startbit%bpl), mask = ~0UL << (startbit%bpl);
-            nbits >= sz;
-            nbits -= sz, sz = bpl, mask = ~0UL)
-               *p++ |= mask;
+       /* Handle an initial odd word if any.  */
+       if (initial) {
+               /* Does the whole thing fit in a single word?  */
+               if (nbits <= bpl - initial) {
+                       /* Yes: just set nbits starting at initial.  */
+                       *p |= ~(~0ULL << nbits) << initial;
+                       return;
+               }
+               /* Nope: set all bits above initial, and advance.  */
+               *p++ |= ~0ULL << initial;
+               nbits -= bpl - initial;
+       }
 
+       /* Set the middle part to all bits 1.  */
+       for (; nbits >= bpl; nbits -= bpl)
+               *p++ = ~0UL;
+
+       /* Handle a final odd word if any by setting its low nbits.  */
        if (nbits)
-               *p |= mask & ~(~0UL << (nbits + bpl - sz));
+               *p |= ~(~0ULL << nbits);
 }
 
 /*
@@ -128,16 +140,28 @@
 {
        const size_t bpl = NBBY * sizeof(*bitmap);
        unsigned long *p = bitmap + startbit/bpl;
-       unsigned long mask;
-       unsigned sz;
+       unsigned initial = startbit%bpl;
 
-       for (sz = bpl - (startbit%bpl), mask = ~(~0UL << (startbit%bpl));
-            nbits >= sz;
-            nbits -= sz, sz = bpl, mask = 0UL)
-               *p++ &= mask;
+       /* Handle an initial odd word if any.  */
+       if (initial) {
+               /* Does the whole thing fit in a single word?  */
+               if (nbits <= bpl - initial) {
+                       /* Yes: just clear nbits starting at initial.  */
+                       *p &= ~(~(~0ULL << nbits) << initial);
+                       return;
+               }
+               /* Nope: clear all bits above initial, and advance.  */
+               *p++ &= ~(~0ULL << initial);
+               nbits -= bpl - initial;
+       }
 
+       /* Zero the middle part.  */
+       for (; nbits >= bpl; nbits -= bpl)
+               *p++ = 0UL;
+
+       /* Handle a final odd word if any by clearing its low nbits.  */
        if (nbits)
-               *p &= mask | (~0UL << (nbits + bpl - sz));
+               *p &= ~0ULL << nbits;
 }
 
 /*