Mailing List Archive

[xen master] lib: move muldiv64()
commit b3de22dda782af06e625b513cc3cccb98c1635c6
Author: Jan Beulich <jbeulich@suse.com>
AuthorDate: Fri Apr 16 14:41:48 2021 +0200
Commit: Jan Beulich <jbeulich@suse.com>
CommitDate: Fri Apr 16 14:41:48 2021 +0200

lib: move muldiv64()

Make this a separate archive member under lib/. While doing so, don't
move latently broken x86 assembly though: Fix the constraints, such
that properly extending inputs to 64-bit won't just be a side effect of
needing to copy registers, and such that we won't fail to clobber %rdx.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Roger Pau Monné <roger.pau@citrix.com>
---
xen/common/lib.c | 29 -----------------------------
xen/lib/Makefile | 1 +
xen/lib/muldiv64.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 45 insertions(+), 29 deletions(-)

diff --git a/xen/common/lib.c b/xen/common/lib.c
index f5ca179a0a..5b8f49153d 100644
--- a/xen/common/lib.c
+++ b/xen/common/lib.c
@@ -393,35 +393,6 @@ s64 __ldivmod_helper(s64 a, s64 b, s64 *r)
}
#endif /* BITS_PER_LONG == 32 */

-/* Compute with 96 bit intermediate result: (a*b)/c */
-uint64_t muldiv64(uint64_t a, uint32_t b, uint32_t c)
-{
-#ifdef CONFIG_X86
- asm ( "mul %%rdx; div %%rcx" : "=a" (a) : "0" (a), "d" (b), "c" (c) );
- return a;
-#else
- union {
- uint64_t ll;
- struct {
-#ifdef WORDS_BIGENDIAN
- uint32_t high, low;
-#else
- uint32_t low, high;
-#endif
- } l;
- } u, res;
- uint64_t rl, rh;
-
- u.ll = a;
- rl = (uint64_t)u.l.low * (uint64_t)b;
- rh = (uint64_t)u.l.high * (uint64_t)b;
- rh += (rl >> 32);
- res.l.high = rh / c;
- res.l.low = (((rh % c) << 32) + (rl & 0xffffffff)) / c;
- return res.ll;
-#endif
-}
-
/*
* Local variables:
* mode: C
diff --git a/xen/lib/Makefile b/xen/lib/Makefile
index 1c2227cbfc..0b274583ef 100644
--- a/xen/lib/Makefile
+++ b/xen/lib/Makefile
@@ -4,6 +4,7 @@ lib-y += bsearch.o
lib-y += ctors.o
lib-y += ctype.o
lib-y += list-sort.o
+lib-y += muldiv64.o
lib-y += parse-size.o
lib-y += rbtree.o
lib-y += sort.o
diff --git a/xen/lib/muldiv64.c b/xen/lib/muldiv64.c
new file mode 100644
index 0000000000..78177ce616
--- /dev/null
+++ b/xen/lib/muldiv64.c
@@ -0,0 +1,44 @@
+#include <xen/lib.h>
+
+/* Compute with 96 bit intermediate result: (a*b)/c */
+uint64_t muldiv64(uint64_t a, uint32_t b, uint32_t c)
+{
+#ifdef CONFIG_X86
+ asm ( "mulq %1; divq %2" : "+a" (a)
+ : "rm" ((uint64_t)b), "rm" ((uint64_t)c)
+ : "rdx" );
+
+ return a;
+#else
+ union {
+ uint64_t ll;
+ struct {
+#ifdef WORDS_BIGENDIAN
+ uint32_t high, low;
+#else
+ uint32_t low, high;
+#endif
+ } l;
+ } u, res;
+ uint64_t rl, rh;
+
+ u.ll = a;
+ rl = (uint64_t)u.l.low * (uint64_t)b;
+ rh = (uint64_t)u.l.high * (uint64_t)b;
+ rh += (rl >> 32);
+ res.l.high = rh / c;
+ res.l.low = (((rh % c) << 32) + (rl & 0xffffffff)) / c;
+
+ return res.ll;
+#endif
+}
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * tab-width: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
--
generated by git-patchbot for /home/xen/git/xen.git#master