[xen master] lib: move muldiv64()

[patchbot@xxxxxxx]

commit b3de22dda782af06e625b513cc3cccb98c1635c6
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Fri Apr 16 14:41:48 2021 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
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@xxxxxxxx>
    Acked-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
 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:
+ */
--
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