Use stosl in memset; makes boot time bearable

2011-09-01 10:41:21 -04:00 · 2011-09-01 10:41:21 -04:00 · d0f3efca65
parent e25b74ca80
commit d0f3efca65
2 changed files with 14 additions and 1 deletions
--- a/string.c
+++ b/string.c
@ -4,7 +4,11 @@
 void*
 memset(void *dst, int c, uint n)
 {
-  stosb(dst, c, n);
+  if ((int)dst%4 == 0 && n%4 == 0){
+    c &= 0xFF;
+    stosl(dst, (c<<24)|(c<<16)|(c<<8)|c, n/4);
+  } else
+    stosb(dst, c, n);
  return dst;
 }

--- a/x86.h
+++ b/x86.h
@ -48,6 +48,15 @@ stosb(void *addr, int data, int cnt)
               "memory", "cc");
 }

+static inline void
+stosl(void *addr, int data, int cnt)
+{
+  asm volatile("cld; rep stosl" :
+               "=D" (addr), "=c" (cnt) :
+               "0" (addr), "1" (cnt), "a" (data) :
+               "memory", "cc");
+}
+
 struct segdesc;

 static inline void