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Fix spurious page faults by double word aligning the source and not the 

destination. Thank's to Ian Dall for this fix.
This commit is contained in:
matthias 1999-06-06 19:49:11 +00:00
parent 7cdfe2dbc5
commit bb36354c10
1 changed files with 11 additions and 12 deletions
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23
lib/libc/arch/ns32k/string/strcpy.S
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@ -1,4 +1,4 @@
/* $NetBSD: strcpy.S,v 1.3 1998/04/03 22:58:10 matthias Exp $ */ /* $NetBSD: strcpy.S,v 1.4 1999/06/06 19:49:11 matthias Exp $ */
/* /*
* Written by Randy Hyde, 1993 * Written by Randy Hyde, 1993
@ -8,7 +8,7 @@
#include <machine/asm.h> #include <machine/asm.h>
#if defined(LIBC_SCCS) #if defined(LIBC_SCCS)
RCSID("$NetBSD: strcpy.S,v 1.3 1998/04/03 22:58:10 matthias Exp $") RCSID("$NetBSD: strcpy.S,v 1.4 1999/06/06 19:49:11 matthias Exp $")
#endif #endif
/* /*
@ -23,16 +23,15 @@ KENTRY(strcpy, 8)
movd B_ARG0,r2 movd B_ARG0,r2
/* /*
* First begin by seeing if we can doubleword align the * We need to double word align the src (R1). When we read
* pointers. The following code only aligns the pointer in R2. * by double words we can read potentially up to 3 bytes
* If the L.O. two bits of R1 do not match, it's going to run * past the null terminating byte. We can avoid spurious page
* slower but there is nothing we can do about that. Better to * faults by double word aligning the source. It also runs
* have at least one of them double word aligned rather than * faster. IWD
* neither.
*/ */
movqd 3,r3 movqd 3,r3
andd r2,r3 andd r1,r3
0: casew 1f(pc)[r3:w] 0: casew 1f(pc)[r3:w]
1: .word 5f-0b 1: .word 5f-0b
@ -61,13 +60,13 @@ KENTRY(strcpy, 8)
addqd 1,r2 addqd 1,r2
/* /*
* Okay, when we get down here R2 points at a double word * Okay, when we get down here R1 points at a double word
* aligned destination block of bytes, R1 points at another * aligned source block of bytes, R2 points at the destination
* block of bytes (typically, though not always double word * block of bytes (typically, though not always double word
* aligned). * aligned).
* This guy processes four bytes at a time and checks for the * This guy processes four bytes at a time and checks for the
* zero terminating byte amongst the bytes in the double word. * zero terminating byte amongst the bytes in the double word.
* This algorithm is de to Dave Rand. * This algorithm is due to Dave Rand.
* *
* Sneaky test for zero amongst four bytes: * Sneaky test for zero amongst four bytes:
* *