Gcc 3.1 (-O) now generates broken inline code for memset in some cases.
This broke newfs (newfs left some garbage in a bitmap). The ASM for: #include <string.h> int x, foo[100]; main() { memset(&foo[0], 0, x); } is (at least if you have fixed function alignment): .file "z.c" .text .p2align 2,,3 .globl main .type main,@function main: pushl %ebp movl %esp, %ebp pushl %edi pushl %eax movl x, %ecx xorl %eax, %eax shrl $2, %ecx movl $foo, %edi cld rep stosl andl $-16, %esp <-- the lower bits of `len' should be loaded near here testl $2, %edi <-- this seems to be meant to test the 2^1 bit in `len' (not alignment of the pointer like it actually does). %edi is the wrong register for holding the bits, since it is still needed for the pointer. je .L2 stosw .L2: testl $1, %edi <-- similarly for the 2^0 bit. je .L3 stosb .L3: movl -4(%ebp), %edi leave ret .Lfe1: .size main,.Lfe1-main .comm foo,400,32 .comm x,4,4 .ident "GCC: (GNU) 3.1 [FreeBSD] 20020509 (prerelease)" This seems to only result in (len % 3) bytes not being cleared, since gcc doesn't seem to use the builtin memset unless it knows that the pointer is aligned. If %edi could be misaligned, then too many bytes would be set. Submitted by: BDE
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2020-12-20 02:59:44 +00:00
svn path=/head/; revision=97826
@ -19,6 +19,8 @@ along with GCC; see the file COPYING. If not, write to the Free
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Software Foundation, 59 Temple Place - Suite 330, Boston, MA
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02111-1307, USA. */
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/* $FreeBSD$ */
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#include "config.h"
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#include "system.h"
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#include "machmode.h"
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@ -2194,6 +2196,11 @@ expand_builtin_memset (exp, target, mode)
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len_rtx = expand_expr (len, NULL_RTX, VOIDmode, 0);
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/* Give up for non-constant lengths. They are broken on at least
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i386's. */
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if (GET_CODE (len_rtx) != CONST_INT)
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return 0;
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dest_mem = get_memory_rtx (dest);
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set_mem_align (dest_mem, dest_align);
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dest_addr = clear_storage (dest_mem, len_rtx);
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