Try testcase below the sig.
This causes nearly one thousand calls to memcpy in my kernel
(not an allyesconfig one):
# objdump -d vmlinux | grep -F '<memcpy>' | wc -l
959
# gcc -O2 -c t.c
# objdump -r -d t.o
t.o: file format elf32-i386
Disassembly of section .text:
00000000 <f3>:
0: 55 push %ebp
1: 89 e5 mov %esp,%ebp
3: 83 ec 0c sub $0xc,%esp
6: 6a 03 push $0x3
8: ff 75 0c pushl 0xc(%ebp)
b: ff 75 08 pushl 0x8(%ebp)
e: e8 fc ff ff ff call f <f3+0xf>
f: R_386_PC32 memcpy
13: 83 c4 10 add $0x10,%esp
16: c9 leave
17: c3 ret
00000018 <f3b>:
18: 55 push %ebp
19: 89 e5 mov %esp,%ebp
1b: 8b 55 0c mov 0xc(%ebp),%edx
1e: 66 8b 02 mov (%edx),%ax
21: 8b 4d 08 mov 0x8(%ebp),%ecx
24: 66 89 01 mov %ax,(%ecx)
27: 8a 42 02 mov 0x2(%edx),%al
2a: 88 41 02 mov %al,0x2(%ecx)
2d: c9 leave
2e: c3 ret
2f: 90 nop
00000030 <f3k>:
30: 55 push %ebp
31: 89 e5 mov %esp,%ebp
33: 57 push %edi
34: 56 push %esi
35: 8b 7d 08 mov 0x8(%ebp),%edi
38: 8b 75 0c mov 0xc(%ebp),%esi
3b: b9 ee 02 00 00 mov $0x2ee,%ecx
40: f3 a5 repz movsl %ds:(%esi),%es:(%edi)
42: 5e pop %esi
43: 5f pop %edi
44: c9 leave
45: c3 ret
--
vda
typedef unsigned int size_t;
static inline void * __memcpy(void * to, const void * from, size_t n)
{
int d0, d1, d2;
__asm__ __volatile__(
"rep ; movsl\n\t"
"testb $2,%b4\n\t"
"je 1f\n\t"
"movsw\n"
"1:\ttestb $1,%b4\n\t"
"je 2f\n\t"
"movsb\n"
"2:"
: "=&c" (d0), "=&D" (d1), "=&S" (d2)
:"0" (n/4), "q" (n),"1" ((long) to),"2" ((long) from)
: "memory");
return (to);
}
/*
* This looks horribly ugly, but the compiler can optimize it totally,
* as the count is constant.
*/
static inline void * __constant_memcpy(void * to, const void * from, size_t n)
{
if (n <= 128)
return __builtin_memcpy(to, from, n);
#define COMMON(x) \
__asm__ __volatile__( \
"rep ; movsl" \
x \
: "=&c" (d0), "=&D" (d1), "=&S" (d2) \
: "0" (n/4),"1" ((long) to),"2" ((long) from) \
: "memory");
{
int d0, d1, d2;
switch (n % 4) {
case 0: COMMON(""); return to;
case 1: COMMON("\n\tmovsb"); return to;
case 2: COMMON("\n\tmovsw"); return to;
default: COMMON("\n\tmovsw\n\tmovsb"); return to;
}
}
#undef COMMON
}
#define memcpy(t, f, n) \
(__builtin_constant_p(n) ? \
__constant_memcpy((t),(f),(n)) : \
__memcpy((t),(f),(n)))
int f3(char *a, char *b) { memcpy(a,b,3); }
int f3b(char *a, char *b) { __builtin_memcpy(a,b,3); }
int f3k(char *a, char *b) { memcpy(a,b,3000); }
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