11 January 2017, 20:44 | #21 | |
bye
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Quote:
You need the patched binutil-2.14 which is in the toolchain: Code:
./toolchain-m68k --gcc 6 --binutils 2.14 Bebbo |
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18 January 2017, 17:33 | #22 |
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Can we see some generated code?
For reference here is a small function strcpy.c Code:
char *strcpy(char *dst, const char *src) { char *ret = dst; while(*dst++=*src++) ; return ret; } Code:
m68k-amigaos-gcc -fno-builtin -S strcpy.c -c -fverbose-asm -fomit-frame-pointer -O3 Code:
_strcpy: movel sp@(4),a0 ;# dst, dst movel sp@(8),a1 ;# src, src movel a0,d1 ;# dst, ret .even L2: moveb a1@+,d0 ;#, tmp36 moveb d0,a0@+ ;# tmp36, jne L2 ;# movel d1,d0 ;# ret, <result> rts Code:
strcpy: move.l %a2,-(%sp) |, move.l 8(%sp),%a0 | dst, dst move.l 12(%sp),%a2 | src, src move.l %a0,%a1 | dst, ivtmp.12 .L2: move.b (%a2)+,%d0 | MEM[base: src_8, offset: 4294967295B], D.1040 move.b %d0,(%a1)+ | D.1040, MEM[base: _14, offset: 0B] jne .L2 | move.l %a0,%d0 |, move.l (%sp)+,%a2 |, rts Thanks. |
18 January 2017, 20:09 | #23 |
Amigan
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I don't have libnix built yet but GCC 6.2.1 produces this:
Code:
_strcpy: move.l a2,-(sp) |, move.l a0,d0 | dst, dst move.l a0,a2 | dst, ivtmp.11 .L2: move.b (a1)+,d1 | MEM[base: src_8, offset: 4294967295B], _9 move.b d1,(a2)+ | _9, MEM[base: _14, offset: 0B] jne .L2 | move.l (sp)+,a2 |, rts |
18 January 2017, 21:15 | #24 | |
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Quote:
The code is flawed of course (as usual with GCC) and should probably be the following using register arguments as above with a0=dst a1=src (inlining would be better where possible). Code:
_strcpy: move.l a0,d0 .L2: move.b (a1)+,(a0)+ jne .L2 rts |
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19 January 2017, 13:15 | #25 |
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19 January 2017, 17:49 | #26 | |
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Quote:
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19 January 2017, 17:51 | #27 |
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19 January 2017, 22:37 | #28 |
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The code generation is flawed in comparison to what modern compilers are capable of.
Vbcc uses assembler inlines by default giving the following code for strcpy(). Code:
move.l a0,d0 .l1: move.b (a1)+,(a0)+ bne .l1 Code:
strcpy: movem.l a2-a3,-(sp) movea.l ($10,sp),a3 movea.l ($c,sp),a2 move.l a2,d0 movea.l a3,a1 addq.l #1,a3 movea.l a2,a0 addq.l #1,a2 move.b (a1),(a0) beq.b .l2 .l1: movea.l a3,a1 addq.l #1,a3 movea.l a2,a0 addq.l #1,a2 move.b (a1),(a0) bne.b .l1 .l2: movem.l (sp)+,a2-a3 rts |
20 January 2017, 01:34 | #29 |
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Wow, that's bad. I don't think even old compilers like SAS/C produce that kind of code. Just wow
I certainly know which compiler to avoid now. What a shame Last edited by Thorham; 20 January 2017 at 01:59. |
20 January 2017, 02:16 | #30 |
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It is embarrassing and frustrating. Vbcc can generate some of the best code and some of the worst. I don't know what happened here. It was generating better code in an earlier version. It is capable of using advanced instructions and addressing modes like move.b (a1)+,(a0)+ but then so is GCC. Maybe there is a fix already for some of the problems but more problems seem to creep back in with both vbcc and GCC. Too much complexity and not enough developers any more. Sad .
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20 January 2017, 02:36 | #31 |
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At least that means SAS/C isn't useless
Here's what SAS/C produces, for those who are interested. Code:
SECTION text,CODE __code: @strcopy: MOVE.L A2,-(A7) ;2f0a ___strcopy__1: MOVE.L A1,A2 ;2449 ___strcopy__2: MOVE.B (A0)+,D0 ;1018 MOVE.B D0,(A1)+ ;12c0 BNE.B ___strcopy__2 ;66fa ___strcopy__3: MOVE.L A2,D0 ;200a ___strcopy__4: MOVE.L (A7)+,A2 ;245f RTS ;4e75 __const: __strings: XDEF @strcopy END |
20 January 2017, 08:28 | #32 |
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Seems like the gcc-3.4.0 produces the most efficient code then, as it avoids saving/restoring a register to stack.
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20 January 2017, 09:45 | #33 | |
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Quote:
Code:
strcpy move.l a0,d0 .loop move.b (a0)+,(a1)+ bne.s .loop rts Code:
strcpy move.l a0,d0 .loop move.b (a0)+,(a1)+ beq.s .end move.b (a0)+,(a1)+ beq.s .end move.b (a0)+,(a1)+ beq.s .end move.b (a0)+,(a1)+ bne.s .loop .end rts |
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20 January 2017, 10:50 | #34 |
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Well, with
Code:
m68k-amigaos-gcc -S -O3 strcpy.c -fomit-frame-pointer -funroll-all-loops Code:
_strcpy: movel sp@(4),a1 movel sp@(8),a0 movel a1,d1 L2: moveb a0@+,d0 moveb d0,a1@+ jeq L12 moveb a0@+,d0 moveb d0,a1@+ jeq L12 moveb a0@+,d0 moveb d0,a1@+ jeq L12 moveb a0@+,d0 moveb d0,a1@+ jeq L12 moveb a0@+,d0 moveb d0,a1@+ jeq L12 moveb a0@+,d0 moveb d0,a1@+ jeq L12 moveb a0@+,d0 moveb d0,a1@+ jeq L12 moveb a0@+,d0 moveb d0,a1@+ jne L2 .even L12: movel d1,d0 rts Code:
moveb a0@+,d0 moveb d0,a1@+ |
20 January 2017, 11:20 | #35 |
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not that i understand much but for the sake of it, results of both aros68k compilers im currently using:
strcpy: move.l 4(%sp),%d0 | dst, dst move.l 8(%sp),%a1 | src, src move.l %d0,%a0 | dst, ivtmp.11 .L2: move.b (%a1)+,%d1 | MEM[base: src_8, offset: 4294967295B], _9 move.b %d1,(%a0)+ | _9, MEM[base: _14, offset: 0B] jne .L2 | rts .size strcpy, .-strcpy .ident "GCC: (GNU) 6.1.0" strcpy: move.l 4(%sp),%d0 | dst, dst move.l 8(%sp),%a1 | src, ivtmp.9 move.l %d0,%a0 | dst, dst .L2: move.b (%a1)+,%d1 | MEM[base: D.779_19, offset: 0B], D.759 move.b %d1,(%a0)+ | D.759, MEM[base: dst_1, offset: 0B] jne .L2 | rts .size strcpy, .-strcpy .ident "GCC: (GNU) 4.6.4" |
20 January 2017, 14:13 | #36 |
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20 January 2017, 17:15 | #37 |
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20 January 2017, 17:20 | #38 |
Total Chaos forever!
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20 January 2017, 18:01 | #39 | ||
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Quote:
Quote:
D0 is the return value. On 68020s and 68030s taken branches are 8 cycles, not taken byte branches are 4 cycles. |
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20 January 2017, 18:24 | #40 | ||
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Quote:
Quote:
@wawa The aros68k GCC compiler is doing a good job here. It should be able to merge 2 lines inside the loop but overall good. strcpy() returns a pointer to the destination. The return is rarely used because it is already available and doesn't change but that is how it is defined. Code:
char *strcpy(char *dst, const char *src); Code:
char *stpcpy(char *dst, const char *src); char *stpcpy(char *dst, const char *src) { while (*dst++ = *src++); return (dst-1); } Last edited by matthey; 20 January 2017 at 18:34. |
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