LTO in mspgcc is untested; if it works for you, great, but I have no plans
to enable or support it in mspgcc. Future LTO support would have to be
part of the new toolchain being provided by Red Hat. (Presumably main gets
lost because it's placed in a special section that LTO wouldn't know about.)
Peter
On Wed, Dec 26, 2012 at 3:14 PM, Matthew Tan Creti <mtanc...@purdue.edu>wrote:
> Hi,
>
> I have searched the web for using lto with mspgcc, and it appears that
> it is not yet officially supported. However, minus one minor bug it does
> appear to work. The bug is if main is included in the lto then main does
> not show up in the binary. The obvious workaround is to place a wrapper
> around main. I give an example of what I mean below. The example shows
> that inlining across object files works (specifically the externally
> defined get_value is inlined in sub_main). It was compiled with
> mspgcc-20120911.
>
> Can anyone comment further on the state of lto support in mspgcc? Are
> there any show stoppers I am likely to encounter when trying to compile
> more complex code than this simple example?
>
> Thanks,
> Matt
>
> Makefile
> 01 CC=/usr/mspgcc-4.7.0/bin/msp430-gcc
> 02 COMPILE_FLAGS+= -mmcu=msp430f1611 -O -Os -mmpy=none -Wall -Wshadow
> 03
> 04 main.firmware: main.o sub_main.o inlineable_functions.o
> 05 $(CC) $(COMPILE_FLAGS) -flto -o $@ $^
> 06 main.o: main.c
> 07 $(CC) $(COMPILE_FLAGS) -c $^
> 08 sub_main.o: sub_main.c
> 09 $(CC) $(COMPILE_FLAGS) -flto -c $^
> 10 inlineable_functions.o: inlineable_functions.c
> 11 $(CC) $(COMPILE_FLAGS) -flto -c $^
>
> main.c
> 01 extern int sub_main(void);
> 02 int main(void) {
> 03 return sub_main();
> 04 }
>
> sub_main.c
> 01 extern int get_value(int i);
> 02 int sub_main(void) {
> 03 *((unsigned int*)200) = get_value(0);
> 04 return 0;
> 05 }
>
> inlineable_functions.c
> 01 int get_value(int i) {
> 02 return i + 10;
> 03 }
>
> main.firmware: file format elf32-msp430
> Disassembly of section .text:
> 00004000 <__watchdog_support>:
> 4000: 55 42 20 01 mov.b &0x0120,r5
> 4004: 35 d0 08 5a bis #23048, r5 ;#0x5a08
> 4008: 82 45 00 11 mov r5, &0x1100
> 0000400c <__init_stack>:
> 400c: 31 40 00 39 mov #14592, r1 ;#0x3900
> 00004010 <__do_copy_data>:
> 4010: 3f 40 00 00 mov #0, r15 ;#0x0000
> 4014: 0f 93 tst r15
> 4016: 08 24 jz $+18 ;abs 0x4028
> 4018: 92 42 00 11 mov &0x1100,&0x0120
> 401c: 20 01
> 401e: 2f 83 decd r15
> 4020: 9f 4f 58 40 mov 16472(r15),4352(r15);0x4058(r15),
> 0x1100(r15)
> 4024: 00 11
> 4026: f8 23 jnz $-14 ;abs 0x4018
> 00004028 <__do_clear_bss>:
> 4028: 3f 40 00 00 mov #0, r15 ;#0x0000
> 402c: 0f 93 tst r15
> 402e: 07 24 jz $+16 ;abs 0x403e
> 4030: 92 42 00 11 mov &0x1100,&0x0120
> 4034: 20 01
> 4036: 1f 83 dec r15
> 4038: cf 43 00 11 mov.b #0, 4352(r15);r3 As==00,
> 0x1100(r15)
> 403c: f9 23 jnz $-12 ;abs 0x4030
> 0000403e <main>:
> 403e: b0 12 4c 40 call #0x404c
> 00004042 <__stop_progExec__>:
> 4042: 32 d0 f0 00 bis #240, r2 ;#0x00f0
> 4046: fd 3f jmp $-4 ;abs 0x4042
> 00004048 <__ctors_end>:
> 4048: 30 40 56 40 br #0x4056
> 0000404c <sub_main>:
> 404c: b2 40 0a 00 mov #10, &0x00c8 ;#0x000a
> 4050: c8 00
> 4052: 0f 43 clr r15
> 4054: 30 41 ret
> 00004056 <_unexpected_>:
> 4056: 00 13 reti
>
>
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