Got the 'blinking led' working on the 5529... tried to test the thing
with the large model (-mlarge to every msp430-elf-gcc invocation).
Well, nothing happened. It hangs before main. Exactly in frame_dummy, from
crtbegin.o (built from the mess in libgcc/crtstuff.c). I dumped the files from
the compiler build (found in lib/gcc/msp430-elf/4.9.0/430x/large) so it
shouldn't be something from my test program...
The source code has this fragment:
if (__register_frame_info)
__register_frame_info (__EH_FRAME_BEGIN__, &object);
In small model the object code is like this:
0000009e <frame_dummy>:
9e: 3e 40 00 00 mov #0, r14 ;
a0: R_MSP430_16_BYTE __register_frame_info
a2: 0e 93 cmp #0, r14 ;r3 As==00
a4: 00 24 jz $+2 ;abs 0xa6
a4: R_MSP430_10_PCREL .L32
a6: 3c 40 00 00 mov #0, r12 ;
a8: R_MSP430_16_BYTE .eh_frame
aa: 3d 40 00 00 mov #0, r13 ;
ac: R_MSP430_16_BYTE .bss+0x4
ae: 8e 12 call r14 ;
000000b0 <.L32>:
__register_frame_info is a weak external, which is undefined, so the linker
'locates' it to 0. The result is
00004524 <frame_dummy>:
4524: 3e 40 00 00 mov #0, r14 ; <<< HERE IS LOCATED
4528: 0e 93 cmp #0, r14 ;r3 As==00
452a: 05 24 jz $+12 ;abs 0x4536
452c: 3c 40 04 44 mov #17412, r12 ;#0x4404
4530: 3d 40 82 24 mov #9346, r13 ;#0x2482
4534: 8e 12 call r14 ;
00004536 <.L32>:
Here zero is obviously zero, so the call is skipped (as intended:D)
When linking the large model crtbegin.o, the generated code is really different:
0000015e <frame_dummy>:
15e: 8c 00 00 00 mova #0, r12 ;
15e: R_MSP430X_ABS20_ADR_SRC .eh_frame
162: 8d 00 00 00 mova #0, r13 ;
162: R_MSP430X_ABS20_ADR_SRC .bss+0x6
166: b0 13 00 00 calla #0 ;0x00000
166: R_MSP430X_ABS20_ADR_DST __register_frame_info
Where is the condition check? Obviously after location the result is this:
000045fe <frame_dummy>:
45fe: 8c 00 08 44 mova #17416, r12 ;0x04408
4602: 8d 00 f2 24 mova #9458, r13 ;0x024f2
4606: b0 13 00 00 calla #0 ;0x00000 << HERE IS
LOCATED
That calla #0 doesn't seem very legal to me...
So... is this expected, it's a known bug or needs to be reported? (and where) I
know that 20-bit support is beta (I built it from trunk...) so I'm not worrying
too much.
Suggestions appreciated
--
Lorenzo Marcantonio
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