I am trying to build a temperature control application for a 68000 processor. I am currently using GCC 8.2.0. I am compiling with the -msoft-float flag. However, the floating point library routines appear to be broken. Example:
'000174f4 <__ltdf2>:'
'174f4: 4e56 0000 linkw %fp,#0'
'174f8: 4878 0001 pea 1 <ADD>'
'174fc: 2f2e 0014 movel %fp@(20),%sp@-'
'17500: 2f2e 0010 movel %fp@(16),%sp@-'
'17504: 2f2e 000c movel %fp@(12),%sp@-'
'17508: 2f2e 0008 movel %fp@(8),%sp@-'
'1750c: 61ff bsrs 1750d <__ltdf2+0x19>'
'1750e: ffff .short 0xffff'
'17510: fd94 .short 0xfd94'
'17512: 4e5e unlk %fp'
'17514: 4e75 rts'
'17516: 4e71 nop'
Can someone explain why this code is generated or what is happening here? No way will a 68000 branch to an odd address.
UPDATE I've been digging into this, and the problem appears to be injected during linking. Dumping the code for this function from libgcc.a shows the following:
`00000000 <__ltdf2>:`
` 0: 4e56 0000 linkw %fp,#0`
`4: 4878 0001 pea 1 <__ltdf2+0x1>`
` 8: 2f2e 0014 movel %fp@(20),%sp@-`
` c: 2f2e 0010 movel %fp@(16),%sp@-`
`10: 2f2e 000c movel %fp@(12),%sp@-`
`14: 2f2e 0008 movel %fp@(8),%sp@-`
`18: 61ff 0000 0000 bsrl 1a <__ltdf2+0x1a>`
`1e: 4e5e unlk %fp`
` 20: 4e75 rts`
So the linker must be trying to fill in the branch offset and messing up. Since the source for this function is a string of macros, I'm not sure where it really wanted to branch to.
