Am 13.12.19 um 12:25 schrieb Richard Sandiford:
Georg-Johann Lay <avr@xxxxxxxx> writes:Hi, gcc generates wrong code when it aliases symbols like in (For a complete test cases cf. PR92606): static const __attribute((progmem)) int xyz_prog[] = { 123, 123, 123 }; int xyz[] = { 123, 123, 123 }; for target avr. xyz and xyz_prog are binary the same, but the program accesses them with different instructions (LPM for the 1st to read from flash, LD in the 2nd case to read from RAM). The bug is that the compiler issues .section .progmem.data,"a",@progbits .type xyz_prog, @object .size xyz_prog, 12 xyz_prog: .byte 123 ... .set xyz,xyz_prog which is obviously wrong because the symbols MUST NOT alias each other. As I failed to find the target hook that disables such aliasing; please would someone point me to it?I agree it doesn't look like there is one. Sounds like a useful hook to add though.
Ok, I added a respective tree-optimization bug: https://gcc.gnu.org/PR92932 Johann
Thanks, RichardJohann FYI, the generated code is also wrong with names address spaces: static const __flash int xyz_prog[] = { 123, 123, 123 }; int xyz[] = { 123, 123, 123 }; again, PR92606 has a test case: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92606#c3
