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5687a376df
I noticed that unaligned accesses were returning garbage values.
Give test data like this:
char testdata[] = { 0x12, 0x34, 0x56, 0x78, 0x9a, 0xbc, 0xde, 0xf1, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef, 0x5a };
Iterating through uint32_t space 1 byte at a time should
look like this:
freebsd-carambola2:/mnt# ./test
Hello, world!
offset 0 pointer 0x410b00 value 0x12345678 0x12345678
offset 1 pointer 0x410b01 value 0x3456789a 0x3456789a
offset 2 pointer 0x410b02 value 0x56789abc 0x56789abc
offset 3 pointer 0x410b03 value 0x789abcde 0x789abcde
offset 4 pointer 0x410b04 value 0x9abcdef1 0x9abcdef1
offset 5 pointer 0x410b05 value 0xbcdef123 0xbcdef123
offset 6 pointer 0x410b06 value 0xdef12345 0xdef12345
offset 7 pointer 0x410b07 value 0xf1234567 0xf1234567
.. but to begin with it looked like this:
offset 0 value 0x12345678
offset 1 value 0x00410a9a
offset 2 value 0x00419abc
offset 3 value 0x009abcde
offset 4 value 0x9abcdef1
offset 5 value 0x00410a23
offset 6 value 0x00412345
offset 7 value 0x00234567
The amusing reason? The compiler is generating the lwr/lwl incorrectly.
Here's an example after I tried to replace the two macros with a single
invocation and offset, rather than having the compiler compile in addiu
to s3 - but the bug is the same:
1044: 8a620003 lwl v0,0(s3)
1048: 9a730000 lwr s3,3(s3)
.. which is just totally trashy and wrong.
This explicitly tells the compiler to treat the output as being read
and written to, which is what lwl/lwr does with the destination
register.
I think a subsequent commit should unify these macros to skip an addiu,
but that can be a later commit.
Reviewed by: jhb
Differential Revision: https://reviews.freebsd.org/D25040
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| .. | ||
| autoconf.c | ||
| bcopy.S | ||
| bus_space_generic.c | ||
| busdma_machdep.c | ||
| cache.c | ||
| cache_mipsNN.c | ||
| cpu.c | ||
| db_disasm.c | ||
| db_interface.c | ||
| db_trace.c | ||
| dump_machdep.c | ||
| elf_machdep.c | ||
| elf_trampoline.c | ||
| exception.S | ||
| fp.S | ||
| freebsd32_machdep.c | ||
| gdb_machdep.c | ||
| genassym.c | ||
| in_cksum.c | ||
| inckern.S | ||
| intr_machdep.c | ||
| libkern_machdep.c | ||
| locore.S | ||
| machdep.c | ||
| mem.c | ||
| minidump_machdep.c | ||
| mips_pic.c | ||
| mp_machdep.c | ||
| mpboot.S | ||
| nexus.c | ||
| octeon_cop2.c | ||
| octeon_cop2_swtch.S | ||
| ofw_machdep.c | ||
| pm_machdep.c | ||
| pmap.c | ||
| ptrace_machdep.c | ||
| sc_machdep.c | ||
| stack_machdep.c | ||
| stdatomic.c | ||
| support.S | ||
| swtch.S | ||
| sys_machdep.c | ||
| tick.c | ||
| tlb.c | ||
| trap.c | ||
| uio_machdep.c | ||
| uma_machdep.c | ||
| vm_machdep.c | ||