https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86005
Alex Bradbury <asb at lowrisc dot org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |asb at lowrisc dot org
Summary|[RISCV] Invalid lowering of |[RISCV] Invalid intermixing
|atomics for -march=rv32i / |of __atomic_* libcalls and
|-march=rv64i |inline atomic instruction
| |sequences
--- Comment #1 from Alex Bradbury <asb at lowrisc dot org> ---
Actually I think this bug is wider in scope than I first thought. GCC will also
intermix __atomic libcalls and inline instruction sequences with -march=rv32ia
when values less than XLEN in size are accessed.
$ cat foo.c
char atomic(char *i) {
char j = __atomic_add_fetch(i, 1, __ATOMIC_SEQ_CST);
char k;
__atomic_load(i, &k, __ATOMIC_SEQ_CST);
return j+k;
}
$ ./riscv32-unknown-elf-gcc -march=rv32ia foo.c -O1 -S -o -
.file "foo.c"
.option nopic
.text
.align 2
.globl atomic
.type atomic, @function
atomic:
addi sp,sp,-16
sw ra,12(sp)
sw s0,8(sp)
mv s0,a0
li a2,5
li a1,1
call __atomic_fetch_add_1
addi a0,a0,1
andi a0,a0,0xff
fence iorw,iorw
lbu a5,0(s0)
fence iorw,iorw
add a0,a0,a5
andi a0,a0,0xff
lw ra,12(sp)
lw s0,8(sp)
addi sp,sp,16
jr ra
.size atomic, .-atomic
.ident "GCC: (GNU) 9.0.0 20180530 (experimental)"
