aarch64: Specify that FEAT_MOPS sequences clobber CC
According to the architecture pseudocode the FEAT_MOPS sequences overwrite the NZCV flags
as par of their operation, so GCC needs to model that in the relevant RTL patterns.
For the testcase:
void g();
void foo (int a, size_t N, char *__restrict__ in,
char *__restrict__ out)
{
if (a != 3)
__builtin_memcpy (out, in, N);
if (a > 3)
g ();
}
we will currently generate:
foo:
cmp w0, 3
bne .L6
.L1:
ret
.L6:
cpyfp [x3]!, [x2]!, x1!
cpyfm [x3]!, [x2]!, x1!
cpyfe [x3]!, [x2]!, x1!
ble .L1 // Flags reused after CPYF* sequence
b g
This is wrong as the result of cmp needs to be recalculated after the MOPS sequence.
With this patch we'll insert a "cmp w0, 3" before the ble, similar to what clang does.
Bootstrapped and tested on aarch64-none-linux-gnu.
Pushing to trunk and to the GCC 12 branch after some baking time.
gcc/ChangeLog:
* config/aarch64/aarch64.md (aarch64_cpymemdi): Specify clobber of CC reg.
(*aarch64_cpymemdi): Likewise.
(aarch64_movmemdi): Likewise.
(aarch64_setmemdi): Likewise.
(*aarch64_setmemdi): Likewise.
gcc/testsuite/ChangeLog:
* gcc.target/aarch64/mops_5.c: New test.
* gcc.target/aarch64/mops_6.c: Likewise.
* gcc.target/aarch64/mops_7.c: Likewise.